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c3e270f4 FB |
1 | --- |
2 | title: Known Environment Variables | |
4cdca0af | 3 | category: Interfaces |
b41a3f66 | 4 | layout: default |
0aff7b75 | 5 | SPDX-License-Identifier: LGPL-2.1-or-later |
c3e270f4 FB |
6 | --- |
7 | ||
4549fcdb LP |
8 | # Known Environment Variables |
9 | ||
10 | A number of systemd components take additional runtime parameters via | |
11 | environment variables. Many of these environment variables are not supported at | |
12 | the same level as command line switches and other interfaces are: we don't | |
13 | document them in the man pages and we make no stability guarantees for | |
14 | them. While they generally are unlikely to be dropped any time soon again, we | |
15 | do not want to guarantee that they stay around for good either. | |
16 | ||
17 | Below is an (incomprehensive) list of the environment variables understood by | |
18 | the various tools. Note that this list only covers environment variables not | |
19 | documented in the proper man pages. | |
20 | ||
21 | All tools: | |
22 | ||
e7b86e48 ZJS |
23 | * `$SYSTEMD_OFFLINE=[0|1]` — if set to `1`, then `systemctl` will refrain from |
24 | talking to PID 1; this has the same effect as the historical detection of | |
25 | `chroot()`. Setting this variable to `0` instead has a similar effect as | |
54dcf847 LP |
26 | `$SYSTEMD_IGNORE_CHROOT=1`; i.e. tools will try to communicate with PID 1 |
27 | even if a `chroot()` environment is detected. You almost certainly want to | |
28 | set this to `1` if you maintain a package build system or similar and are | |
29 | trying to use a modern container system and not plain `chroot()`. | |
f38951a6 | 30 | |
4549fcdb | 31 | * `$SYSTEMD_IGNORE_CHROOT=1` — if set, don't check whether being invoked in a |
f38951a6 | 32 | `chroot()` environment. This is particularly relevant for systemctl, as it |
e7b86e48 | 33 | will not alter its behaviour for `chroot()` environments if set. Normally it |
f38951a6 CW |
34 | refrains from talking to PID 1 in such a case; turning most operations such |
35 | as `start` into no-ops. If that's what's explicitly desired, you might | |
54dcf847 | 36 | consider setting `$SYSTEMD_OFFLINE=1`. |
4549fcdb LP |
37 | |
38 | * `$SD_EVENT_PROFILE_DELAYS=1` — if set, the sd-event event loop implementation | |
39 | will print latency information at runtime. | |
40 | ||
53aa0d02 | 41 | * `$SYSTEMD_PROC_CMDLINE` — if set, the contents are used as the kernel command |
e7b86e48 | 42 | line instead of the actual one in `/proc/cmdline`. This is useful for |
53aa0d02 ZJS |
43 | debugging, in order to test generators and other code against specific kernel |
44 | command lines. | |
45 | ||
df78419d ZJS |
46 | * `$SYSTEMD_OS_RELEASE` — if set, use this path instead of `/etc/os-release` or |
47 | `/usr/lib/os-release`. When operating under some root (e.g. `systemctl | |
5cf69e70 | 48 | --root=…`), the path is prefixed with the root. Only useful for debugging. |
df78419d | 49 | |
e7b86e48 | 50 | * `$SYSTEMD_FSTAB` — if set, use this path instead of `/etc/fstab`. Only useful |
ed4ad488 ZJS |
51 | for debugging. |
52 | ||
99e3d476 ZJS |
53 | * `$SYSTEMD_SYSROOT_FSTAB` — if set, use this path instead of |
54 | `/sysroot/etc/fstab`. Only useful for debugging `systemd-fstab-generator`. | |
55 | ||
905dd992 LF |
56 | * `$SYSTEMD_SYSFS_CHECK` — takes a boolean. If set, overrides sysfs container |
57 | detection that ignores `/dev/` entries in fstab. Only useful for debugging | |
58 | `systemd-fstab-generator`. | |
59 | ||
e7b86e48 ZJS |
60 | * `$SYSTEMD_CRYPTTAB` — if set, use this path instead of `/etc/crypttab`. Only |
61 | useful for debugging. Currently only supported by | |
62 | `systemd-cryptsetup-generator`. | |
a6c57e74 | 63 | |
