aboutsummaryrefslogtreecommitdiff
path: root/en_US.ISO8859-1/books/handbook/basics/chapter.xml
blob: 587749831b2b7d7e4ad6cad841b74c54f7a30c23 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
<?xml version="1.0" encoding="iso-8859-1" standalone="no"?>
<!--
     The FreeBSD Documentation Project

     $FreeBSD$
-->

<chapter id="basics">
  <chapterinfo>
    <authorgroup>
      <author>
        <firstname>Chris</firstname>
	<surname>Shumway</surname>
	<contrib>Rewritten by </contrib>
      </author>
    </authorgroup>
    <!-- 10 Mar 2000 -->
  </chapterinfo>

  <title>UNIX Basics</title>

  <sect1 id="basics-synopsis">
    <title>Synopsis</title>

   <para>The following chapter will cover the basic commands and
     functionality of the FreeBSD operating system.  Much of this
     material is relevant for any &unix;-like operating system.  Feel
     free to skim over this chapter if you are familiar with the
     material.  If you are new to FreeBSD, then you will definitely
     want to read through this chapter carefully.</para>

    <para>After reading this chapter, you will know:</para>

    <itemizedlist>
      <listitem>
        <para>How to use the <quote>virtual consoles</quote> of
	  FreeBSD.</para>
      </listitem>
      <listitem>
	<para>How &unix; file permissions work along with
	  understanding file flags in &os;.</para>
      </listitem>
      <listitem>
	<para>The default &os; file system layout.</para>
      </listitem>
      <listitem>
	<para>The &os; disk organization.</para>
      </listitem>
      <listitem>
	<para>How to mount and unmount file systems.</para>
      </listitem>
      <listitem>
	<para>What processes, daemons, and signals are.</para>
      </listitem>
      <listitem>
	<para>What a shell is, and how to change your default login
	environment.</para>
      </listitem>
      <listitem>
	<para>How to use basic text editors.</para>
      </listitem>
      <listitem>
	<para>What devices and device nodes are.</para>
      </listitem>
      <listitem>
	<para>What binary format is used under &os;.</para>
      </listitem>
      <listitem>
	<para>How to read manual pages for more information.</para>
      </listitem>
    </itemizedlist>

  </sect1>

  <sect1 id="consoles">
    <title>Virtual Consoles and Terminals</title>
    <indexterm><primary>virtual consoles</primary></indexterm>
    <indexterm><primary>terminals</primary></indexterm>

    <para>FreeBSD can be used in various ways.  One of them is typing commands
      to a text terminal.  A lot of the flexibility and power of a &unix;
      operating system is readily available at your hands when using FreeBSD
      this way.  This section describes what <quote>terminals</quote> and
      <quote>consoles</quote> are, and how you can use them in FreeBSD.</para>

    <sect2 id="consoles-intro">
      <title>The Console</title>
      <indexterm><primary>console</primary></indexterm>

      <para>If you have not configured FreeBSD to automatically start a
	graphical environment during startup, the system will present you with
	a login prompt after it boots, right after the startup scripts finish
	running.  You will see something similar to:</para>

      <screen>Additional ABI support:.
Local package initialization:.
Additional TCP options:.

Fri Sep 20 13:01:06 EEST 2002

FreeBSD/i386 (pc3.example.org) (ttyv0)

login:</screen>

      <para>The messages might be a bit different on your system, but you will
	see something similar.  The last two lines are what we are interested
	in right now.  The second last line reads:</para>

      <programlisting>FreeBSD/i386 (pc3.example.org) (ttyv0)</programlisting>

      <para>This line contains some bits of information about the system you
        have just booted.  You are looking at a <quote>FreeBSD</quote>
	console, running on an Intel or compatible processor of the x86
	architecture<footnote>
	  <para>This is what <literal>i386</literal> means.  Note that even if
	    you are not running FreeBSD on an Intel 386 CPU, this is going to
	    be <literal>i386</literal>.  It is not the type of your processor,
	    but the processor <quote>architecture</quote> that is shown
	    here.</para>
	</footnote>.  The name of this machine (every &unix; machine has a
	name) is <hostid>pc3.example.org</hostid>, and you are now looking
	at its system console&mdash;the <devicename>ttyv0</devicename>
	terminal.</para>

      <para>Finally, the last line is always:</para>

      <programlisting>login:</programlisting>

      <para>This is the part where you are supposed to type in your
	<quote>username</quote> to log into FreeBSD.  The next section
	describes how you can do this.</para>
    </sect2>

    <sect2 id="consoles-login">
      <title>Logging into FreeBSD</title>

      <para>FreeBSD is a multiuser, multiprocessing system.  This is
	the formal description that is usually given to a system that can be
	used by many different people, who simultaneously run a lot of
	programs on a single machine.</para>

      <para>Every multiuser system needs some way to distinguish one
	<quote>user</quote> from the rest.  In FreeBSD (and all the
	&unix;-like operating systems), this is accomplished by requiring that
	every user must <quote>log into</quote> the system before being able
	to run programs.  Every user has a unique name (the
	<quote>username</quote>) and a personal, secret key (the
	<quote>password</quote>).  FreeBSD will ask for these two before
	allowing a user to run any programs.</para>

      <indexterm><primary>startup scripts</primary></indexterm>
      <para>Right after FreeBSD boots and finishes running its startup
	scripts<footnote>
	  <para>Startup scripts are programs that are run automatically by
	    FreeBSD when booting.  Their main function is to set things up for
	    everything else to run, and start any services that you have
	    configured to run in the background doing useful things.</para>
	</footnote>, it will present you with a prompt and ask for a valid
	username:</para>

      <screen>login:</screen>

      <para>For the sake of this example, let us assume that your username is
	<username>john</username>.  Type <literal>john</literal> at this prompt and press
	<keycap>Enter</keycap>.  You should then be presented with a prompt to
	enter a <quote>password</quote>:</para>

      <screen>login: <userinput>john</userinput>
Password:</screen>

      <para>Type in <username>john</username>'s password now, and press
	<keycap>Enter</keycap>.  The password is <emphasis>not
	echoed!</emphasis>  You need not worry about this right now.  Suffice
	it to say that it is done for security reasons.</para>

      <para>If you have typed your password correctly, you should by now be
	logged into FreeBSD and ready to try out all the available
	commands.</para>

      <para>You should see the <acronym>MOTD</acronym> or message of
	the day followed by a command prompt (a <literal>#</literal>,
	<literal>$</literal>, or <literal>%</literal> character).  This
	indicates you have successfully logged into FreeBSD.</para>
    </sect2>

    <sect2 id="consoles-virtual">
      <title>Multiple Consoles</title>

      <para>Running &unix; commands in one console is fine, but FreeBSD can
	run many programs at once.  Having one console where commands can be
	typed would be a bit of a waste when an operating system like FreeBSD
	can run dozens of programs at the same time.  This is where
	<quote>virtual consoles</quote> can be very helpful.</para>

      <para>FreeBSD can be configured to present you with many different
	virtual consoles.  You can switch from one of them to any other
	virtual console by pressing a couple of keys on your keyboard.  Each
	console has its own different output channel, and FreeBSD takes care
	of properly redirecting keyboard input and monitor output as you
	switch from one virtual console to the next.</para>

      <para>Special key combinations have been reserved by FreeBSD for
	switching consoles<footnote>
	  <para>A fairly technical and accurate description of all the details
	    of the FreeBSD console and keyboard drivers can be found in the
	    manual pages of &man.syscons.4;, &man.atkbd.4;, &man.vidcontrol.1;
	    and &man.kbdcontrol.1;.  We will not expand on the details here,
	    but the interested reader can always consult the manual pages for
	    a more detailed and thorough explanation of how things
	    work.</para>
	</footnote>.  You can use
	<keycombo><keycap>Alt</keycap><keycap>F1</keycap></keycombo>,
	<keycombo><keycap>Alt</keycap><keycap>F2</keycap></keycombo>, through
	<keycombo><keycap>Alt</keycap><keycap>F8</keycap></keycombo> to switch
	to a different virtual console in FreeBSD.</para>

      <para>As you are switching from one console to the next, FreeBSD takes
	care of saving and restoring the screen output.  The result is an
	<quote>illusion</quote> of having multiple <quote>virtual</quote>
	screens and keyboards that you can use to type commands for
	FreeBSD to run.  The programs that you launch on one virtual console
	do not stop running when that console is not visible.  They continue
	running when you have switched to a different virtual console.</para>
    </sect2>

    <sect2 id="consoles-ttys">
      <title>The <filename>/etc/ttys</filename> File</title>

      <para>The default configuration of FreeBSD will start up with eight
        virtual consoles.  This is not a hardwired setting though, and
        you can easily customize your installation to boot with more
        or fewer virtual consoles.  The number and settings of the
        virtual consoles are configured in the
        <filename>/etc/ttys</filename> file.</para>

      <para>You can use the <filename>/etc/ttys</filename> file to configure
	the virtual consoles of FreeBSD.  Each uncommented line in this file
	(lines that do not start with a <literal>#</literal> character) contains
	settings for a single terminal or virtual console.  The default
	version of this file that ships with FreeBSD configures nine virtual
	consoles, and enables eight of them.  They are the lines that start with
	<literal>ttyv</literal>:</para>

      <programlisting># name  getty                           type    status          comments
#
ttyv0   "/usr/libexec/getty Pc"         cons25  on  secure
# Virtual terminals
ttyv1   "/usr/libexec/getty Pc"         cons25  on  secure
ttyv2   "/usr/libexec/getty Pc"         cons25  on  secure
ttyv3   "/usr/libexec/getty Pc"         cons25  on  secure
ttyv4   "/usr/libexec/getty Pc"         cons25  on  secure
ttyv5   "/usr/libexec/getty Pc"         cons25  on  secure
ttyv6   "/usr/libexec/getty Pc"         cons25  on  secure
ttyv7   "/usr/libexec/getty Pc"         cons25  on  secure
ttyv8   "/usr/X11R6/bin/xdm -nodaemon"  xterm   off secure</programlisting>

      <para>For a detailed description of every column in this file and all
	the options you can use to set things up for the virtual consoles,
	consult the &man.ttys.5; manual page.</para>
    </sect2>

    <sect2 id="consoles-singleuser">
      <title>Single User Mode Console</title>

      <para>A detailed description of what <quote>single user mode</quote> is
	can be found in <xref linkend="boot-singleuser"/>.  It is worth noting
	that there is only one console when you are running FreeBSD in single
	user mode.  There are no virtual consoles available.  The settings of
	the single user mode console can also be found in the
	<filename>/etc/ttys</filename> file.  Look for the line that starts
	with <literal>console</literal>:</para>

      <programlisting># name  getty                           type    status          comments
#
# If console is marked "insecure", then init will ask for the root password
# when going to single-user mode.
console none                            unknown off secure</programlisting>

      <note>
        <para>As the comments above the <literal>console</literal> line
	  indicate, you can edit this line and change <literal>secure</literal> to
	  <literal>insecure</literal>.  If you do that, when FreeBSD boots
	  into single user mode, it will still ask for the
	  <username>root</username> password.</para>

	<para><emphasis>Be careful when changing this to
	  <literal>insecure</literal></emphasis>.  If you ever forget
	  the <username>root</username> password, booting into single user
	  mode is a bit involved.  It is still possible, but it might be a bit
	  hard for someone who is not very comfortable with the FreeBSD
	  booting process and the programs involved.</para>
      </note>
    </sect2>

    <sect2 id="consoles-vidcontrol">
      <title>Changing Console Video Modes</title>

      <para>The FreeBSD console default video mode may be adjusted to
	1024x768, 1280x1024, or any other size supported by your
	graphics chip and monitor.  To use a different video mode, you
	first must recompile your kernel and include two additional
	options:</para>

