]>
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 | ||
f38951a6 CW |
16 | * `$SYSTEMD_OFFLINE=[0|1]` — if set to `1`, then `systemctl` will |
17 | refrain from talking to PID 1; this has the same effect as the historical | |
18 | detection of `chroot()`. Setting this variable to `0` instead has a similar | |
19 | effect as `SYSTEMD_IGNORE_CHROOT=1`; i.e. tools will try to | |
20 | communicate with PID 1 even if a `chroot()` environment is detected. | |
21 | You almost certainly want to set this to `1` if you maintain a package build system | |
22 | or similar and are trying to use a modern container system and not plain | |
23 | `chroot()`. | |
24 | ||
4549fcdb | 25 | * `$SYSTEMD_IGNORE_CHROOT=1` — if set, don't check whether being invoked in a |
f38951a6 CW |
26 | `chroot()` environment. This is particularly relevant for systemctl, as it |
27 | will not alter its behaviour for `chroot()` environments if set. Normally it | |
28 | refrains from talking to PID 1 in such a case; turning most operations such | |
29 | as `start` into no-ops. If that's what's explicitly desired, you might | |
30 | consider setting `SYSTEMD_OFFLINE=1`. | |
4549fcdb LP |
31 | |
32 | * `$SD_EVENT_PROFILE_DELAYS=1` — if set, the sd-event event loop implementation | |
33 | will print latency information at runtime. | |
34 | ||
2467cc55 LP |
35 | * `$SYSTEMD_PROC_CMDLINE` — if set, may contain a string that is used as kernel |
36 | command line instead of the actual one readable from /proc/cmdline. This is | |
37 | useful for debugging, in order to test generators and other code against | |
38 | specific kernel command lines. | |
39 | ||
385b2eb2 YW |
40 | * `$SYSTEMD_BUS_TIMEOUT=SECS` — specifies the maximum time to wait for method call |
41 | completion. If no time unit is specified, assumes seconds. The usual other units | |
42 | are understood, too (us, ms, s, min, h, d, w, month, y). If it is not set or set | |
43 | to 0, then the built-in default is used. | |
44 | ||
b4f60743 LP |
45 | * `$SYSTEMD_MEMPOOL=0` — if set the internal memory caching logic employed by |
46 | hash tables is turned off, and libc malloc() is used for all allocations. | |
47 | ||
4549fcdb LP |
48 | systemctl: |
49 | ||
50 | * `$SYSTEMCTL_FORCE_BUS=1` — if set, do not connect to PID1's private D-Bus | |
51 | listener, and instead always connect through the dbus-daemon D-bus broker. | |
52 | ||
53 | * `$SYSTEMCTL_INSTALL_CLIENT_SIDE=1` — if set, enable or disable unit files on | |
54 | the client side, instead of asking PID 1 to do this. | |
55 | ||
56 | * `$SYSTEMCTL_SKIP_SYSV=1` — if set, do not call out to SysV compatibility hooks. | |
57 | ||
58 | systemd-nspawn: | |
59 | ||
60 | * `$UNIFIED_CGROUP_HIERARCHY=1` — if set, force nspawn into unified cgroup | |
61 | hierarchy mode. | |
62 | ||
63 | * `$SYSTEMD_NSPAWN_API_VFS_WRITABLE=1` — if set, make /sys and /proc/sys and | |
64 | friends writable in the container. If set to "network", leave only | |
65 | /proc/sys/net writable. | |
66 | ||
67 | * `$SYSTEMD_NSPAWN_CONTAINER_SERVICE=…` — override the "service" name nspawn | |
68 | uses to register with machined. If unset defaults to "nspawn", but with this | |
69 | variable may be set to any other value. | |
70 | ||
71 | * `$SYSTEMD_NSPAWN_USE_CGNS=0` — if set, do not use cgroup namespacing, even if | |
72 | it is available. | |
73 | ||
74 | * `$SYSTEMD_NSPAWN_LOCK=0` — if set, do not lock container images when running. | |
75 | ||
1099ceeb LP |
76 | * `$SYSTEMD_NSPAWN_TMPFS_TMP=0` — if set, do not overmount /tmp in the |
77 | container with a tmpfs, but leave the directory from the image in place. | |
78 | ||
4549fcdb LP |
79 | systemd-logind: |
80 | ||
81 | * `$SYSTEMD_BYPASS_HIBERNATION_MEMORY_CHECK=1` — if set, report that | |
82 | hibernation is available even if the swap devices do not provide enough room | |
83 | for it. | |
94fa1497 ZJS |
84 | |
85 | installed systemd tests: | |
86 | ||
87 | * `$SYSTEMD_TEST_DATA` — override the location of test data. This is useful if | |
88 | a test executable is moved to an arbitrary location. | |
dba1bd43 LP |
89 | |
90 | nss-systemd: | |
91 | ||
92 | * `$SYSTEMD_NSS_BYPASS_SYNTHETIC=1` — if set, `nss-systemd` won't synthesize | |
93 | user/group records for the `root` and `nobody` users if they are missing from | |
94 | `/etc/passwd`. | |
95 | ||
96 | * `$SYSTEMD_NSS_DYNAMIC_BYPASS=1` — if set, `nss-systemd` won't return | |
97 | user/group records for dynamically registered service users (i.e. users | |
98 | registered through `DynamicUser=1`). | |
99 | ||
100 | * `$SYSTEMD_NSS_BYPASS_BUS=1` — if set, `nss-systemd` won't use D-Bus to do | |
101 | dynamic user lookups. This is primarily useful to make `nss-systemd` work | |
102 | safely from within `dbus-daemon`. | |
41d0da0f YW |
103 | |
104 | systemd-timedated: | |
105 | ||
106 | * `$SYSTEMD_TIMEDATED_NTP_SERVICES=…` — colon-separated list of unit names of | |
107 | NTP client services. If set, `timedatectl set-ntp on` enables and starts the | |
108 | first existing unit listed in the environment variable, and | |
109 | `timedatectl set-ntp off` disables and stops all listed units. | |
39922217 LP |
110 | |
111 | systemd itself: | |
112 | ||
113 | * `$SYSTEMD_ACTIVATION_UNIT` — set for all NSS and PAM module invocations that | |
114 | are done by the service manager on behalf of a specific unit, in child | |
115 | processes that are later (after execve()) going to become unit | |
116 | processes. Contains the full unit name (e.g. "foobar.service"). NSS and PAM | |
117 | modules can use this information to determine in which context and on whose | |
118 | behalf they are being called, which may be useful to avoid deadlocks, for | |
119 | example to bypass IPC calls to the very service that is about to be | |
120 | started. Note that NSS and PAM modules should be careful to only rely on this | |
121 | data when invoked privileged, or possibly only when getppid() returns 1, as | |
122 | setting environment variables is of course possible in any even unprivileged | |
123 | contexts. | |
124 | ||
125 | * `$SYSTEMD_ACTIVATION_SCOPE` — closely related to `$SYSTEMD_ACTIVATION_UNIT`, | |
126 | it is either set to `system` or `user` depending on whether the NSS/PAM | |
127 | module is called by systemd in `--system` or `--user` mode. |