1f1a2243 TA |
64 | * `$SYSTEMD_INTEGRITYTAB` — if set, use this path instead of |
65 | `/etc/integritytab`. Only useful for debugging. Currently only supported by | |
66 | `systemd-integritysetup-generator`. | |
67 | ||
e7b86e48 ZJS |
68 | * `$SYSTEMD_VERITYTAB` — if set, use this path instead of |
69 | `/etc/veritytab`. Only useful for debugging. Currently only supported by | |
70 | `systemd-veritysetup-generator`. | |
08b04ec7 | 71 | |
2536752d | 72 | * `$SYSTEMD_EFI_OPTIONS` — if set, used instead of the string in the |
e7b86e48 | 73 | `SystemdOptions` EFI variable. Analogous to `$SYSTEMD_PROC_CMDLINE`. |
2467cc55 | 74 | |
05c6f341 ZJS |
75 | * `$SYSTEMD_DEFAULT_HOSTNAME` — override the compiled-in fallback hostname |
76 | (relevant in particular for the system manager and `systemd-hostnamed`). | |
77 | Must be a valid hostname (either a single label or a FQDN). | |
78 | ||
b1fd5cd4 ZJS |
79 | * `$SYSTEMD_IN_INITRD` — takes a boolean. If set, overrides initrd detection. |
80 | This is useful for debugging and testing initrd-only programs in the main | |
81 | system. | |
0307ea49 | 82 | |
385b2eb2 YW |
83 | * `$SYSTEMD_BUS_TIMEOUT=SECS` — specifies the maximum time to wait for method call |
84 | completion. If no time unit is specified, assumes seconds. The usual other units | |
85 | are understood, too (us, ms, s, min, h, d, w, month, y). If it is not set or set | |
86 | to 0, then the built-in default is used. | |
87 | ||
5f1b0cc6 | 88 | * `$SYSTEMD_MEMPOOL=0` — if set, the internal memory caching logic employed by |
e7b86e48 | 89 | hash tables is turned off, and libc `malloc()` is used for all allocations. |
b4f60743 | 90 | |
71ea8436 LP |
91 | * `$SYSTEMD_UTF8=` — takes a boolean value, and overrides whether to generate |
92 | non-ASCII special glyphs at various places (i.e. "→" instead of | |
1a127aa0 | 93 | "->"). Usually this is determined automatically, based on `$LC_CTYPE`, but in |
71ea8436 LP |
94 | scenarios where locale definitions are not installed it might make sense to |
95 | override this check explicitly. | |
96 | ||
e7b86e48 | 97 | * `$SYSTEMD_EMOJI=0` — if set, tools such as `systemd-analyze security` will |
5f1b0cc6 LP |
98 | not output graphical smiley emojis, but ASCII alternatives instead. Note that |
99 | this only controls use of Unicode emoji glyphs, and has no effect on other | |
100 | Unicode glyphs. | |
101 | ||
3f5ac303 | 102 | * `$RUNTIME_DIRECTORY` — various tools use this variable to locate the |
e7b86e48 ZJS |
103 | appropriate path under `/run/`. This variable is also set by the manager when |
104 | `RuntimeDirectory=` is used, see systemd.exec(5). | |
3f5ac303 | 105 | |
42f3b2f9 | 106 | * `$SYSTEMD_CRYPT_PREFIX` — if set configures the hash method prefix to use for |
e7b86e48 ZJS |
107 | UNIX `crypt()` when generating passwords. By default the system's "preferred |
108 | method" is used, but this can be overridden with this environment variable. | |
109 | Takes a prefix such as `$6$` or `$y$`. (Note that this is only honoured on | |
110 | systems built with libxcrypt and is ignored on systems using glibc's | |
111 | original, internal `crypt()` implementation.) | |
42f3b2f9 | 112 | |
54dcf847 | 113 | * `$SYSTEMD_SECCOMP=0` — if set, seccomp filters will not be enforced, even if |
ce8f6d47 LP |
114 | support for it is compiled in and available in the kernel. |
115 | ||
116 | * `$SYSTEMD_LOG_SECCOMP=1` — if set, system calls blocked by seccomp filtering, | |
e7b86e48 ZJS |
117 | for example in `systemd-nspawn`, will be logged to the audit log, if the |
118 | kernel supports this. | |
ce8f6d47 | 119 | |
7c7a9138 DDM |
120 | * `$SYSTEMD_ENABLE_LOG_CONTEXT` — if set, extra fields will always be logged to |
121 | the journal instead of only when logging in debug mode. | |
122 | ||