      <programlisting>options VESA
options SC_PIXEL_MODE</programlisting>

      <para>Once the kernel has been recompiled with these two
	options, you can then determine what video modes are supported
	by your hardware by using the &man.vidcontrol.1; utility.  To
	get a list of supported video modes issue the following:</para>

      <screen>&prompt.root; <userinput>vidcontrol -i mode</userinput></screen>

      <para>The output of this command is a list of video modes that
	are supported by your hardware.  You can then choose to use a
	new video mode by passing it to &man.vidcontrol.1; in a <username>root</username> console:</para>

      <screen>&prompt.root; <userinput>vidcontrol MODE_279</userinput></screen>

      <para>If the new video mode is acceptable, it can be permanently
	set on boot by setting it in the <filename>/etc/rc.conf</filename>
	file:</para>

      <programlisting>allscreens_flags="MODE_279"</programlisting>
    </sect2>
  </sect1>

  <sect1 id="permissions">
    <title>Permissions</title>
    <indexterm><primary>UNIX</primary></indexterm>

    <para>FreeBSD, being a direct descendant of BSD &unix;, is based on
      several key &unix; concepts.  The first and
      most pronounced is that FreeBSD is a multi-user operating system.
      The system can handle several users all working simultaneously on
      completely unrelated tasks.  The system is responsible for properly
      sharing and managing requests for hardware devices, peripherals,
      memory, and CPU time fairly to each user.</para>

    <para>Because the system is capable of supporting multiple users,
      everything the system manages has a set of permissions governing who
      can read, write, and execute the resource.  These permissions are
      stored as three octets broken into three pieces, one for the owner of
      the file, one for the group that the file belongs to, and one for
      everyone else.  This numerical representation works like
      this:</para>

    <indexterm><primary>permissions</primary></indexterm>
    <indexterm>
      <primary>file permissions</primary>
    </indexterm>
    <informaltable frame="none" pgwide="1">
      <tgroup cols="3">
	<thead>
	  <row>
	    <entry>Value</entry>
	    <entry>Permission</entry>
	    <entry>Directory Listing</entry>
	  </row>
	</thead>

	<tbody>
	  <row>
	    <entry>0</entry>
	    <entry>No read, no write, no execute</entry>
	    <entry><literal>---</literal></entry>
	  </row>

	  <row>
	    <entry>1</entry>
	    <entry>No read, no write, execute</entry>
	    <entry><literal>--x</literal></entry>
	  </row>

	  <row>
	    <entry>2</entry>
	    <entry>No read, write, no execute</entry>
	    <entry><literal>-w-</literal></entry>
	  </row>

	  <row>
	    <entry>3</entry>
	    <entry>No read, write, execute</entry>
	    <entry><literal>-wx</literal></entry>
	  </row>

	  <row>
	    <entry>4</entry>
	    <entry>Read, no write, no execute</entry>
	    <entry><literal>r--</literal></entry>
	  </row>

	  <row>
	    <entry>5</entry>
	    <entry>Read, no write, execute</entry>
	    <entry><literal>r-x</literal></entry>
	  </row>

	  <row>
	    <entry>6</entry>
	    <entry>Read, write, no execute</entry>
	    <entry><literal>rw-</literal></entry>
	  </row>

	  <row>
	    <entry>7</entry>
	    <entry>Read, write, execute</entry>
	    <entry><literal>rwx</literal></entry>
	  </row>
	</tbody>
      </tgroup>
    </informaltable>
    <indexterm>
      <primary><command>ls</command></primary>
    </indexterm>
    <indexterm><primary>directories</primary></indexterm>

    <para>You can use the <option>-l</option> command line
      argument to &man.ls.1; to view a long directory listing that
      includes a column with information about a file's permissions
      for the owner, group, and everyone else.  For example, a
      <command>ls -l</command> in an arbitrary directory may show:</para>

    <screen>&prompt.user; <userinput>ls -l</userinput>
total 530
-rw-r--r--  1 root  wheel     512 Sep  5 12:31 myfile
-rw-r--r--  1 root  wheel     512 Sep  5 12:31 otherfile
-rw-r--r--  1 root  wheel    7680 Sep  5 12:31 email.txt
...</screen>

    <para>Here is how the first column of <command>ls -l</command> is
      broken up:</para>

    <screen>-rw-r--r--</screen>

    <para>The first (leftmost) character
      tells if this file is a regular file, a directory, a special
      character device, a socket, or any other special
      pseudo-file device.  In this case, the <literal>-</literal>
      indicates a regular file.  The next three characters,
      <literal>rw-</literal> in this example, give the permissions for the owner of the
      file.  The next three characters, <literal>r--</literal>, give the
      permissions for the group that the file belongs to.  The final three
      characters, <literal>r--</literal>, give the permissions for the
      rest of the world.  A dash means that the permission is turned off.
      In the case of this file, the permissions are set so the owner can
      read and write to the file, the group can read the file, and the
      rest of the world can only read the file.  According to the table
      above, the permissions for this file would be
      <literal>644</literal>, where each digit represents the three parts
      of the file's permission.</para>

    <para>This is all well and good, but how does the system control
      permissions on devices? FreeBSD actually treats most hardware
      devices as a file that programs can open, read, and write data to
      just like any other file.  These special device files are stored on
      the <filename>/dev</filename> directory.</para>

    <para>Directories are also treated as files.  They have read, write,
      and execute permissions.  The executable bit for a directory has a
      slightly different meaning than that of files.  When a directory is
      marked executable, it means it can be traversed into, that is, it is
      possible to <quote>cd</quote> (change directory) into it.  This also means that
      within the directory it is possible to access files whose names are
      known (subject, of course, to the permissions on the files
      themselves).</para>

    <para>In particular, in order to perform a directory listing,
      read permission must be set on the directory, whilst to delete a file
      that one knows the name of, it is necessary to have write
      <emphasis>and</emphasis> execute permissions to the directory
      containing the file.</para>

    <para>There are more permission bits, but they are primarily used in
      special circumstances such as setuid binaries and sticky
      directories.  If you want more information on file permissions and
      how to set them, be sure to look at the &man.chmod.1; manual
      page.</para>

    <sect2>
      <sect2info>
	<authorgroup>
	  <author>
	    <firstname>Tom</firstname>
	    <surname>Rhodes</surname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
      </sect2info>

      <title>Symbolic Permissions</title>
      <indexterm><primary>permissions</primary><secondary>symbolic</secondary></indexterm>

      <para>Symbolic permissions, sometimes referred to as symbolic expressions,
	use characters in place of octal values to assign permissions to files
	or directories.  Symbolic expressions use the syntax of (who) (action)
	(permissions), where the following values are available:</para>

      <informaltable frame="none" pgwide="1">
	<tgroup cols="3">
	  <thead>
	    <row>
	      <entry>Option</entry>
	      <entry>Letter</entry>
	      <entry>Represents</entry>
	    </row>
	  </thead>

	<tbody>
	  <row>
	    <entry>(who)</entry>
	    <entry>u</entry>
	    <entry>User</entry>
	  </row>

	  <row>
	    <entry>(who)</entry>
	    <entry>g</entry>
	    <entry>Group owner</entry>
	  </row>

	  <row>
	    <entry>(who)</entry>
	    <entry>o</entry>
	    <entry>Other</entry>
	  </row>

	  <row>
	    <entry>(who)</entry>
	    <entry>a</entry>
	    <entry>All (<quote>world</quote>)</entry>
	  </row>

	  <row>
	    <entry>(action)</entry>
	    <entry>+</entry>
	    <entry>Adding permissions</entry>
	  </row>

	  <row>
	    <entry>(action)</entry>
	    <entry>-</entry>
	    <entry>Removing permissions</entry>
	  </row>

	  <row>
	    <entry>(action)</entry>
	    <entry>=</entry>
	    <entry>Explicitly set permissions</entry>
	  </row>

	  <row>
	    <entry>(permissions)</entry>
	    <entry>r</entry>
	    <entry>Read</entry>
	  </row>

	  <row>
	    <entry>(permissions)</entry>
	    <entry>w</entry>
	    <entry>Write</entry>
	  </row>

	  <row>
	    <entry>(permissions)</entry>
	    <entry>x</entry>
	    <entry>Execute</entry>
	  </row>

	  <row>
	    <entry>(permissions)</entry>
	    <entry>t</entry>
	    <entry>Sticky bit</entry>
	  </row>

	  <row>
	    <entry>(permissions)</entry>
	    <entry>s</entry>
	    <entry>Set UID or GID</entry>
	  </row>
	</tbody>
      </tgroup>
    </informaltable>

    <para>These values are used with the &man.chmod.1; command
      just like before, but with letters.  For an example, you could use
      the following command to block other users from accessing
      <replaceable>FILE</replaceable>:</para>

    <screen>&prompt.user; <userinput>chmod go= FILE</userinput></screen>

    <para>A comma separated list can be provided when more than one set
      of changes to a file must be made.  For example the following command
      will remove the group and <quote>world</quote> write permission
      on <replaceable>FILE</replaceable>, then it adds the execute
      permissions for everyone:</para>

    <screen>&prompt.user; <userinput>chmod go-w,a+x <replaceable>FILE</replaceable></userinput></screen>

<!--
    <para>Most users will not notice this, but it should be pointed out
      that using the octal method will only set or assign permissions to
      a file; it does not add or delete them.</para>
-->
    </sect2>

    <sect2>
      <sect2info>
	<authorgroup>
	  <author>
	    <firstname>Tom</firstname>
	    <surname>Rhodes</surname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
      </sect2info>

      <title>&os; File Flags</title>

      <para>In addition to file permissions discussed previously, &os;
	supports the use of <quote>file flags.</quote>  These flags
	add an additional level of security and control over files, but
	not directories.</para>

      <para>These file flags add an additional level of control over
	files, helping to ensure that in some cases not even the
	<username>root</username> can remove or alter files.</para>

      <para>File flags are altered by using the &man.chflags.1; utility,
	using a simple interface.  For example, to enable the system
	undeletable flag on the file <filename>file1</filename>,
	issue the following command:</para>

      <screen>&prompt.root; <userinput>chflags sunlink <filename>file1</filename></userinput></screen>

      <para>And to disable the system undeletable flag,
	issue the previous command with <quote>no</quote> in
	front of the <option>sunlink</option>.  Observe:</para>

      <screen>&prompt.root; <userinput>chflags nosunlink <filename>file1</filename></userinput></screen>

      <para>To view the flags of this file, use the &man.ls.1; command
	with the <option>-lo</option> flags:</para>

      <screen>&prompt.root; <userinput>ls -lo <filename>file1</filename></userinput></screen>

      <para>The output should look like the following:</para>

      <programlisting>-rw-r--r--  1 trhodes  trhodes  sunlnk 0 Mar  1 05:54 file1</programlisting>

      <para>Several flags may only added or removed to files by the
	<username>root</username> user.  In other cases, the file owner
	may set these flags.  It is recommended that administrators read
	over the &man.chflags.1; and &man.chflags.2; manual pages for
	more information.</para>
    </sect2>

    <sect2>
      <sect2info>
	<authorgroup>
	  <author>
	    <firstname>Tom</firstname>
	    <surname>Rhodes</surname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
      </sect2info>

      <title>The setuid, setgid, and sticky Permissions</title>

      <para>Other than the permissions already discussed, there are
	three other specific settings that all administrators should
	know about.  They are the <literal>setuid</literal>,
	<literal>setgid</literal> and <literal>sticky</literal>
	permissions.</para>

      <para>These settings are important for some &unix; operations
	as they provide functionality not normally granted to normal
	users.  To understand them, the difference between the real
	user ID and effective user ID must also be noted.</para>

      <para>The real user ID is the <acronym>UID</acronym> who owns
	or starts the process.  The effective <acronym>UID</acronym>
	is the user ID the process runs as.  As an example, the
	&man.passwd.1; utility runs with the real user ID as the
	user changing their password; however, to manipulate the
	password database, it runs as the effective ID of the
	<username>root</username> user.  This is what allows normal
	users to change their passwords without seeing a
	<errorname>Permission Denied</errorname> error.</para>

