.\"-
.\" Copyright (c) 2000 Peter Wemm <peter@FreeBSD.org>
.\"
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.\" modification, are permitted provided that the following conditions
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.\" $FreeBSD$
.\"
.Dd June 20, 2021
.Dt KENV 1
.Os
.Sh NAME
.Nm kenv
.Nd list or modify the kernel environment
.Sh SYNOPSIS
.Nm
.Op Fl l | s
.Op Fl hNq
.Nm
.Op Fl qv
.Ar variable Ns Op = Ns Ar value
.Nm
.Op Fl q
.Fl u
.Ar variable
.Sh DESCRIPTION
The
.Nm
utility will list all variables in the kernel environment if
invoked without arguments.
.Pp
If the
.Fl l
option is specified, then the static environment provided by
.Xr loader 8
will be listed instead.
Similarly, the
.Fl s
option will list the static environment defined by the kernel config.
Both of the
.Fl l
and
.Fl s
options are dependent on the kernel being configured to preserve early kernel
environments.
The default kernel configuration does not preserve these environments.
.Pp
If the
.Fl h
option is specified, it will limit the report to kernel probe hints.
If an optional
.Ar variable
name is specified,
.Nm
will only report that value.
If the
.Fl N
option is specified,
.Nm
will only display variable names and not their values.
If the
.Fl u
option is specified,
.Nm
will delete the given environment variable.
If the environment variable is followed by an optional
.Ar value ,
.Nm
will set the environment variable to this value.
.Pp
If the
.Fl q
option is set, warnings normally printed as a result of being unable to
perform the requested operation will be suppressed.
.Pp
If the
.Fl v
option is set, the variable name will be printed out for the
environment variable in addition to the value when
.Nm
is executed with a variable name.
.Pp
Variables can be added to the kernel environment using the
.Pa /boot/loader.conf
file, or also statically compiled into the kernel using the statement
.Pp
.Dl Ic env Ar filename
.Pp
in the kernel config file.
The file can contain lines of the form
.Pp
.Dl name = "value" # this is a comment
.Pp
where whitespace around
.Sq name
and
.Sq = ,
and everything after a
.Sq #
character, are ignored.
Almost any printable character except
.Sq =
is acceptable as part of a name.
Quotes are optional and necessary only if the value contains whitespace.
.Sh EXAMPLES
Show kernel probe hints variable names and filter for the uart
device
.Bd -literal -offset indent
$ kenv -h -N | grep uart
hint.uart.0.at
hint.uart.0.flags
hint.uart.0.irq
hint.uart.0.port
hint.uart.1.at
hint.uart.1.irq
hint.uart.1.port
.Ed
.Pp
Show the value of a specific variable:
.Bd -literal -offset indent
$ kenv hint.uart.1.at
isa
.Ed
.Pp
Same as above but adding the name of the variable in the report:
.Bd -literal -offset indent
$ kenv -v hint.uart.1.at
hint.uart.1.at="isa"
.Ed
.Pp
Try to delete a variable and suppress warnings if any:
.Bd -literal -offset indent
$ kenv -q -u hint.uart.1.at
.Ed
.Pp
Set the value of the
.Ev verbose_loading
variable
.Bd -literal -offset indent
$ kenv verbose_loading="YES"
verbose_loading="YES"
.Ed
.Sh SEE ALSO
.Xr kenv 2 ,
.Xr config 5 ,
.Xr loader.conf 5 ,
.Xr loader 8
.Sh HISTORY
The
.Nm
utility appeared in
.Fx 4.1.1 .