e7b86e48 | 123 | `systemctl`: |
4549fcdb | 124 | |
8f1a581e | 125 | * `$SYSTEMCTL_FORCE_BUS=1` — if set, do not connect to PID 1's private D-Bus |
4549fcdb LP |
126 | listener, and instead always connect through the dbus-daemon D-bus broker. |
127 | ||
128 | * `$SYSTEMCTL_INSTALL_CLIENT_SIDE=1` — if set, enable or disable unit files on | |
129 | the client side, instead of asking PID 1 to do this. | |
130 | ||
e7b86e48 | 131 | * `$SYSTEMCTL_SKIP_SYSV=1` — if set, do not call SysV compatibility hooks. |
4549fcdb | 132 | |
e7b86e48 | 133 | `systemd-nspawn`: |
4549fcdb | 134 | |
e7b86e48 ZJS |
135 | * `$SYSTEMD_NSPAWN_UNIFIED_HIERARCHY=1` — if set, force `systemd-nspawn` into |
136 | unified cgroup hierarchy mode. | |
4549fcdb | 137 | |
e7b86e48 ZJS |
138 | * `$SYSTEMD_NSPAWN_API_VFS_WRITABLE=1` — if set, make `/sys/`, `/proc/sys/`, |
139 | and friends writable in the container. If set to "network", leave only | |
140 | `/proc/sys/net/` writable. | |
4549fcdb LP |
141 | |
142 | * `$SYSTEMD_NSPAWN_CONTAINER_SERVICE=…` — override the "service" name nspawn | |
143 | uses to register with machined. If unset defaults to "nspawn", but with this | |
144 | variable may be set to any other value. | |
145 | ||
146 | * `$SYSTEMD_NSPAWN_USE_CGNS=0` — if set, do not use cgroup namespacing, even if | |
147 | it is available. | |
148 | ||
149 | * `$SYSTEMD_NSPAWN_LOCK=0` — if set, do not lock container images when running. | |
150 | ||
e7b86e48 | 151 | * `$SYSTEMD_NSPAWN_TMPFS_TMP=0` — if set, do not overmount `/tmp/` in the |
1099ceeb LP |
152 | container with a tmpfs, but leave the directory from the image in place. |
153 | ||
4a4654e0 LP |
154 | * `$SYSTEMD_SUPPRESS_SYNC=1` — if set, all disk synchronization syscalls are |
155 | blocked to the container payload (e.g. `sync()`, `fsync()`, `syncfs()`, …) | |
156 | and the `O_SYNC`/`O_DSYNC` flags are made unavailable to `open()` and | |
157 | friends. This is equivalent to passing `--suppress-sync=yes` on the | |
158 | `systemd-nspawn` command line. | |
159 | ||
e7b86e48 | 160 | `systemd-logind`: |
4549fcdb LP |
161 | |
162 | * `$SYSTEMD_BYPASS_HIBERNATION_MEMORY_CHECK=1` — if set, report that | |
163 | hibernation is available even if the swap devices do not provide enough room | |
164 | for it. | |
94fa1497 | 165 | |
e7b86e48 ZJS |
166 | * `$SYSTEMD_REBOOT_TO_FIRMWARE_SETUP` — if set, overrides `systemd-logind`'s |
167 | built-in EFI logic of requesting a reboot into the firmware. Takes a boolean. | |
168 | If set to false, the functionality is turned off entirely. If set to true, | |
169 | instead of requesting a reboot into the firmware setup UI through EFI a file, | |
170 | `/run/systemd/reboot-to-firmware-setup` is created whenever this is | |
e86c7a3a LP |
171 | requested. This file may be checked for by services run during system |
172 | shutdown in order to request the appropriate operation from the firmware in | |
173 | an alternative fashion. | |
174 | ||
175 | * `$SYSTEMD_REBOOT_TO_BOOT_LOADER_MENU` — similar to the above, allows | |
e7b86e48 ZJS |
176 | overriding of `systemd-logind`'s built-in EFI logic of requesting a reboot |
177 | into the boot loader menu. Takes a boolean. If set to false, the | |
178 | functionality is turned off entirely. If set to true, instead of requesting a | |
179 | reboot into the boot loader menu through EFI, the file | |
180 | `/run/systemd/reboot-to-boot-loader-menu` is created whenever this is | |
181 | requested. The file contains the requested boot loader menu timeout in µs, | |
182 | formatted in ASCII decimals, or zero in case no timeout is requested. This | |
183 | file may be checked for by services run during system shutdown in order to | |
184 | request the appropriate operation from the boot loader in an alternative | |
185 | fashion. | |