      <note>
	<para>The <literal>nosuid</literal> &man.mount.8; option will
	  cause these binaries to silently fail.  That is, they will
	  fail to execute without ever alerting the user.  That option
	  is also not completely reliable as a <literal>nosuid</literal>
	  wrapper may be able to circumvent it; according to the
	  &man.mount.8; manual page.</para>
      </note>

      <para>The setuid permission may be set by prefixing a permission
	set with the number four (4) as shown in the following
	example:</para>

      <screen>&prompt.root; <userinput>chmod 4755 suidexample.sh</userinput></screen>

      <para>The permissions on the
	<filename><replaceable>suidexample.sh</replaceable></filename>
	file should now look like the following:</para>

      <programlisting>-rwsr-xr-x   1 trhodes  trhodes    63 Aug 29 06:36 suidexample.sh</programlisting>

      <para>It should be noticeable from this example that an
	<literal>s</literal> is now part of the permission set
	designated for the file owner, replacing the executable
	bit.  This allows utilities which need elevated permissions,
	such as <command>passwd</command>.</para>

      <para>To view this in real time, open two terminals.  On
	one, start the <command>passwd</command> process as a normal
	user.  While it waits for a new password, check the process
	table and look at the user information of the
	<command>passwd</command> command.</para>

      <para>In terminal A:</para>

      <screen>Changing local password for trhodes
Old Password:</screen>

      <para>In terminal B:</para>

      <screen>&prompt.root; <userinput>ps aux | grep passwd</userinput></screen>

      <screen>trhodes  5232  0.0  0.2  3420  1608   0  R+    2:10AM   0:00.00 grep passwd
root     5211  0.0  0.2  3620  1724   2  I+    2:09AM   0:00.01 passwd</screen>

      <para>As stated above, the <command>passwd</command> is run
	by a normal user, but is using the effective
	<acronym>UID</acronym> of <username>root</username>.</para>

      <para>The <literal>setgid</literal> permission performs the
	same function as the <literal>setuid</literal> permission;
	except that it alters the group settings.  When an application
	or utility is ran with this setting, it will be granted the
	permissions based on the group that owns the file, not
	the user who started the process.</para>

      <para>To set the <literal>setgid</literal> permission on a
	file, provide the <command>chmod</command> command with a
	leading two (2) as in the following example:</para>

      <screen>&prompt.root; <userinput>chmod 2755 sgidexample.sh</userinput></screen>

      <para>The new setting may be viewed as before, notice the
	<literal>s</literal> is now in the field designated for the
	group permission settings:</para>

      <screen>-rwxr-sr-x   1 trhodes  trhodes    44 Aug 31 01:49 sgidexample.sh</screen>

      <note>
	<para>In these examples, even though the shell script in
	  question is an executable file, it will not run with
	  a different <acronym>EUID</acronym> or effective user ID.
	  This is because shell scripts may not access the
	  &man.setuid.2; system calls.</para>
      </note>

      <para>The first two special permission bits we discussed
	(the <literal>setuid</literal> and <literal>setgid</literal>
	permission bits) may lower system security, by allowing for
	elevated permissions.  There is a third special permission bit
	that can strengthen the security of a system: the
	<literal>sticky bit</literal>.</para>

      <para>The <literal>sticky bit</literal>, when set on a directory,
	allows file deletion only by the file owner.  This
	permission set is useful to prevent file deletion in public
	directories, such as
	<filename class="directory">/tmp</filename>, by users who do
	not own the file.  To utilize this permission, prefix the
	permission with a one (1).  For example:</para>

      <screen>&prompt.root; <userinput>chmod 1777 /tmp</userinput></screen>

      <para>Now, it is possible to see the effect by using the
	<command>ls</command> command:</para>

      <screen>&prompt.root; <userinput>ls -al / | grep tmp</userinput></screen>

      <screen>drwxrwxrwt  10 root  wheel         512 Aug 31 01:49 tmp</screen>

      <para>The <literal>sticky bit</literal> permission is
	distinguishable from the <literal>t</literal> at the very
	end of the set.</para>
    </sect2>
  </sect1>

  <sect1 id="dirstructure">
    <title>Directory Structure</title>
    <indexterm><primary>directory hierarchy</primary></indexterm>

    <para>The FreeBSD directory hierarchy is fundamental to obtaining
      an overall understanding of the system.  The most important
      concept to grasp is that of the root directory,
      <quote>/</quote>.  This directory is the first one mounted at
      boot time and it contains the base system necessary to prepare
      the operating system for multi-user operation.  The root
      directory also contains mount points for other file systems
      that are mounted during the transition to multi-user
      operation.</para>

    <para>A mount point is a directory where additional file systems can
      be grafted onto a parent file system (usually the root file system).
      This is further described in <xref linkend="disk-organization"/>.
      Standard mount points include
      <filename>/usr</filename>, <filename>/var</filename>, <filename>/tmp</filename>,
      <filename>/mnt</filename>, and <filename>/cdrom</filename>.  These
      directories are usually referenced to entries in the file
      <filename>/etc/fstab</filename>.  <filename>/etc/fstab</filename> is
      a table of various file systems and mount points for reference by the
      system.  Most of the file systems in <filename>/etc/fstab</filename>
      are mounted automatically at boot time from the script &man.rc.8;
      unless they contain the <option>noauto</option> option.
      Details can be found in <xref linkend="disks-fstab"/>.</para>

    <para>A complete description of the file system hierarchy is
      available in &man.hier.7;.  For now, a brief overview of the
      most common directories will suffice.</para>

    <para>
      <informaltable frame="none" pgwide="1">
        <tgroup cols="2">
	  <thead>
	    <row>
	      <entry>Directory</entry>
	      <entry>Description</entry>
	    </row>
	  </thead>
	  <tbody valign="top">
            <row>
	      <entry><filename class="directory">/</filename></entry>
	      <entry>Root directory of the file system.</entry>
            </row>

	    <row>
	      <entry><filename class="directory">/bin/</filename></entry>
	      <entry>User utilities fundamental to both single-user
	      and multi-user environments.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/boot/</filename></entry>
	      <entry>Programs and configuration files used during
	      operating system bootstrap.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/boot/defaults/</filename></entry>
	      <entry>Default bootstrapping configuration files; see
	      &man.loader.conf.5;.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/dev/</filename></entry>
	      <entry>Device nodes; see &man.intro.4;.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/etc/</filename></entry>
	      <entry>System configuration files and scripts.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/etc/defaults/</filename></entry>
	      <entry>Default system configuration files; see &man.rc.8;.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/etc/mail/</filename></entry>
	      <entry>Configuration files for mail transport agents such
		as &man.sendmail.8;.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/etc/namedb/</filename></entry>
	      <entry><command>named</command> configuration files; see
	      &man.named.8;.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/etc/periodic/</filename></entry>
	      <entry>Scripts that are run daily, weekly, and monthly,
		via &man.cron.8;; see &man.periodic.8;.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/etc/ppp/</filename></entry>
	      <entry><command>ppp</command> configuration files; see
	      &man.ppp.8;.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/mnt/</filename></entry>
	      <entry>Empty directory commonly used by system administrators as a
		temporary mount point.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/proc/</filename></entry>
	      <entry>Process file system; see &man.procfs.5;,
	      &man.mount.procfs.8;.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/rescue/</filename></entry>
	      <entry>Statically linked programs for emergency recovery; see
		&man.rescue.8;.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/root/</filename></entry>
	      <entry>Home directory for the <username>root</username>
	      account.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/sbin/</filename></entry>
	      <entry>System programs and administration utilities fundamental to
		both single-user and multi-user environments.</entry>
	    </row>


	    <row>
	      <entry><filename class="directory">/tmp/</filename></entry>
	      <entry>Temporary files.  The contents of
		<filename class="directory">/tmp</filename> are usually NOT
		preserved across a system reboot.  A memory-based file system
		is often mounted at
		<filename class="directory">/tmp</filename>.
		This can be automated using the tmpmfs-related variables of
		&man.rc.conf.5; (or with an entry in
		<filename>/etc/fstab</filename>; see &man.mdmfs.8;).</entry>
	    </row>


	    <row>
	      <entry><filename class="directory">/usr/</filename></entry>
	      <entry>The majority of user utilities and applications.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/usr/bin/</filename></entry>
	      <entry>Common utilities, programming tools, and applications.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/usr/include/</filename></entry>
	      <entry>Standard C include files.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/usr/lib/</filename></entry>
	      <entry>Archive libraries.</entry>
	    </row>


	    <row>
	      <entry><filename class="directory">/usr/libdata/</filename></entry>
	      <entry>Miscellaneous utility data files.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/usr/libexec/</filename></entry>
	      <entry>System daemons &amp; system utilities (executed by other
		programs).</entry>
	    </row>

	    <row>
	      <entry><filename
	      class="directory">/usr/local/</filename></entry>

	      <entry>Local executables, libraries, etc.  Also used as
	        the default destination for the FreeBSD ports
	        framework.  Within <filename>/usr/local</filename>,
	        the general layout sketched out by &man.hier.7; for
	        <filename>/usr</filename> should be used.  Exceptions
	        are the man directory, which is directly under
	        <filename>/usr/local</filename> rather than under
	        <filename>/usr/local/share</filename>, and the ports
	        documentation is in
	        <filename>share/doc/<replaceable>port</replaceable></filename>.
	      </entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/usr/obj/</filename></entry>
	      <entry>Architecture-specific target tree produced by building
		the <filename>/usr/src</filename> tree.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/usr/ports/</filename></entry>
	      <entry>The FreeBSD Ports Collection (optional).</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/usr/sbin/</filename></entry>
	      <entry>System daemons &amp; system utilities (executed by users).</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/usr/share/</filename></entry>
	      <entry>Architecture-independent files.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/usr/src/</filename></entry>
	      <entry>BSD and/or local source files.</entry>
	    </row>

	    <row>
	      <entry><filename
	      class="directory">/usr/X11R6/</filename></entry>
	      <entry>X11R6 distribution executables, libraries, etc
	      (optional).</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/var/</filename></entry>
	      <entry>Multi-purpose log, temporary, transient, and spool files.
		A memory-based file system is sometimes mounted at
		<filename class="directory">/var</filename>.
		This can be automated using the varmfs-related variables of
		&man.rc.conf.5; (or with an entry in
		<filename>/etc/fstab</filename>; see &man.mdmfs.8;).</entry>
	    </row>


	    <row>
	      <entry><filename class="directory">/var/log/</filename></entry>
	      <entry>Miscellaneous system log files.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/var/mail/</filename></entry>
	      <entry>User mailbox files.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/var/spool/</filename></entry>
	      <entry>Miscellaneous printer and mail system spooling directories.
	      </entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/var/tmp/</filename></entry>
	      <entry>Temporary files.
		The files are usually preserved across a system reboot,
		unless <filename class="directory">/var</filename>
		is a memory-based file system.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/var/yp/</filename></entry>
	      <entry>NIS maps.</entry>
	    </row>

	  </tbody>
	</tgroup>
      </informaltable>
    </para>

  </sect1>

  <sect1 id="disk-organization">
      <title>Disk Organization</title>

      <para>The smallest unit of organization that FreeBSD uses to find files
	is the filename.  Filenames are case-sensitive, which means that
	<filename>readme.txt</filename> and <filename>README.TXT</filename>
	are two separate files.  FreeBSD does not use the extension
	(<filename>.txt</filename>) of a file to determine whether the file is
	a program, or a document, or some other form of data.</para>

      <para>Files are stored in directories.  A directory may contain no
	files, or it may contain many hundreds of files.  A directory can also
	contain other directories, allowing you to build up a hierarchy of
	directories within one another.  This makes it much easier to organize
	your data.</para>

