Editing Kenv

{{welcome}}
{{Navbar Kernel Competence}}

==Introduction==

With [https://www.freebsd.org/cgi/man.cgi?kenv(1) kenv(1)] you can dump or modify the kernel environment.
The [https://www.freebsd.org/cgi/man.cgi?query=kenv&sektion=2&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports kenv(2)] system call manipulates	kernel environment variables.  It supports the well known userland actions of getting, setting and unsetting   environment variables, as well as the ability to dump all of the entries   in	the kernel environment.

==Usage==



===Kenv without options===
If you you write:  <code>kenv</code>
in your terminal, you will get the complete ''kernel environment'' tree.
These variables are the loader variables and relate to initial hardware probes. The right decision has to be made before anything in the kernel accesses the specific hardware.

'''Example'''<br/>
/u/h/yourusername> '''kenv<br/>
{|class="wikitable" style="width:75.5%;background:#FFFFFF; border:2px solid #008000;text-align:left;padding: 10px" 
|-
|LINES="24"
|-
|acpi.oem="ACPIAM"
|-
|acpi.revision="1"
|-
|acpi.rsdp="0x000facd0"
|-
|acpi.rsdt="0xcffa0000"
|-
|acpi_load="YES"
|-
|autoboot_delay="02"
|-
|boot_mute="YES"
|-
|bootenv_autolist="YES"
|-
|bootenvs[0]="zfs:tank/ROOT/initial"
|-
|bootenvs_count="1"
|-
|bootfile="kernel"
|-
|comconsole_pcidev=""
|-
|comconsole_port="1016"
|-
|comconsole_speed="9600"
|-
|console="vidconsole"
|-
|currdev="zfs:tank/ROOT/initial:"
|-
|efi_max_resolution="1x1"
|-
|hint.acpi.0.disabled="0"
|-
|hint.acpi.0.oem="ACPIAM"
|-
|hint.acpi.0.revision="1"
|-
|hint.acpi.0.rsdp="0x000facd0"
|-
|hint.acpi.0.rsdt="0xcffa0000"
|-
|hint.acpi_throttle.0.disabled="1"
|-
|hint.atkbd.0.at="atkbdc"
|-
|hint.atkbd.0.irq="1"
|-
|hint.atkbdc.0.at="isa"
|-
|hint.atkbdc.0.port="0x060"
|-
|hint.atrtc.0.at="isa"
|-
|hint.atrtc.0.irq="8"
|-
|hint.atrtc.0.port="0x70"
|-
|hint.attimer.0.at="isa"
|-
|hint.attimer.0.irq="0"
|-
|hint.attimer.0.port="0x40"
|-
|hint.fd.0.at="fdc0"
|-
|hint.fd.0.drive="0"
|-
|hint.fd.1.at="fdc0"
|-
|hint.fd.1.drive="1"
|-
|hint.fdc.0.at="isa"
|-
|hint.fdc.0.drq="2"
|-
|hint.fdc.0.irq="6"
|-
|hint.fdc.0.port="0x3F0"
|-
|hint.p4tcc.0.disabled="1"
|-
|hint.ppc.0.at="isa"
|-
|hint.ppc.0.irq="7"
|-
|hint.psm.0.at="atkbdc"
|-
|hint.psm.0.irq="12"
|-
|hint.sc.0.at="isa"
|-
|hint.sc.0.flags="0x100"
|-
|hint.uart.0.at="isa"
|-
|hint.uart.0.flags="0x10"
|-
|hint.uart.0.irq="4"
|-
|hint.uart.0.port="0x3F8"
|-
|hint.uart.1.at="isa"
|-
|hint.uart.1.irq="3"
|-
|hint.uart.1.port="0x2F8"
|-
|hw.memtest.tests="0"
|-
|hw.psm.synaptics_support="1"
|-
|hw.usb.no_boot_wait="1"
|-
|kern.geom.eli.visible_passphrase="2"
|-
|kernel="kernel"
|-
|kernel_options=""
|-
|kernel_path="/boot/kernel"
|-
|kernelname="/boot/kernel/kernel"
|-
|kernels_autodetect="YES"
|-
|legal.intel_ipw.license_ack="1"
|-
|legal.intel_iwi.license_ack="1"
|-
|legal.realtek.license_ack="1"
|-
|loaddev="zfs:tank/ROOT/initial:"
|-
|loader_brand="ghostbsd"
|-
|loader_conf_files="/boot/device.hints /boot/loader.conf /boot/loader.conf.local"
|-
|loader_logo="ghostbsd"
|-
|loader_menu_title="Welcome to GhostBSD"
|-
|module_blacklist="drm drm2 radeonkms i915kms amdgpu"
|-
|module_path="/boot/kernel;/boot/modules;/boot/dtb;/boot/dtb/overlays"
|-
|net.inet.ip.fw.default_to_accept="1"
|-
|nextboot_conf="/boot/nextboot.conf"
|-
|nextboot_enable="NO"
|-
|pcibios.config1="1"
|-
|pcibios.config2="0"
|-
|pcibios.major="3"
|-
|pcibios.maxbus="5"
|-
|pcibios.minor="0"
|-
|rc_system="openrc"
|-
|script.lang="lua"
|-
|smbios.bios.reldate="07/07/2009"
|-
|smbios.bios.vendor="American Megatrends Inc."
|-
|smbios.bios.version="080015 "
|-
|smbios.chassis.maker="ECS"
|-
|smbios.chassis.serial="                      "
|-
|smbios.chassis.tag="                      "
|-
|smbios.chassis.version="                      "
|-
|smbios.memory.enabled="4194304"
|-
|smbios.planar.location="                      "
|-
|smbios.planar.maker="ECS"
|-
|smbios.planar.product="GF8100VM-M5"
|-
|smbios.planar.serial="                      "
|-
|smbios.planar.tag="                      "
|-
|smbios.planar.version="1.0                   "
|-
|smbios.socket.enabled="1"
|-
|smbios.socket.populated="1"
|-
|smbios.system.family="                      "
|-
|smbios.system.maker="ECS"
|-
|smbios.system.product="GF8100VM-M5"
|-
|smbios.system.serial="                      "
|-
|smbios.system.sku="                      "
|-
|smbios.system.uuid="03000200-0400-0500-0006-000700080009"
|-
|smbios.system.version="1.0"
|-
|smbios.version="2.6"
|-
|twiddle_divisor="1"
|-
|verbose_loading="NO"
|-
|vfs.root.mountfrom="zfs:tank/ROOT/initial"
|-
|vfs.zfs.arc_max="512M"
|-
|vfs.zfs.boot.primary_pool="2274887038975416023"
|-
|vfs.zfs.boot.primary_vdev="13128611794753525809"
|-
|zfs_be_active="zfs:tank/ROOT/initial"
|-
|zfs_be_currpage="1"
|-
|zfs_be_root="tank/ROOT"
|}