e86c7a3a LP |
186 | |
187 | * `$SYSTEMD_REBOOT_TO_BOOT_LOADER_ENTRY` — similar to the above, allows | |
e7b86e48 ZJS |
188 | overriding of `systemd-logind`'s built-in EFI logic of requesting a reboot |
189 | into a specific boot loader entry. Takes a boolean. If set to false, the | |
190 | functionality is turned off entirely. If set to true, instead of requesting a | |
191 | reboot into a specific boot loader entry through EFI, the file | |
e86c7a3a LP |
192 | `/run/systemd/reboot-to-boot-loader-entry` is created whenever this is |
193 | requested. The file contains the requested boot loader entry identifier. This | |
194 | file may be checked for by services run during system shutdown in order to | |
195 | request the appropriate operation from the boot loader in an alternative | |
5c90c67a | 196 | fashion. Note that by default only boot loader entries which follow the |
db811444 ZJS |
197 | [Boot Loader Specification](https://uapi-group.org/specifications/specs/boot_loader_specification) |
198 | and are placed in the ESP or the Extended Boot Loader partition may be | |
199 | selected this way. However, if a directory `/run/boot-loader-entries/` | |
200 | exists, the entries are loaded from there instead. The directory should | |
201 | contain the usual directory hierarchy mandated by the Boot Loader | |
202 | Specification, i.e. the entry drop-ins should be placed in | |
e86c7a3a LP |
203 | `/run/boot-loader-entries/loader/entries/*.conf`, and the files referenced by |
204 | the drop-ins (including the kernels and initrds) somewhere else below | |
205 | `/run/boot-loader-entries/`. Note that all these files may be (and are | |
e7b86e48 | 206 | supposed to be) symlinks. `systemd-logind` will load these files on-demand, |
e86c7a3a LP |
207 | these files can hence be updated (ideally atomically) whenever the boot |
208 | loader configuration changes. A foreign boot loader installer script should | |
209 | hence synthesize drop-in snippets and symlinks for all boot entries at boot | |
e7b86e48 ZJS |
210 | or whenever they change if it wants to integrate with `systemd-logind`'s |
211 | APIs. | |
e86c7a3a | 212 | |
a7910612 | 213 | `systemd-udevd` and sd-device library: |
679dab6a | 214 | |
54dcf847 | 215 | * `$NET_NAMING_SCHEME=` — if set, takes a network naming scheme (i.e. one of |
679dab6a | 216 | "v238", "v239", "v240"…, or the special value "latest") as parameter. If |
e7b86e48 ZJS |
217 | specified udev's `net_id` builtin will follow the specified naming scheme |
218 | when determining stable network interface names. This may be used to revert | |
219 | to naming schemes of older udev versions, in order to provide more stable | |
220 | naming across updates. This environment variable takes precedence over the | |
221 | kernel command line option `net.naming-scheme=`, except if the value is | |
222 | prefixed with `:` in which case the kernel command line option takes | |
223 | precedence, if it is specified as well. | |
679dab6a | 224 | |
a7910612 LP |
225 | * `$SYSTEMD_DEVICE_VERIFY_SYSFS` — if set to "0", disables verification that |
226 | devices sysfs path are actually backed by sysfs. Relaxing this verification | |
227 | is useful for testing purposes. | |
228 | ||
e7b86e48 | 229 | `nss-systemd`: |
dba1bd43 LP |
230 | |
231 | * `$SYSTEMD_NSS_BYPASS_SYNTHETIC=1` — if set, `nss-systemd` won't synthesize | |
232 | user/group records for the `root` and `nobody` users if they are missing from | |
233 | `/etc/passwd`. | |
234 | ||
235 | * `$SYSTEMD_NSS_DYNAMIC_BYPASS=1` — if set, `nss-systemd` won't return | |
236 | user/group records for dynamically registered service users (i.e. users | |
237 | registered through `DynamicUser=1`). | |
238 | ||
e7b86e48 | 239 | `systemd-timedated`: |
41d0da0f YW |
240 | |