      <para>Files and directories are referenced by giving the file or
	directory name, followed by a forward slash, <literal>/</literal>,
	followed by any other directory names that are necessary.  If you have
	directory <filename>foo</filename>, which contains directory
	<filename>bar</filename>, which contains the file
	<filename>readme.txt</filename>, then the full name, or
	<firstterm>path</firstterm> to the file is
	<filename>foo/bar/readme.txt</filename>.</para>

      <para>Directories and files are stored in a file system.  Each file system
	contains exactly one directory at the very top level, called the
	<firstterm>root directory</firstterm> for that file system.  This root
	directory can then contain other directories.</para>

      <para>So far this is probably similar to any other operating system you
	may have used.  There are a few differences; for example, &ms-dos; uses
	<literal>\</literal> to separate file and directory names, while &macos;
	uses <literal>:</literal>.</para>

      <para>FreeBSD does not use drive letters, or other drive names in the
	path.  You would not write <filename>c:/foo/bar/readme.txt</filename>
	on FreeBSD.</para>

      <para>Instead, one file system is designated the <firstterm>root
	  file system</firstterm>.  The root file system's root directory is
	referred to as <literal>/</literal>.  Every other file system is then
	<firstterm>mounted</firstterm> under the root file system.  No matter
	how many disks you have on your FreeBSD system, every directory
	appears to be part of the same disk.</para>

      <para>Suppose you have three file systems, called <literal>A</literal>,
	<literal>B</literal>, and <literal>C</literal>.  Each file system has
	one root directory, which contains two other directories, called
	<literal>A1</literal>, <literal>A2</literal> (and likewise
	<literal>B1</literal>, <literal>B2</literal> and
	<literal>C1</literal>, <literal>C2</literal>).</para>

      <para>Call <literal>A</literal> the root file system.  If you used the
	<command>ls</command> command to view the contents of this directory
	you would see two subdirectories, <literal>A1</literal> and
	<literal>A2</literal>.  The directory tree looks like this:</para>

      <mediaobject>
	<imageobject>
	  <imagedata fileref="install/example-dir1" format="EPS"/>
	</imageobject>

	<textobject>
	  <literallayout class="monospaced"> /
 |
 +--- A1
 |
 `--- A2</literallayout>
	</textobject>
      </mediaobject>

      <para>A file system must be mounted on to a directory in another
	file system.  So now suppose that you mount file system
	<literal>B</literal> on to the directory <literal>A1</literal>.  The
	root directory of <literal>B</literal> replaces <literal>A1</literal>,
	and the directories in <literal>B</literal> appear accordingly:</para>

      <mediaobject>
	<imageobject>
	  <imagedata fileref="install/example-dir2" format="EPS"/>
	</imageobject>

	<textobject>
	  <literallayout class="monospaced"> /
 |
 +--- A1
 |     |
 |     +--- B1
 |     |
 |     `--- B2
 |
 `--- A2</literallayout>
	</textobject>
      </mediaobject>

      <para>Any files that are in the <literal>B1</literal> or
	<literal>B2</literal> directories can be reached with the path
	<filename>/A1/B1</filename> or <filename>/A1/B2</filename> as
	necessary.  Any files that were in <filename>/A1</filename> have been
	temporarily hidden.  They will reappear if <literal>B</literal> is
	<firstterm>unmounted</firstterm> from A.</para>

      <para>If <literal>B</literal> had been mounted on <literal>A2</literal>
	then the diagram would look like this:</para>

      <mediaobject>
	<imageobject>
	  <imagedata fileref="install/example-dir3" format="EPS"/>
	</imageobject>

	<textobject>
	  <literallayout class="monospaced"> /
 |
 +--- A1
 |
 `--- A2
       |
       +--- B1
       |
       `--- B2</literallayout>
	</textobject>
      </mediaobject>

      <para>and the paths would be <filename>/A2/B1</filename> and
	<filename>/A2/B2</filename> respectively.</para>

      <para>File systems can be mounted on top of one another.  Continuing the
	last example, the <literal>C</literal> file system could be mounted on
	top of the <literal>B1</literal> directory in the <literal>B</literal>
	file system, leading to this arrangement:</para>

      <mediaobject>
	<imageobject>
	  <imagedata fileref="install/example-dir4" format="EPS"/>
	</imageobject>

	<textobject>
	  <literallayout class="monospaced"> /
 |
 +--- A1
 |
 `--- A2
       |
       +--- B1
       |     |
       |     +--- C1
       |     |
       |     `--- C2
       |
       `--- B2</literallayout>
	</textobject>
      </mediaobject>

      <para>Or <literal>C</literal> could be mounted directly on to the
	<literal>A</literal> file system, under the <literal>A1</literal>
	directory:</para>

      <mediaobject>
	<imageobject>
	  <imagedata fileref="install/example-dir5" format="EPS"/>
	</imageobject>

	<textobject>
	  <literallayout class="monospaced"> /
 |
 +--- A1
 |     |
 |     +--- C1
 |     |
 |     `--- C2
 |
 `--- A2
       |
       +--- B1
       |
       `--- B2</literallayout>
	</textobject>
      </mediaobject>

      <para>If you are familiar with &ms-dos;, this is similar, although not
	identical, to the <command>join</command> command.</para>

      <para>This is not normally something you need to concern yourself with.
	Typically you create file systems when installing FreeBSD and decide
	where to mount them, and then never change them unless you add a new
	disk.</para>

      <para>It is entirely possible to have one large root file system, and not
	need to create any others.  There are some drawbacks to this approach,
	and one advantage.</para>

      <itemizedlist>
	<title>Benefits of Multiple File Systems</title>

	<listitem>
	  <para>Different file systems can have different <firstterm>mount
	    options</firstterm>.  For example, with careful planning, the
	    root file system can be mounted read-only, making it impossible for
	    you to inadvertently delete or edit a critical file.  Separating
	    user-writable file systems, such as <filename>/home</filename>,
	    from other file systems also allows them to be mounted
	    <firstterm>nosuid</firstterm>; this option prevents the
	    <firstterm>suid</firstterm>/<firstterm>guid</firstterm> bits on
	    executables stored on the file system from taking effect, possibly
	    improving security.</para>
	</listitem>

	<listitem>
	  <para>FreeBSD automatically optimizes the layout of files on a
	    file system, depending on how the file system is being used.  So a
	    file system that contains many small files that are written
	    frequently will have a different optimization to one that contains
	    fewer, larger files.  By having one big file system this
	    optimization breaks down.</para>
	</listitem>

	<listitem>
	  <para>FreeBSD's file systems are very robust should you lose power.
	    However, a power loss at a critical point could still damage the
	    structure of the file system.  By splitting your data over multiple
	    file systems it is more likely that the system will still come up,
	    making it easier for you to restore from backup as necessary.</para>
	</listitem>
      </itemizedlist>

      <itemizedlist>
	<title>Benefit of a Single File System</title>

	<listitem>
	  <para>File systems are a fixed size.  If you create a file system when
	    you install FreeBSD and give it a specific size, you may later
	    discover that you need to make the partition bigger.  This is not
	    easily accomplished without backing up, recreating the file system
	    with the new size, and then restoring the backed up data.</para>

	  <important>
	    <para>FreeBSD features the &man.growfs.8;
	      command, which makes it possible to increase the size of
	      file system on the fly, removing this limitation.</para>
	  </important>
	</listitem>
      </itemizedlist>

      <para>File systems are contained in partitions.  This does not have the
	same meaning as the common usage of the term partition (for example, &ms-dos;
	partition), because of &os;'s &unix; heritage.  Each partition is
	identified by a letter from <literal>a</literal> through to
	<literal>h</literal>.  Each partition can contain only one file system,
	which means that file systems are often described by either their
	typical mount point in the file system hierarchy, or the letter of the
	partition they are contained in.</para>

      <para>FreeBSD also uses disk space for <firstterm>swap
	  space</firstterm>.  Swap space provides FreeBSD with
	<firstterm>virtual memory</firstterm>.  This allows your computer to
	behave as though it has much more memory than it actually does.  When
	FreeBSD runs out of memory it moves some of the data that is not
	currently being used to the swap space, and moves it back in (moving
	something else out) when it needs it.</para>

      <para>Some partitions have certain conventions associated with
	them.</para>

      <informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	  <colspec colwidth="1*"/>
	  <colspec colwidth="5*"/>

	  <thead>
	    <row>
	      <entry>Partition</entry>

	      <entry>Convention</entry>
	    </row>
	  </thead>

	  <tbody valign="top">
	    <row>
	      <entry><literal>a</literal></entry>

	      <entry>Normally contains the root file system</entry>
	    </row>

	    <row>
	      <entry><literal>b</literal></entry>

	      <entry>Normally contains swap space</entry>
	    </row>

	    <row>
	      <entry><literal>c</literal></entry>

	      <entry>Normally the same size as the enclosing slice.  This
		allows utilities that need to work on the entire slice (for
		example, a bad block scanner) to work on the
		<literal>c</literal> partition.  You would not normally create
		a file system on this partition.</entry>
	    </row>

	    <row>
	      <entry><literal>d</literal></entry>

	      <entry>Partition <literal>d</literal> used to have a special
		meaning associated with it, although that is now gone and
		<literal>d</literal> may work as any normal partition.</entry>
	    </row>
	  </tbody>
	</tgroup>
      </informaltable>

      <para>Each partition-that-contains-a-file-system is stored in what
	FreeBSD calls a <firstterm>slice</firstterm>.  Slice is FreeBSD's term
	for what the common call partitions, and again, this is because of
	FreeBSD's &unix; background.  Slices are numbered, starting at 1,
	through to 4.</para>

	<indexterm><primary>slices</primary></indexterm>
	<indexterm><primary>partitions</primary></indexterm>
	<indexterm><primary>dangerously dedicated</primary></indexterm>

      <para>Slice numbers follow
	the device name, prefixed with an <literal>s</literal>,
	starting at 1.  So <quote>da0<emphasis>s1</emphasis></quote>
	is the first slice on the first SCSI drive.  There can only be
	four physical slices on a disk, but you can have logical
	slices inside physical slices of the appropriate type.  These
	extended slices are numbered starting at 5, so
	<quote>ad0<emphasis>s5</emphasis></quote> is the first
	extended slice on the first IDE disk.  These devices are used by file
	systems that expect to occupy a slice.</para>

      <para>Slices, <quote>dangerously dedicated</quote> physical
	drives, and other drives contain
	<firstterm>partitions</firstterm>, which are represented as
	letters from <literal>a</literal> to <literal>h</literal>.
	This letter is appended to the device name, so
	<quote>da0<emphasis>a</emphasis></quote> is the a partition on
	the first da drive, which is <quote>dangerously dedicated</quote>.
	<quote>ad1s3<emphasis>e</emphasis></quote> is the fifth partition
	in the third slice of the second IDE disk drive.</para>

      <para>Finally, each disk on the system is identified.  A disk name
	starts with a code that indicates the type of disk, and then a number,
	indicating which disk it is.  Unlike slices, disk numbering starts at
	0.  Common codes that you will see are listed in
	<xref linkend="basics-dev-codes"/>.</para>

      <para>When referring to a partition FreeBSD requires that you also name
	the slice and disk that contains the partition, and when referring to
	a slice you must also refer to the disk name.
	Thus, you refer to a partition by listing
	the disk name, <literal>s</literal>, the slice number, and then the
	partition letter.  Examples are shown in
	<xref linkend="basics-disk-slice-part"/>.</para>

      <para><xref linkend="basics-concept-disk-model"/> shows a conceptual
	model of the disk layout that should help make things clearer.</para>

      <para>In order to install FreeBSD you must first configure the disk
	slices, then create partitions within the slice you will use for
	FreeBSD, and then create a file system (or swap space) in each
	partition, and decide where that file system will be mounted.</para>

