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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. |