241 | * `$SYSTEMD_TIMEDATED_NTP_SERVICES=…` — colon-separated list of unit names of | |
242 | NTP client services. If set, `timedatectl set-ntp on` enables and starts the | |
243 | first existing unit listed in the environment variable, and | |
244 | `timedatectl set-ntp off` disables and stops all listed units. | |
39922217 | 245 | |
e7b86e48 | 246 | `systemd-sulogin-shell`: |
33eb44fe AH |
247 | |
248 | * `$SYSTEMD_SULOGIN_FORCE=1` — This skips asking for the root password if the | |
249 | root password is not available (such as when the root account is locked). | |
250 | See `sulogin(8)` for more details. | |
251 | ||
e7b86e48 | 252 | `bootctl` and other tools that access the EFI System Partition (ESP): |
8cbb7d87 LP |
253 | |
254 | * `$SYSTEMD_RELAX_ESP_CHECKS=1` — if set, the ESP validation checks are | |
255 | relaxed. Specifically, validation checks that ensure the specified ESP path | |
256 | is a FAT file system are turned off, as are checks that the path is located | |
257 | on a GPT partition with the correct type UUID. | |
258 | ||
cc7a0bfa LP |
259 | * `$SYSTEMD_ESP_PATH=…` — override the path to the EFI System Partition. This |
260 | may be used to override ESP path auto detection, and redirect any accesses to | |
e7b86e48 ZJS |
261 | the ESP to the specified directory. Note that unlike with `bootctl`'s |
262 | `--path=` switch only very superficial validation of the specified path is | |
263 | done when this environment variable is used. | |
cc7a0bfa | 264 | |
2e76ca79 LN |
265 | * `$KERNEL_INSTALL_CONF_ROOT=…` — override the built in default configuration |
266 | directory /etc/kernel/ to read files like entry-token and install.conf from. | |
267 | ||
e7b86e48 | 268 | `systemd` itself: |
39922217 LP |
269 | |
270 | * `$SYSTEMD_ACTIVATION_UNIT` — set for all NSS and PAM module invocations that | |
271 | are done by the service manager on behalf of a specific unit, in child | |
272 | processes that are later (after execve()) going to become unit | |
273 | processes. Contains the full unit name (e.g. "foobar.service"). NSS and PAM | |
274 | modules can use this information to determine in which context and on whose | |
275 | behalf they are being called, which may be useful to avoid deadlocks, for | |
276 | example to bypass IPC calls to the very service that is about to be | |
277 | started. Note that NSS and PAM modules should be careful to only rely on this | |
278 | data when invoked privileged, or possibly only when getppid() returns 1, as | |
279 | setting environment variables is of course possible in any even unprivileged | |
280 | contexts. | |
281 | ||
282 | * `$SYSTEMD_ACTIVATION_SCOPE` — closely related to `$SYSTEMD_ACTIVATION_UNIT`, | |
283 | it is either set to `system` or `user` depending on whether the NSS/PAM | |
284 | module is called by systemd in `--system` or `--user` mode. | |
59f13dd6 | 285 | |
88e4bfa6 MS |
286 | * `$SYSTEMD_SUPPORT_DEVICE`, `$SYSTEMD_SUPPORT_MOUNT`, `$SYSTEMD_SUPPORT_SWAP` - |
287 | can be set to `0` to mark respective unit type as unsupported. Generally, | |
288 | having less units saves system resources so these options might be useful | |
289 | for cases where we don't need to track given unit type, e.g. `--user` manager | |
290 | often doesn't need to deal with device or swap units because they are | |
291 | handled by the `--system` manager (PID 1). Note that setting certain unit | |
292 | type as unsupported may not prevent loading some units of that type if they | |
293 | are referenced by other units of another supported type. | |
294 | ||
24a4542c LB |
295 | * `$SYSTEMD_DEFAULT_MOUNT_RATE_LIMIT_BURST` — can be set to override the mount |
296 | units burst rate limit for parsing `/proc/self/mountinfo`. On a system with | |