      <table frame="none" pgwide="1" id="basics-dev-codes">
	<title>Disk Device Codes</title>

	<tgroup cols="2">
          <colspec colwidth="1*"/>
          <colspec colwidth="5*"/>

	  <thead>
	    <row>
	      <entry>Code</entry>

	      <entry>Meaning</entry>
	    </row>
	  </thead>

	  <tbody>
	    <row>
	      <entry><devicename>ad</devicename></entry>

	      <entry>ATAPI (IDE) disk</entry>
	    </row>

	    <row>
	      <entry><devicename>da</devicename></entry>

	      <entry>SCSI direct access disk</entry>
	    </row>

	    <row>
	      <entry><devicename>acd</devicename></entry>

	      <entry>ATAPI (IDE) CDROM</entry>
	    </row>

	    <row>
	      <entry><devicename>cd</devicename></entry>

	      <entry>SCSI CDROM</entry>
	    </row>

	    <row>
	      <entry><devicename>fd</devicename></entry>

	      <entry>Floppy disk</entry>
	    </row>
	  </tbody>
	</tgroup>
      </table>

      <example id="basics-disk-slice-part">
	<title>Sample Disk, Slice, and Partition Names</title>

	<informaltable frame="none" pgwide="1">
	  <tgroup cols="2">
            <colspec colwidth="1*"/>
            <colspec colwidth="5*"/>

	    <thead>
	      <row>
		<entry>Name</entry>

		<entry>Meaning</entry>
	      </row>
	    </thead>

	    <tbody>
	      <row>
		<entry><literal>ad0s1a</literal></entry>

		<entry>The first partition (<literal>a</literal>) on the first
		  slice (<literal>s1</literal>) on the first IDE disk
		  (<literal>ad0</literal>).</entry>
	      </row>

	      <row>
		<entry><literal>da1s2e</literal></entry>

		<entry>The fifth partition (<literal>e</literal>) on the
		  second slice (<literal>s2</literal>) on the second SCSI disk
		  (<literal>da1</literal>).</entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable>
      </example>

      <example id="basics-concept-disk-model">
	<title>Conceptual Model of a Disk</title>

	<para>This diagram shows FreeBSD's view of the first IDE disk attached
	  to the system.  Assume that the disk is 4&nbsp;GB in size, and contains
	  two 2&nbsp;GB slices (&ms-dos; partitions).  The first slice contains a &ms-dos;
	  disk, <devicename>C:</devicename>, and the second slice contains a
	  FreeBSD installation.  This example FreeBSD installation has three
	  data partitions, and a swap partition.</para>

	<para>The three partitions will each hold a file system.  Partition
	  <literal>a</literal> will be used for the root file system,
	  <literal>e</literal> for the <filename>/var</filename> directory
	  hierarchy, and <literal>f</literal> for the
	  <filename>/usr</filename> directory hierarchy.</para>

        <mediaobject>
          <imageobject>
            <imagedata fileref="install/disk-layout" format="EPS"/>
          </imageobject>

          <textobject>
	    <literallayout class="monospaced">.-----------------.  --.
|                 |    |
|  DOS / Windows  |    |
:                 :     &gt;  First slice, ad0s1
:                 :    |
|                 |    |
:=================:  ==:                               --.
|                 |    |  Partition a, mounted as /      |
|                 |     &gt; referred to as ad0s2a          |
|                 |    |                                 |
:-----------------:  ==:                                 |
|                 |    |  Partition b, used as swap      |
|                 |     &gt; referred to as ad0s2b          |
|                 |    |                                 |
:-----------------:  ==:                                 |  Partition c, no
|                 |    |  Partition e, used as /var       &gt; file system, all
|                 |     &gt; referred to as ad0s2e          |  of FreeBSD slice,
|                 |    |                                 |  ad0s2c
:-----------------:  ==:                                 |
|                 |    |                                 |
:                 :    |  Partition f, used as /usr      |
:                 :     &gt; referred to as ad0s2f          |
:                 :    |                                 |
|                 |    |                                 |
|                 |  --'                                 |
`-----------------'                                    --'</literallayout>
          </textobject>
        </mediaobject>
      </example>
  </sect1>



  <sect1 id="mount-unmount">
    <title>Mounting and Unmounting File Systems</title>

    <para>The file system is best visualized as a tree,
      rooted, as it were, at <filename>/</filename>.
      <filename>/dev</filename>, <filename>/usr</filename>, and the
      other directories in the root directory are branches, which may
      have their own branches, such as
      <filename>/usr/local</filename>, and so on.</para>

    <indexterm><primary>root file system</primary></indexterm>
    <para>There are various reasons to house some of these
      directories on separate file systems.  <filename>/var</filename>
      contains the directories <filename>log/</filename>,
      <filename>spool/</filename>,
      and various types of temporary files, and
      as such, may get filled up.  Filling up the root file system
      is not a good idea, so splitting <filename>/var</filename> from
      <filename>/</filename> is often favorable.</para>

    <para>Another common reason to contain certain directory trees on
      other file systems is if they are to be housed on separate
      physical disks, or are separate virtual disks, such as <link
	linkend="network-nfs">Network File System</link> mounts, or CDROM
      drives.</para>

    <sect2 id="disks-fstab">
      <title>The <filename>fstab</filename> File</title>
      <indexterm>
	<primary>file systems</primary>
	<secondary>mounted with fstab</secondary>
      </indexterm>

      <para>During the <link linkend="boot">boot process</link>,
	file systems listed in <filename>/etc/fstab</filename> are
	automatically mounted (unless they are listed with the
	<option>noauto</option> option).</para>

      <para>The <filename>/etc/fstab</filename> file contains a list
	of lines of the following format:</para>

      <programlisting><replaceable>device</replaceable>       <replaceable>/mount-point</replaceable> <replaceable>fstype</replaceable>     <replaceable>options</replaceable>      <replaceable>dumpfreq</replaceable>     <replaceable>passno</replaceable></programlisting>

      <variablelist>
	<varlistentry>
	  <term><literal>device</literal></term>
	  <listitem>
	    <para>A device name (which should exist), as explained in
	      <xref linkend="disks-naming"/>.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><literal>mount-point</literal></term>

	  <listitem><para>A directory (which should exist), on which
	      to mount the file system.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><literal>fstype</literal></term>

	  <listitem><para>The file system type to pass to
		&man.mount.8;.  The default FreeBSD file system is
	      <literal>ufs</literal>.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><literal>options</literal></term>

	  <listitem><para>Either <option>rw</option> for read-write
	      file systems, or <option>ro</option> for read-only
	      file systems, followed by any other options that may be
	      needed.  A common option is <option>noauto</option> for
	      file systems not normally mounted during the boot sequence.
	      Other options are listed in the &man.mount.8; manual page.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><literal>dumpfreq</literal></term>

         <listitem><para>This is used by &man.dump.8; to determine which
             file systems require dumping.  If the field is missing,
             a value of zero is assumed.</para>
         </listitem>
       </varlistentry>

       <varlistentry>
         <term><literal>passno</literal></term>

         <listitem>
           <para>This determines the order in which file systems should
           be checked.  File systems that should be skipped should have
           their <literal>passno</literal> set to zero.  The root
           file system (which needs to be checked before everything
           else) should have its <literal>passno</literal> set to
           one, and other file systems' <literal>passno</literal>
           should be set to values greater than one.  If more than one
           file systems have the same <literal>passno</literal> then
           &man.fsck.8; will attempt to check file systems in parallel
           if possible.</para>
         </listitem>
	</varlistentry>
      </variablelist>

      <para>Consult the &man.fstab.5; manual page for more information
	on the format of the <filename>/etc/fstab</filename> file and
	the options it contains.</para>
    </sect2>

    <sect2 id="disks-mount">
      <title>The <command>mount</command> Command</title>
      <indexterm>
	<primary>file systems</primary>
	<secondary>mounting</secondary>
      </indexterm>

      <para>The &man.mount.8; command is what is ultimately used to
	mount file systems.</para>

      <para>In its most basic form, you use:</para>

      <informalexample>
	<screen>&prompt.root; <userinput>mount <replaceable>device</replaceable> <replaceable>mountpoint</replaceable></userinput></screen>
      </informalexample>

      <para>There are plenty of options, as mentioned in the
	  &man.mount.8; manual page, but the most common are:</para>

      <variablelist>
	<title>Mount Options</title>

	<varlistentry>
	  <term><option>-a</option></term>

	  <listitem>
	    <para>Mount all the file systems listed in
	      <filename>/etc/fstab</filename>. Except those
	      marked as <quote>noauto</quote>, excluded by the
	      <option>-t</option> flag, or those that are already
	      mounted.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>-d</option></term>

	  <listitem>
	    <para>Do everything except for the actual mount system call.
	      This option is useful in conjunction with the
	      <option>-v</option> flag to determine what
	      &man.mount.8; is actually trying to do.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>-f</option></term>

	  <listitem>
	    <para>Force the mount of an unclean file system
	      (dangerous), or forces the revocation of write access
	      when downgrading a file system's mount status from
	      read-write to read-only.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
          <term><option>-r</option></term>

	  <listitem>
	    <para>Mount the file system read-only.  This is identical
	      to using the <option>ro</option>
	      argument to the
	      <option>-o</option> option.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>-t</option>
	    <replaceable>fstype</replaceable></term>

	  <listitem>
	    <para>Mount the given file system as the given file system
	      type, or mount only file systems of the given type, if
	      given the <option>-a</option> option.</para>

	    <para><quote>ufs</quote> is the default file system
	      type.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>-u</option></term>

	  <listitem>
	    <para>Update mount options on the file system.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>-v</option></term>

	  <listitem>
	    <para>Be verbose.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>-w</option></term>

	  <listitem>
	    <para>Mount the file system read-write.</para>
	  </listitem>
	</varlistentry>
      </variablelist>

      <para>The <option>-o</option> option takes a comma-separated list of
	the options, including the following:</para>

      <variablelist>
	<varlistentry>
	  <term>noexec</term>

	  <listitem>
              <para>Do not allow execution of binaries on this
	      file system.  This is also a useful security option.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>nosuid</term>

	  <listitem>
	    <para>Do not interpret setuid or setgid flags on the
	      file system.  This is also a useful security option.</para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </sect2>

    <sect2 id="disks-umount">
      <title>The <command>umount</command> Command</title>
      <indexterm>
	<primary>file systems</primary>
	<secondary>unmounting</secondary>
      </indexterm>

      <para>The &man.umount.8; command takes, as a parameter, one of a
	mountpoint, a device name, or the <option>-a</option> or
	<option>-A</option> option.</para>

      <para>All forms take <option>-f</option> to force unmounting,
        and <option>-v</option> for verbosity.  Be warned that
        <option>-f</option> is not generally a good idea.  Forcibly
        unmounting file systems might crash the computer or damage data
        on the file system.</para>

      <para><option>-a</option> and <option>-A</option> are used to
	unmount all mounted file systems, possibly modified by the
	file system types listed after <option>-t</option>.
	<option>-A</option>, however, does not attempt to unmount the
	root file system.</para>
    </sect2>
  </sect1>

  <sect1 id="basics-processes">
    <title>Processes</title>

    <para>FreeBSD is a multi-tasking operating system.  This means that it
      seems as though more than one program is running at once.  Each program
      running at any one time is called a <firstterm>process</firstterm>.
      Every command you run will start at least one new process, and there are
      a number of system processes that run all the time, keeping the system
      functional.</para>