Kernel environment variables can be set in the ''/boot/loader.conf''  

===Options===

'''There are following options:'''
* <code>>kenv -h</code> ''-h'' 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

<code>env ''filename''</code>

in	the kernel config file.	 The file can contain lines of the form
<code>   name	= value	</code> <nowiki># </nowiki>this is a comment

where whitespace around `name' and	`=', and everything after a `<nowiki># </nowiki>'	character, are	ignored.  Almost any printable character except	`=' is accept able as part of a name.  Quotes are optional and necessary only if	the  value contains whitespace.

'''Attention''': The kernel environment variables are also tunable. Before you play with them, reed the man pages. It is possible to crash your system with a false value. 














[[Category:Kernel]]
@@ Line 280: / Line 280: @@
 '''Attention''': The kernel environment variables are also tunable. Before you play with them, reed the man pages. It is possible to crash your system with a false value.
-===The Action	Argument===
-The action	argument can be	one of the following:
-{|class="wikitable" style="width:96.5%;background:#FFFFFF; border:2px solid #008000;text-align:left;padding: 10px"
-|-
-!scope="col" style="width: 100px;"|'''Action'''
-!scope="col" style="width: 500px;"|'''Desciption'''
-|-
-|KENV_GET	|| Get the value of the variable with the	given name.  The size
-		 of the	value buffer is	given by len, which should be at least
-		 KENV_MVALLEN +	1 bytes	to avoid truncation and	to ensure NUL
-		 termination.
-|-
-|    KENV_SET||	 Set or	add a variable.	 The name and value are	limited	to
-		 KENV_MNAMELEN and KENV_MVALLEN	characters, respectively (not
-		 including the NUL terminator.)	The len	argument indicates the
-		 length	of the value and must include the NUL terminator.
-		 This option is	only available to the superuser.
-|-
-|KENV_UNSET	|| Unset the variable with the given name.  The value and	len
-		 arguments are ignored.	 This option is	only available to the
-		 superuser.
-|-
-|KENV_DUMP	|| Dump as much of the kernel environment	as will	fit in value,
-		 whose size is given in	len.  If value is NULL,	kenv() will
-		 return	the number of bytes required to	copy out the entire
-		 environment.  The name	is ignored.
-|}