man.bsd.lv manual page server

Manual Page Search Parameters
KENV(1) General Commands Manual KENV(1)

kenv — dump or modify the kernel environment

kenv [-hNq]

kenv [-qv] variable[=value]

kenv [-q] -u variable

The kenv utility will dump the kernel environment if invoked without arguments. If the -h option is specified, it will limit the report to kernel probe hints. If an optional variable name is specified, kenv will only report that value. If the -N option is specified, kenv will only display variable names and not their values. If the -u option is specified, kenv will delete the given environment variable. If the environment variable is followed by an optional value, kenv will set the environment variable to this value.

If the -q option is set, warnings normally printed as a result of being unable to perform the requested operation will be suppressed.

If the -v option is set, the variable name will be printed out for the environment variable in addition to the value when kenv is executed with a variable name.

Variables can be added to the kernel environment using the /boot/loader.conf file, or also statically compiled into the kernel using the statement

env filename

in the kernel config file. The file can contain lines of the form

name = value # this is a comment

where whitespace around ‘name’ and ‘=’, and everything after a ‘#’ character, are ignored. Almost any printable character except ‘=’ is acceptable as part of a name. Quotes are optional and necessary only if the value contains whitespace.

Show kernel probe hints variable names and filter for the uart device

$ 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

Show the value of a specific variable:

$ kenv hint.uart.1.at
isa

Same as above but adding the name of the variable in the report:

$ kenv -v hint.uart.1.at
hint.uart.1.at="isa"

Try to delete a variable and suppress warnings if any:

$ kenv -q -u hint.uart.1.at

Set the value of the verbose_loading variable

$ kenv verbose_loading="YES"
verbose_loading="YES"

kenv(2), config(5), loader.conf(5), loader(8)

The kenv utility appeared in FreeBSD 4.1.1.

October 5, 2020 FreeBSD-13.0