    <para>Each process is uniquely identified by a number called a
      <firstterm>process ID</firstterm>, or <firstterm>PID</firstterm>, and,
      like files, each process also has one owner and group.  The owner and
      group information is used to determine what files and devices the
      process can open, using the file permissions discussed earlier.  Most
      processes also have a parent process.  The parent process is the process
      that started them.  For example, if you are typing commands to the shell
      then the shell is a process, and any commands you run are also
      processes.  Each process you run in this way will have your shell as its
      parent process.  The exception to this is a special process called
      &man.init.8;.  <command>init</command> is always the first
      process, so its PID is always 1.  <command>init</command> is started
      automatically by the kernel when FreeBSD starts.</para>

    <para>Two commands are particularly useful to see the processes on the
      system, &man.ps.1; and &man.top.1;.  The <command>ps</command> command is used to
      show a static list of the currently running processes, and can show
      their PID, how much memory they are using, the command line they were
      started with, and so on.  The <command>top</command> command displays all the
      running processes, and updates the display every few seconds, so that
      you can interactively see what your computer is doing.</para>

    <para>By default, <command>ps</command> only shows you the commands that are running
      and are owned by you.  For example:</para>

    <screen>&prompt.user; <userinput>ps</userinput>
  PID  TT  STAT      TIME COMMAND
  298  p0  Ss     0:01.10 tcsh
 7078  p0  S      2:40.88 xemacs mdoc.xsl (xemacs-21.1.14)
37393  p0  I      0:03.11 xemacs freebsd.dsl (xemacs-21.1.14)
48630  p0  S      2:50.89 /usr/local/lib/netscape-linux/navigator-linux-4.77.bi
48730  p0  IW     0:00.00 (dns helper) (navigator-linux-)
72210  p0  R+     0:00.00 ps
  390  p1  Is     0:01.14 tcsh
 7059  p2  Is+    1:36.18 /usr/local/bin/mutt -y
 6688  p3  IWs    0:00.00 tcsh
10735  p4  IWs    0:00.00 tcsh
20256  p5  IWs    0:00.00 tcsh
  262  v0  IWs    0:00.00 -tcsh (tcsh)
  270  v0  IW+    0:00.00 /bin/sh /usr/X11R6/bin/startx -- -bpp 16
  280  v0  IW+    0:00.00 xinit /home/nik/.xinitrc -- -bpp 16
  284  v0  IW     0:00.00 /bin/sh /home/nik/.xinitrc
  285  v0  S      0:38.45 /usr/X11R6/bin/sawfish</screen>

    <para>As you can see in this example, the output from &man.ps.1; is
      organized into a number of columns.  <literal>PID</literal> is the
      process ID discussed earlier.  PIDs are assigned starting from 1, go up
      to 99999, and wrap around back to the beginning when you run out
      (a PID is not reassigned if it is already in use).
      The <literal>TT</literal> column shows the tty the program is running on, and can
      safely be ignored for the moment.  <literal>STAT</literal> shows the
      program's state, and again, can be safely ignored.
      <literal>TIME</literal> is the amount of time the program has been
      running on the CPU&mdash;this is usually not the elapsed time since
      you started the program, as most programs spend a lot of time waiting
      for things to happen before they need to spend time on the CPU.
      Finally, <literal>COMMAND</literal> is the command line that was used to
      run the program.</para>

    <para>&man.ps.1; supports a number of different options to change the
      information that is displayed.  One of the most useful sets is
      <literal>auxww</literal>.  <option>a</option> displays information
      about all the running processes, not just your own.  <option>u</option>
      displays the username of the process' owner, as well as memory usage.
      <option>x</option> displays information about daemon processes, and
      <option>ww</option> causes &man.ps.1; to display the full command line
      for each process,
      rather than truncating it once it gets too long to fit on the
      screen.</para>

    <para>The output from &man.top.1; is similar.  A sample session looks like
      this:</para>

    <screen>&prompt.user; <userinput>top</userinput>
last pid: 72257;  load averages:  0.13,  0.09,  0.03    up 0+13:38:33  22:39:10
47 processes:  1 running, 46 sleeping
CPU states: 12.6% user,  0.0% nice,  7.8% system,  0.0% interrupt, 79.7% idle
Mem: 36M Active, 5256K Inact, 13M Wired, 6312K Cache, 15M Buf, 408K Free
Swap: 256M Total, 38M Used, 217M Free, 15% Inuse

  PID USERNAME PRI NICE  SIZE    RES STATE    TIME   WCPU    CPU COMMAND
72257 nik       28   0  1960K  1044K RUN      0:00 14.86%  1.42% top
 7078 nik        2   0 15280K 10960K select   2:54  0.88%  0.88% xemacs-21.1.14
  281 nik        2   0 18636K  7112K select   5:36  0.73%  0.73% XF86_SVGA
  296 nik        2   0  3240K  1644K select   0:12  0.05%  0.05% xterm
48630 nik        2   0 29816K  9148K select   3:18  0.00%  0.00% navigator-linu
  175 root       2   0   924K   252K select   1:41  0.00%  0.00% syslogd
 7059 nik        2   0  7260K  4644K poll     1:38  0.00%  0.00% mutt
...</screen>

    <para>The output is split into two sections.  The header (the first five
      lines) shows the PID of the last process to run, the system load averages
      (which are a measure of how busy the system is), the system uptime (time
      since the last reboot) and the current time.  The other figures in the
      header relate to how many processes are running (47 in this case), how
      much memory and swap space has been taken up, and how much time the
      system is spending in different CPU states.</para>

    <para>Below that are a series of columns containing similar information
      to the output from &man.ps.1;.  As before you can see the PID, the
      username, the amount of CPU time taken, and the command that was run.
      &man.top.1; also defaults to showing you the amount of memory space
      taken by the process.  This is split into two columns, one for total
      size, and one for resident size&mdash;total size is how much memory the
      application has needed, and the resident size is how much it is actually
      using at the moment.  In this example you can see that <application>&netscape;</application> has
      required almost 30&nbsp;MB of RAM, but is currently only using 9&nbsp;MB.</para>

    <para>&man.top.1; automatically updates this display every two seconds;
      this can be changed with the <option>s</option> option.</para>
  </sect1>

  <sect1 id="basics-daemons">
    <title>Daemons, Signals, and Killing Processes</title>

    <para>When you run an editor it is easy to control the editor, tell it to
      load files, and so on.  You can do this because the editor provides
      facilities to do so, and because the editor is attached to a
      <firstterm>terminal</firstterm>.  Some programs are not designed to be
      run with continuous user input, and so they disconnect from the terminal
      at the first opportunity.  For example, a web server spends all day
      responding to web requests, it normally does not need any input from
      you.  Programs that transport email from site to site are another
      example of this class of application.</para>

    <para>We call these programs <firstterm>daemons</firstterm>.  Daemons were
      characters in Greek mythology: neither good or evil, they were little
      attendant spirits that, by and large, did useful things for mankind,
      much like the web servers and mail servers of today do useful things.
      This is why the BSD mascot has, for a long time, been the
      cheerful-looking daemon with sneakers and a pitchfork.</para>

    <para>There is a convention to name programs that normally run as daemons
      with a trailing <quote>d</quote>. <application>BIND</application> is the
      Berkeley Internet Name Domain, but the actual program that executes is called
      <command>named</command>; the <application>Apache</application> web
      server program is called <command>httpd</command>; the line printer
      spooling daemon is <command>lpd</command> and so on.  This is a
      convention, not a hard and fast rule; for example, the main mail daemon
      for the <application>Sendmail</application> application is called
      <command>sendmail</command>, and not <command>maild</command>, as you
      might imagine.</para>

    <para>Sometimes you will need to communicate with a daemon process.
      One way to do so is to send it (or any other running process),
      what is known as a <firstterm>signal</firstterm>.
      There are a number of different signals that you can
      send&mdash;some of them have a specific meaning, others are interpreted
      by the application, and the application's documentation will tell you
      how that application interprets signals.  You can only send a signal to
      a process that you own.  If you send a signal to someone else's
      process with &man.kill.1; or &man.kill.2;, permission will be denied.
      The exception to this is the
      <username>root</username> user, who can send signals to everyone's
      processes.</para>

    <para>FreeBSD will also send applications signals in some cases.  If an
      application is badly written, and tries to access memory that it is not
      supposed to, FreeBSD sends the process the <firstterm>Segmentation
	Violation</firstterm> signal (<literal>SIGSEGV</literal>).  If an
      application has used the &man.alarm.3; system call to be alerted after a
      period of time has elapsed then it will be sent the Alarm signal
      (<literal>SIGALRM</literal>), and so on.</para>

    <para>Two signals can be used to stop a process,
      <literal>SIGTERM</literal> and <literal>SIGKILL</literal>.
      <literal>SIGTERM</literal> is the polite way to kill a process; the
      process can <emphasis>catch</emphasis> the signal, realize that you want
      it to shut down, close any log files it may have open, and generally
      finish whatever it is doing at the time before shutting down.  In some
      cases a process may even ignore <literal>SIGTERM</literal> if it is in
      the middle of some task that can not be interrupted.</para>

    <para><literal>SIGKILL</literal> can not be ignored by a process.  This is
      the <quote>I do not care what you are doing, stop right now</quote>
      signal.  If you send <literal>SIGKILL</literal> to a process then
      FreeBSD will stop that process there and then<footnote>
	<para>Not quite true&mdash;there are a few things that can not be
	  interrupted.  For example, if the process is trying to read from a
	  file that is on another computer on the network, and the other
	  computer has gone away for some reason (been turned off, or the
	  network has a fault), then the process is said to be
	  <quote>uninterruptible</quote>.  Eventually the process will time
	  out, typically after two minutes.  As soon as this time out occurs
	  the process will be killed.</para>
      </footnote>.</para>

    <para>The other signals you might want to use are
      <literal>SIGHUP</literal>, <literal>SIGUSR1</literal>, and
      <literal>SIGUSR2</literal>.  These are general purpose signals, and
      different applications will do different things when they are
      sent.</para>

    <para>Suppose that you have changed your web server's configuration
      file&mdash;you would like to tell the web server to re-read its
      configuration.  You could stop and restart <command>httpd</command>, but
      this would result in a brief outage period on your web server, which may
      be undesirable.  Most daemons are written to respond to the
      <literal>SIGHUP</literal> signal by re-reading their configuration
      file.  So instead of killing and restarting <command>httpd</command> you
      would send it the <literal>SIGHUP</literal> signal.  Because there is no
      standard way to respond to these signals, different daemons will have
      different behavior, so be sure and read the documentation for the
      daemon in question.</para>

    <para>Signals are sent using the &man.kill.1; command, as this example
      shows.</para>

    <procedure>
      <title>Sending a Signal to a Process</title>

      <para>This example shows how to send a signal to &man.inetd.8;.  The
	  <command>inetd</command> configuration file is
	<filename>/etc/inetd.conf</filename>, and <command>inetd</command> will re-read
	this configuration file when it is sent
	<literal>SIGHUP</literal>.</para>

      <step>
	<para>Find the process ID of the process you want to send the signal
	  to.  Do this using &man.ps.1; and &man.grep.1;.  The &man.grep.1;
	  command is used to search through output, looking for the string you
	  specify.  This command is run as a normal user, and &man.inetd.8; is
	  run as <username>root</username>, so the <option>ax</option> options
	  must be given to &man.ps.1;.</para>

	<screen>&prompt.user; <userinput>ps -ax | grep inetd</userinput>
  198  ??  IWs    0:00.00 inetd -wW</screen>

	<para>So the &man.inetd.8; PID is 198.  In some cases the
	  <literal>grep inetd</literal> command might also appear in this
	  output.  This is because of the way &man.ps.1; has to find the list
	  of running processes.</para>
      </step>

      <step>
	<para>Use &man.kill.1; to send the signal.  Because &man.inetd.8; is
	  being run by <username>root</username> you must use &man.su.1; to
	  become <username>root</username> first.</para>

	<screen>&prompt.user; <userinput>su</userinput>
<prompt>Password:</prompt>
&prompt.root; <userinput>/bin/kill -s HUP 198</userinput></screen>

