[thirdparty/systemd.git] / ENVIRONMENT.md

# Known Environment Variables

A number of systemd components take additional runtime parameters via
environment variables. Many of these environment variables are not supported at
the same level as command line switches and other interfaces are: we don't
document them in the man pages and we make no stability guarantees for
them. While they generally are unlikely to be dropped any time soon again, we
do not want to guarantee that they stay around for good either.

Below is an (incomprehensive) list of the environment variables understood by
the various tools. Note that this list only covers environment variables not
documented in the proper man pages.

All tools:

* `$SYSTEMD_IGNORE_CHROOT=1` — if set, don't check whether being invoked in a
  chroot() environment. This is particularly relevant for systemctl, as it will
  not alter its behaviour for chroot() environments if set. (Normally it
  refrains from talking to PID 1 in such a case.)

* `$SD_EVENT_PROFILE_DELAYS=1` — if set, the sd-event event loop implementation
  will print latency information at runtime.

* `$SYSTEMD_PROC_CMDLINE` — if set, may contain a string that is used as kernel
  command line instead of the actual one readable from /proc/cmdline. This is
  useful for debugging, in order to test generators and other code against
  specific kernel command lines.

systemctl:

* `$SYSTEMCTL_FORCE_BUS=1` — if set, do not connect to PID1's private D-Bus
  listener, and instead always connect through the dbus-daemon D-bus broker.

* `$SYSTEMCTL_INSTALL_CLIENT_SIDE=1` — if set, enable or disable unit files on
  the client side, instead of asking PID 1 to do this.

* `$SYSTEMCTL_SKIP_SYSV=1` — if set, do not call out to SysV compatibility hooks.

systemd-nspawn:

* `$UNIFIED_CGROUP_HIERARCHY=1` — if set, force nspawn into unified cgroup
  hierarchy mode.

* `$SYSTEMD_NSPAWN_API_VFS_WRITABLE=1` — if set, make /sys and /proc/sys and
  friends writable in the container. If set to "network", leave only
  /proc/sys/net writable.

* `$SYSTEMD_NSPAWN_CONTAINER_SERVICE=…` — override the "service" name nspawn
  uses to register with machined. If unset defaults to "nspawn", but with this
  variable may be set to any other value.

* `$SYSTEMD_NSPAWN_USE_CGNS=0` — if set, do not use cgroup namespacing, even if
  it is available.

* `$SYSTEMD_NSPAWN_LOCK=0` — if set, do not lock container images when running.

systemd-logind:

* `$SYSTEMD_BYPASS_HIBERNATION_MEMORY_CHECK=1` — if set, report that
  hibernation is available even if the swap devices do not provide enough room
  for it.

installed systemd tests:

* `$SYSTEMD_TEST_DATA` — override the location of test data. This is useful if
  a test executable is moved to an arbitrary location.

nss-systemd:

* `$SYSTEMD_NSS_BYPASS_SYNTHETIC=1` — if set, `nss-systemd` won't synthesize
  user/group records for the `root` and `nobody` users if they are missing from
  `/etc/passwd`.

* `$SYSTEMD_NSS_DYNAMIC_BYPASS=1` — if set, `nss-systemd` won't return
  user/group records for dynamically registered service users (i.e. users
  registered through `DynamicUser=1`).

* `$SYSTEMD_NSS_BYPASS_BUS=1` — if set, `nss-systemd` won't use D-Bus to do
  dynamic user lookups. This is primarily useful to make `nss-systemd` work
  safely from within `dbus-daemon`.
Commit	Line	Data
4549fcdb LP	1	# Known Environment Variables
	2
	3	A number of systemd components take additional runtime parameters via
	4	environment variables. Many of these environment variables are not supported at
	5	the same level as command line switches and other interfaces are: we don't
	6	document them in the man pages and we make no stability guarantees for
	7	them. While they generally are unlikely to be dropped any time soon again, we
	8	do not want to guarantee that they stay around for good either.
	9
	10	Below is an (incomprehensive) list of the environment variables understood by
	11	the various tools. Note that this list only covers environment variables not
	12	documented in the proper man pages.
	13
	14	All tools:
	15
	16	* `$SYSTEMD_IGNORE_CHROOT=1` — if set, don't check whether being invoked in a
	17	chroot() environment. This is particularly relevant for systemctl, as it will
	18	not alter its behaviour for chroot() environments if set. (Normally it
	19	refrains from talking to PID 1 in such a case.)
	20
	21	* `$SD_EVENT_PROFILE_DELAYS=1` — if set, the sd-event event loop implementation
	22	will print latency information at runtime.
	23
2467cc55 LP	24	* `$SYSTEMD_PROC_CMDLINE` — if set, may contain a string that is used as kernel
	25	command line instead of the actual one readable from /proc/cmdline. This is
	26	useful for debugging, in order to test generators and other code against
	27	specific kernel command lines.
	28
4549fcdb LP	29	systemctl:
	30
	31	* `$SYSTEMCTL_FORCE_BUS=1` — if set, do not connect to PID1's private D-Bus
	32	listener, and instead always connect through the dbus-daemon D-bus broker.
	33
	34	* `$SYSTEMCTL_INSTALL_CLIENT_SIDE=1` — if set, enable or disable unit files on
	35	the client side, instead of asking PID 1 to do this.
	36
	37	* `$SYSTEMCTL_SKIP_SYSV=1` — if set, do not call out to SysV compatibility hooks.
	38
	39	systemd-nspawn:
	40
	41	* `$UNIFIED_CGROUP_HIERARCHY=1` — if set, force nspawn into unified cgroup
	42	hierarchy mode.
	43
	44	* `$SYSTEMD_NSPAWN_API_VFS_WRITABLE=1` — if set, make /sys and /proc/sys and
	45	friends writable in the container. If set to "network", leave only
	46	/proc/sys/net writable.
	47
	48	* `$SYSTEMD_NSPAWN_CONTAINER_SERVICE=…` — override the "service" name nspawn
	49	uses to register with machined. If unset defaults to "nspawn", but with this
	50	variable may be set to any other value.
	51
	52	* `$SYSTEMD_NSPAWN_USE_CGNS=0` — if set, do not use cgroup namespacing, even if
	53	it is available.
	54
	55	* `$SYSTEMD_NSPAWN_LOCK=0` — if set, do not lock container images when running.
	56
	57	systemd-logind:
	58
	59	* `$SYSTEMD_BYPASS_HIBERNATION_MEMORY_CHECK=1` — if set, report that
	60	hibernation is available even if the swap devices do not provide enough room
	61	for it.
94fa1497 ZJS	62
	63	installed systemd tests:
	64
	65	* `$SYSTEMD_TEST_DATA` — override the location of test data. This is useful if
	66	a test executable is moved to an arbitrary location.
dba1bd43 LP	67
	68	nss-systemd:
	69
	70	* `$SYSTEMD_NSS_BYPASS_SYNTHETIC=1` — if set, `nss-systemd` won't synthesize
	71	user/group records for the `root` and `nobody` users if they are missing from
	72	`/etc/passwd`.
	73
	74	* `$SYSTEMD_NSS_DYNAMIC_BYPASS=1` — if set, `nss-systemd` won't return
	75	user/group records for dynamically registered service users (i.e. users
	76	registered through `DynamicUser=1`).
	77
	78	* `$SYSTEMD_NSS_BYPASS_BUS=1` — if set, `nss-systemd` won't use D-Bus to do
	79	dynamic user lookups. This is primarily useful to make `nss-systemd` work
	80	safely from within `dbus-daemon`.