	<para>In common with most &unix; commands, &man.kill.1; will not print any
	  output if it is successful.  If you send a signal to a
	  process that you do not own then you will see <errorname>kill:
	    <replaceable>PID</replaceable>: Operation not
	    permitted</errorname>.  If you mistype the PID you will either
	  send the signal to the wrong process, which could be bad, or, if
	  you are lucky, you will have sent the signal to a PID that is not
	  currently in use, and you will see <errorname>kill:
	    <replaceable>PID</replaceable>: No such process</errorname>.</para>

	<note>
	  <title>Why Use <command>/bin/kill</command>?</title>

	  <para>Many shells provide the <command>kill</command> command as a
	    built in command; that is, the shell will send the signal
	    directly, rather than running <filename>/bin/kill</filename>.
	    This can be very useful, but different shells have a different
	    syntax for specifying the name of the signal to send.  Rather than
	    try to learn all of them, it can be simpler just to use the
	    <command>/bin/kill <replaceable>...</replaceable></command>
	    command directly.</para>
	</note>
      </step>
    </procedure>

    <para>Sending other signals is very similar, just substitute
      <literal>TERM</literal> or <literal>KILL</literal> in the command line
      as necessary.</para>

    <important>
      <para>Killing random process on the system can be a bad idea.  In
	particular, &man.init.8;, process ID 1, is very special.  Running
	<command>/bin/kill -s KILL 1</command> is a quick way to shutdown your
	system.  <emphasis>Always</emphasis> double check the arguments you
	run &man.kill.1; with <emphasis>before</emphasis> you press
	<keycap>Return</keycap>.</para>
    </important>
  </sect1>

  <sect1 id="shells">
    <title>Shells</title>
    <indexterm><primary>shells</primary></indexterm>
    <indexterm><primary>command line</primary></indexterm>

    <para>In FreeBSD, a lot of everyday work is done in a command line
      interface called a shell.  A shell's main job is to take commands
      from the input channel and execute them.  A lot of shells also have
      built in functions to help with everyday tasks such as file management,
      file globbing, command line editing, command macros, and environment
      variables.  FreeBSD comes with a set of shells, such as
      <command>sh</command>, the Bourne Shell, and <command>tcsh</command>,
      the improved C-shell.  Many other shells are available
      from the FreeBSD Ports Collection, such as
      <command>zsh</command> and <command>bash</command>.</para>

    <para>Which shell do you use?  It is really a matter of taste.  If you
      are a C programmer you might feel more comfortable with a C-like shell
      such as <command>tcsh</command>.  If you have come from Linux or are new
      to a &unix; command line interface you might try <command>bash</command>.
      The point is that each
      shell has unique properties that may or may not work with your
      preferred working environment, and that you have a choice of what
      shell to use.</para>

    <para>One common feature in a shell is filename completion.  Given
      the typing of the first few letters of a command or filename, you
      can usually have the shell automatically complete the rest of the
      command or filename by hitting the <keycap>Tab</keycap> key on the keyboard.  Here is
      an example.  Suppose you have two files called
      <filename>foobar</filename> and <filename>foo.bar</filename>.  You
      want to delete <filename>foo.bar</filename>.  So what you would type
      on the keyboard is: <command>rm fo[<keycap>Tab</keycap>].[<keycap>Tab</keycap>]</command>.</para>

    <para>The shell would print out <command>rm
      foo[BEEP].bar</command>.</para>

    <para>The [BEEP] is the console bell, which is the shell telling me it
      was unable to totally complete the filename because there is more
      than one match.  Both <filename>foobar</filename> and
      <filename>foo.bar</filename> start with <literal>fo</literal>, but
      it was able to complete to <literal>foo</literal>.  If you type in
      <literal>.</literal>, then hit <keycap>Tab</keycap> again, the shell would be able to
      fill in the rest of the filename for you.</para>
    <indexterm><primary>environment variables</primary></indexterm>

    <para>Another feature of the shell is the use of environment variables.
      Environment variables are a variable/key pair stored in the shell's
      environment space.  This space can be read by any program invoked by
      the shell, and thus contains a lot of program configuration.  Here
      is a list of common environment variables and what they mean:</para>
    <indexterm><primary>environment variables</primary></indexterm>

    <informaltable frame="none" pgwide="1">
      <tgroup cols="2">
	<thead>
	  <row>
	    <entry>Variable</entry>
	    <entry>Description</entry>
	  </row>
	</thead>

	<tbody>
	  <row>
	    <entry><envar>USER</envar></entry>
	    <entry>Current logged in user's name.</entry>
	  </row>

	  <row>
	    <entry><envar>PATH</envar></entry>
	    <entry>Colon-separated list of directories to search for
	      binaries.</entry>
	  </row>

	  <row>
	    <entry><envar>DISPLAY</envar></entry>
	    <entry>Network name of the X11 display to connect to, if
	      available.</entry>
	  </row>

	  <row>
	    <entry><envar>SHELL</envar></entry>
	    <entry>The current shell.</entry>
	  </row>

	  <row>
	    <entry><envar>TERM</envar></entry>
	    <entry>The name of the user's type of terminal.  Used to determine the
	      capabilities of the terminal.</entry>
	  </row>

	  <row>
	    <entry><envar>TERMCAP</envar></entry>
	    <entry>Database entry of the terminal escape codes to perform
	      various terminal functions.</entry>
	  </row>

	  <row>
	    <entry><envar>OSTYPE</envar></entry>
	    <entry>Type of operating system.  e.g., FreeBSD.</entry>
	  </row>

	  <row>
	    <entry><envar>MACHTYPE</envar></entry>
	    <entry>The CPU architecture that the system is running
	      on.</entry>
	  </row>

	  <row>
	    <entry><envar>EDITOR</envar></entry>
	    <entry>The user's preferred text editor.</entry>
	  </row>

	  <row>
	    <entry><envar>PAGER</envar></entry>
	    <entry>The user's preferred text pager.</entry>
	  </row>

	  <row>
	    <entry><envar>MANPATH</envar></entry>
	    <entry>Colon-separated list of directories to search for
	      manual pages.</entry>
	  </row>
	</tbody>
      </tgroup>
    </informaltable>

    <indexterm><primary>Bourne shells</primary></indexterm>
    <para>Setting an environment variable differs somewhat from
      shell to shell.  For example, in the C-Style shells such as
      <command>tcsh</command> and <command>csh</command>, you would use
      <command>setenv</command> to set environment variables.
      Under Bourne shells such as <command>sh</command> and
      <command>bash</command>, you would use
      <command>export</command> to set your current environment
      variables.  For example, to set or modify the
      <envar>EDITOR</envar> environment variable, under <command>csh</command> or
      <command>tcsh</command> a
      command like this would set <envar>EDITOR</envar> to
      <filename>/usr/local/bin/emacs</filename>:</para>

    <screen>&prompt.user; <userinput>setenv EDITOR /usr/local/bin/emacs</userinput></screen>

    <para>Under Bourne shells:</para>

    <screen>&prompt.user; <userinput>export EDITOR="/usr/local/bin/emacs"</userinput></screen>

    <para>You can also make most shells expand the environment variable by
      placing a <literal>$</literal> character in front of it on the
      command line.  For example, <command>echo $TERM</command> would
      print out whatever <envar>$TERM</envar> is set to, because the shell
      expands <envar>$TERM</envar> and passes it on to <command>echo</command>.</para>

    <para>Shells treat a lot of special characters, called meta-characters
      as special representations of data.  The most common one is the
      <literal>*</literal> character, which represents any number of
      characters in a filename.  These special meta-characters can be used
      to do filename globbing.  For example, typing in
      <command>echo *</command> is almost the same as typing in
      <command>ls</command> because the shell takes all the files that
      match <literal>*</literal> and puts them on the command line for
      <command>echo</command> to see.</para>

    <para>To prevent the shell from interpreting these special characters,
      they can be escaped from the shell by putting a backslash
      (<literal>\</literal>) character in front of them.  <command>echo
      $TERM</command> prints whatever your terminal is set to.
      <command>echo \$TERM</command> prints <envar>$TERM</envar> as
      is.</para>

    <sect2 id="changing-shells">
      <title>Changing Your Shell</title>

      <para>The easiest way to change your shell is to use the
	<command>chsh</command> command.  Running <command>chsh</command> will
	place you into the editor that is in your <envar>EDITOR</envar>
	environment variable; if it is not set, you will be placed in
	<command>vi</command>.  Change the <quote>Shell:</quote> line
	accordingly.</para>

      <para>You can also give <command>chsh</command> the
	<option>-s</option> option; this will set your shell for you,
	without requiring you to enter an editor.
	For example, if you wanted to
	change your shell to <command>bash</command>, the following should do the
	trick:</para>

      <screen>&prompt.user; <userinput>chsh -s /usr/local/bin/bash</userinput></screen>

      <note>
	<para>The shell that you wish to use <emphasis>must</emphasis> be
	  present in the <filename>/etc/shells</filename> file.  If you
	  have installed a shell from the <link linkend="ports">ports
	  collection</link>, then this should have been done for you
	  already.  If you installed the shell by hand, you must do
	  this.</para>

      <para>For example, if you installed <command>bash</command> by hand
	and placed it into <filename>/usr/local/bin</filename>, you would
	want to:</para>

      <screen>&prompt.root; <userinput>echo &quot;/usr/local/bin/bash&quot; &gt;&gt; /etc/shells</userinput></screen>

       <para>Then rerun <command>chsh</command>.</para>
     </note>
   </sect2>
  </sect1>

  <sect1 id="editors">
    <title>Text Editors</title>
    <indexterm><primary>text editors</primary></indexterm>
    <indexterm><primary>editors</primary></indexterm>

    <para>A lot of configuration in FreeBSD is done by editing text files.
      Because of this, it would be a good idea to become familiar
      with a text editor.  FreeBSD comes with a few as part of the base
      system, and many more are available in the Ports Collection.</para>

    <indexterm>
      <primary><command>ee</command></primary>
    </indexterm>
    <indexterm>
      <primary>editors</primary>
      <secondary><command>ee</command></secondary>
    </indexterm>
    <para>The easiest and simplest editor to learn is an editor called
      <application>ee</application>, which stands for easy editor.  To
      start <application>ee</application>, one would type at the command
      line <command>ee <replaceable>filename</replaceable></command> where
      <replaceable>filename</replaceable> is the name of the file to be edited.
      For example, to edit <filename>/etc/rc.conf</filename>, type in
      <command>ee /etc/rc.conf</command>.  Once inside of
      <command>ee</command>, all of the
      commands for manipulating the editor's functions are listed at the
      top of the display. The caret <literal>^</literal> character represents
      the <keycap>Ctrl</keycap> key on the keyboard, so <literal>^e</literal> expands to the key combination
      <keycombo action="simul"><keycap>Ctrl</keycap><keycap>e</keycap></keycombo>.  To leave
      <application>ee</application>, hit the <keycap>Esc</keycap> key, then choose leave
      editor.  The editor will prompt you to save any changes if the file
      has been modified.</para>

    <indexterm>
      <primary><command>vi</command></primary>
    </indexterm>
    <indexterm>
      <primary>editors</primary>
      <secondary><command>vi</command></secondary>
    </indexterm>
    <indexterm>
      <primary><command>emacs</command></primary>
    </indexterm>
    <indexterm>
      <primary>editors</primary>
      <secondary><command>emacs</command></secondary>
    </indexterm>
    <para>FreeBSD also comes with more powerful text editors such as
      <application>vi</application> as part of the base system, while other editors, like
      <application>Emacs</application> and <application>vim</application>,
      are part of the FreeBSD Ports Collection (<filename role="package">editors/emacs</filename> and <filename role="package">editors/vim</filename>).  These editors offer much
      more functionality and power at the expense of being a little more
      complicated to learn.  However if you plan on doing a lot of text
      editing, learning a more powerful editor such as
      <application>vim</application> or <application>Emacs</application>
      will save you much more time in the long run.</para>

    <para>Many applications which modify files or require typed input
      will automatically open a text editor.  To alter the default
      editor used, set the <envar>EDITOR</envar> environment
      variable.  See <link linkend="shells">shells</link>
      section for more details.</para>
  </sect1>

  <sect1 id="basics-devices">
    <title>Devices and Device Nodes</title>

    <para>A device is a term used mostly for hardware-related
      activities in a system, including disks, printers, graphics
      cards, and keyboards.  When FreeBSD boots, the majority
      of what FreeBSD displays are devices being detected.
      You can look through the boot messages again by viewing
      <filename>/var/run/dmesg.boot</filename>.</para>

    <para>For example, <devicename>acd0</devicename> is the
      first IDE CDROM drive, while <devicename>kbd0</devicename>
      represents the keyboard.</para>

    <para>Most of these devices in a &unix; operating system must be
      accessed through special files called device nodes, which are
      located in the <filename>/dev</filename> directory.</para>

    <sect2>
      <title>Creating Device Nodes</title>
      <para>When adding a new device to your system, or compiling
	in support for additional devices, new device nodes must
	be created.</para>

      <sect3>
	<title><literal>DEVFS</literal> (DEVice File System)</title>

	<para> The device file system, or <literal>DEVFS</literal>, provides access to
	  kernel's device namespace in the global file system namespace.
	  Instead of having to create and modify device nodes,
	  <literal>DEVFS</literal> maintains this particular file system for you.</para>

	<para>See the &man.devfs.5; manual page for more
	  information.</para>
      </sect3>
    </sect2>
  </sect1>

  <sect1 id="binary-formats">
    <title>Binary Formats</title>

    <para>To understand why &os; uses the &man.elf.5;
      format, you must first know a little about the three currently
      <quote>dominant</quote> executable formats for &unix;:</para>

    <itemizedlist>
      <listitem>
        <para>&man.a.out.5;</para>

        <para>The oldest and <quote>classic</quote> &unix; object
          format.  It uses a short and compact header with a magic
          number at the beginning that is often used to characterize
          the format (see &man.a.out.5; for more details).  It
          contains three loaded segments: .text, .data, and .bss plus
          a symbol table and a string table.</para>
      </listitem>

      <listitem>
        <para><acronym>COFF</acronym></para>

        <para>The SVR3 object format.  The header now comprises a
          section table, so you can have more than just .text, .data,
          and .bss sections.</para>
      </listitem>

      <listitem>
        <para>&man.elf.5;</para>

        <para>The successor to <acronym>COFF</acronym>, featuring
          multiple sections and 32-bit or 64-bit possible values.  One
          major drawback: <acronym>ELF</acronym> was also designed
          with the assumption that there would be only one ABI per
          system architecture.  That assumption is actually quite
          incorrect, and not even in the commercial SYSV world (which
          has at least three ABIs: SVR4, Solaris, SCO) does it hold
          true.</para>

        <para>FreeBSD tries to work around this problem somewhat by
          providing a utility for <emphasis>branding</emphasis> a
          known <acronym>ELF</acronym> executable with information
          about the ABI it is compliant with.  See the manual page for
          &man.brandelf.1; for more information.</para>
      </listitem>
    </itemizedlist>

    <para>FreeBSD comes from the <quote>classic</quote> camp and used
      the &man.a.out.5; format, a technology tried and proven through
      many generations of BSD releases, until the beginning of the 3.X
      branch. Though it was possible to build and run native
      <acronym>ELF</acronym> binaries (and kernels) on a FreeBSD
      system for some time before that, FreeBSD initially resisted the
      <quote>push</quote> to switch to <acronym>ELF</acronym> as the
      default format. Why?  Well, when the Linux camp made their
      painful transition to <acronym>ELF</acronym>, it was not so much
      to flee the <filename>a.out</filename> executable format as it
      was their inflexible jump-table based shared library mechanism,
      which made the construction of shared libraries very difficult
      for vendors and developers alike. Since the
      <acronym>ELF</acronym> tools available offered a solution to the
      shared library problem and were generally seen as <quote>the way
      forward</quote> anyway, the migration cost was accepted as
      necessary and the transition made.  FreeBSD's shared library
      mechanism is based more closely on Sun's
      &sunos; style shared library mechanism
      and, as such, is very easy to use.</para>

    <para>So, why are there so many different formats?</para>

    <para>Back in the dim, dark past, there was simple hardware.  This
      simple hardware supported a simple, small system. <filename>a.out</filename> was
      completely adequate for the job of representing binaries on this
      simple system (a PDP-11). As people ported &unix; from this simple
      system, they retained the <filename>a.out</filename> format because it was sufficient
      for the early ports of &unix; to architectures like the Motorola
      68k, VAXen, etc.</para>

    <para>Then some bright hardware engineer decided that if he could
      force software to do some sleazy tricks, then he would be able
      to shave a few gates off the design and allow his CPU core to
      run faster. While it was made to work with this new kind of
      hardware (known these days as <acronym>RISC</acronym>), <filename>a.out</filename>
      was ill-suited for this hardware, so many formats were developed
      to get to a better performance from this hardware than the
      limited, simple <filename>a.out</filename> format could
      offer. Things like <acronym>COFF</acronym>,
      <acronym>ECOFF</acronym>, and a few obscure others were invented
      and their limitations explored before things seemed to settle on
      <acronym>ELF</acronym>.</para>

    <para>In addition, program sizes were getting huge and disks (and
      physical memory) were still relatively small so the concept of a
      shared library was born. The VM system also became more
      sophisticated. While each one of these advancements was done
      using the <filename>a.out</filename> format, its usefulness was
      stretched more and more with each new feature.  In addition,
      people wanted to dynamically load things at run time, or to junk
      parts of their program after the init code had run to save in
      core memory and swap space. Languages became more sophisticated
      and people wanted code called before main automatically. Lots of
      hacks were done to the <filename>a.out</filename> format to
      allow all of these things to happen, and they basically worked
      for a time. In time, <filename>a.out</filename> was not up to
      handling all these problems without an ever increasing overhead
      in code and complexity. While <acronym>ELF</acronym> solved many
      of these problems, it would be painful to switch from the system
      that basically worked. So <acronym>ELF</acronym> had to wait
      until it was more painful to remain with
      <filename>a.out</filename> than it was to migrate to
      <acronym>ELF</acronym>.</para>

    <para>However, as time passed, the build tools that FreeBSD
      derived their build tools from (the assembler and loader
      especially) evolved in two parallel trees. The FreeBSD tree
      added shared libraries and fixed some bugs. The GNU folks that
      originally wrote these programs rewrote them and added simpler
      support for building cross compilers, plugging in different
      formats at will, and so on. Since many people wanted to build cross
      compilers targeting FreeBSD, they were out of luck since the
      older sources that FreeBSD had for <application>as</application> and <application>ld</application> were not up to the
      task. The new GNU tools chain (<application>binutils</application>) does support cross
      compiling, <acronym>ELF</acronym>, shared libraries, C++
      extensions, etc. In addition, many vendors are releasing
      <acronym>ELF</acronym> binaries, and it is a good thing for
      FreeBSD to run them.</para>

    <para><acronym>ELF</acronym> is more expressive than <filename>a.out</filename> and
      allows more extensibility in the base system. The
      <acronym>ELF</acronym> tools are better maintained, and offer
      cross compilation support, which is important to many people.
      <acronym>ELF</acronym> may be a little slower than <filename>a.out</filename>, but
      trying to measure it can be difficult. There are also numerous
      details that are different between the two in how they map
      pages, handle init code, etc. None of these are very important,
      but they are differences. In time support for
      <filename>a.out</filename> will be moved out of the <filename>GENERIC</filename>
      kernel, and eventually removed from the kernel once the need to
      run legacy <filename>a.out</filename> programs is past.</para>
  </sect1>

  <sect1 id="basics-more-information">
    <title>For More Information</title>

    <sect2 id="basics-man">
      <title>Manual Pages</title>
      <indexterm><primary>manual pages</primary></indexterm>

      <para>The most comprehensive documentation on FreeBSD is in the form
	of manual pages. Nearly every program on the system comes with a
	short reference manual explaining the basic operation and various
	arguments. These manuals can be viewed with the <command>man</command> command.  Use
	of the <command>man</command> command is simple:</para>

      <screen>&prompt.user; <userinput>man <replaceable>command</replaceable></userinput></screen>

      <para><literal>command</literal> is the name of the command you
        wish to learn about.  For example, to learn more about
	<command>ls</command> command type:</para>

      <screen>&prompt.user; <userinput>man ls</userinput></screen>

      <para>The online manual is divided up into numbered sections:</para>

      <orderedlist>
	<listitem>
	  <para>User commands.</para>
	</listitem>

	<listitem>
	  <para>System calls and error numbers.</para>
	</listitem>

	<listitem>
	  <para>Functions in the C libraries.</para>
	</listitem>

	<listitem>
	  <para>Device drivers.</para>
	</listitem>

	<listitem>
	  <para>File formats.</para>
	</listitem>

	<listitem>
	  <para>Games and other diversions.</para>
	</listitem>

	<listitem>
	  <para>Miscellaneous information.</para>
	</listitem>

	<listitem>
	  <para>System maintenance and operation commands.</para>
	</listitem>

	<listitem>
	  <para>Kernel developers.</para>
	</listitem>
      </orderedlist>

      <para>In some cases, the same topic may appear in more than one
	section of the online manual.  For example, there is a
	<command>chmod</command> user command and a
	<function>chmod()</function> system call.  In this case, you can
	tell the <command>man</command> command which one you want by specifying the
	section:</para>

      <screen>&prompt.user; <userinput>man 1 chmod</userinput></screen>

      <para>This will display the manual page for the user command
        <command>chmod</command>. References to a particular section of
	the online manual are traditionally placed in parenthesis in
	written documentation, so &man.chmod.1; refers to the
	<command>chmod</command> user command and &man.chmod.2; refers to
	the system call.</para>

      <para>This is fine if you know the name of the command and just
	wish to know how to use it, but what if you cannot recall the
	command name?  You can use <command>man</command> to search for keywords in the
	command descriptions by using the <option>-k</option>
	switch:</para>

      <screen>&prompt.user; <userinput>man -k mail</userinput></screen>

      <para>With this command you will be presented with a list of
        commands that have the keyword <quote>mail</quote> in their
	descriptions.  This is actually functionally equivalent to using
	the <command>apropos</command> command.</para>

      <para>So, you are looking at all those fancy commands in
	<filename>/usr/bin</filename> but do not have the faintest idea
	what most of them actually do?  Type:</para>

	<screen>&prompt.user; <userinput>cd /usr/bin</userinput>
&prompt.user; <userinput>man -f *</userinput></screen>

	<para>or</para>

	<screen>&prompt.user; <userinput>cd /usr/bin</userinput>
&prompt.user; <userinput>whatis *</userinput></screen>

	<para>which does the same thing.</para>
    </sect2>

    <sect2 id="basics-info">
      <title>GNU Info Files</title>
      <indexterm><primary>Free Software Foundation</primary></indexterm>

      <para>FreeBSD includes many applications and utilities produced by
	the Free Software Foundation (FSF).  In addition to manual pages,
	these programs come with more extensive hypertext documents called
	<literal>info</literal> files which can be viewed with the
	<command>info</command> command or, if you installed
	<application>emacs</application>, the info mode of
	<application>emacs</application>.</para>

      <para>To use the &man.info.1; command, type:</para>

      <screen>&prompt.user; <userinput>info</userinput></screen>

      <para>For a brief introduction, type <literal>h</literal>.  For a
	quick command reference, type <literal>?</literal>.</para>
    </sect2>
  </sect1>
</chapter>