297 | few resources but many mounts the rate limit may be hit, which will cause the | |
298 | processing of mount units to stall. The burst limit may be adjusted when the | |
299 | default is not appropriate for a given system. Defaults to `5`, accepts | |
300 | positive integers. | |
301 | ||
e7b86e48 | 302 | `systemd-remount-fs`: |
59f13dd6 | 303 | |
d238709c | 304 | * `$SYSTEMD_REMOUNT_ROOT_RW=1` — if set and no entry for the root directory |
e7b86e48 | 305 | exists in `/etc/fstab` (this file always takes precedence), then the root |
59f13dd6 | 306 | directory is remounted writable. This is primarily used by |
e7b86e48 | 307 | `systemd-gpt-auto-generator` to ensure the root partition is mounted writable |
59f13dd6 | 308 | in accordance to the GPT partition flags. |
a7d9fccd | 309 | |
e7b86e48 | 310 | `systemd-firstboot` and `localectl`: |
a7d9fccd | 311 | |
54dcf847 | 312 | * `$SYSTEMD_LIST_NON_UTF8_LOCALES=1` — if set, non-UTF-8 locales are listed among |
a7d9fccd LP |
313 | the installed ones. By default non-UTF-8 locales are suppressed from the |
314 | selection, since we are living in the 21st century. | |
7a87fb61 | 315 | |
d8962609 JM |
316 | `systemd-resolved`: |
317 | ||
318 | * `$SYSTEMD_RESOLVED_SYNTHESIZE_HOSTNAME` — if set to "0", `systemd-resolved` | |
319 | won't synthesize system hostname on both regular and reverse lookups. | |
320 | ||
e7b86e48 | 321 | `systemd-sysext`: |
7a87fb61 | 322 | |
54dcf847 | 323 | * `$SYSTEMD_SYSEXT_HIERARCHIES` — this variable may be used to override which |
e7b86e48 ZJS |
324 | hierarchies are managed by `systemd-sysext`. By default only `/usr/` and |
325 | `/opt/` are managed, and directories may be added or removed to that list by | |
326 | setting this environment variable to a colon-separated list of absolute | |
327 | paths. Only "real" file systems and directories that only contain "real" file | |
328 | systems as submounts should be used. Do not specify API file systems such as | |
329 | `/proc/` or `/sys/` here, or hierarchies that have them as submounts. In | |
1f4f1666 | 330 | particular, do not specify the root directory `/` here. Similarly, |
331 | `$SYSTEMD_CONFEXT_HIERARCHIES` works for confext images and supports the | |
332 | systemd-confext multi-call functionality of sysext. | |
4368c60c | 333 | |
e7b86e48 | 334 | `systemd-tmpfiles`: |
4368c60c | 335 | |
54dcf847 | 336 | * `$SYSTEMD_TMPFILES_FORCE_SUBVOL` — if unset, `v`/`q`/`Q` lines will create |
e7b86e48 ZJS |
337 | subvolumes only if the OS itself is installed into a subvolume. If set to `1` |
338 | (or another value interpreted as true), these lines will always create | |
339 | subvolumes if the backing filesystem supports them. If set to `0`, these | |
340 | lines will always create directories. | |
07dc08c2 | 341 | |
3fa8a114 JSMR |
342 | `systemd-sysusers` |
343 | ||
344 | * `SOURCE_DATE_EPOCH` — if unset, the field of the date of last password change | |
345 | in `/etc/shadow` will be the number of days from Jan 1, 1970 00:00 UTC until | |
1a127aa0 | 346 | today. If `$SOURCE_DATE_EPOCH` is set to a valid UNIX epoch value in seconds, |
3fa8a114 JSMR |
347 | then the field will be the number of days until that time instead. This is to |
348 | support creating bit-by-bit reproducible system images by choosing a | |
349 | reproducible value for the field of the date of last password change in | |
350 | `/etc/shadow`. See: https://reproducible-builds.org/specs/source-date-epoch/ | |
351 | ||
07dc08c2 ZJS |
352 | `systemd-sysv-generator`: |
353 | ||
354 | * `$SYSTEMD_SYSVINIT_PATH` — Controls where `systemd-sysv-generator` looks for | |
355 | SysV init scripts. | |
356 | ||
357 | * `$SYSTEMD_SYSVRCND_PATH` — Controls where `systemd-sysv-generator` looks for | |
358 | SysV init script runlevel link farms. | |
48eb2af6 | 359 | |
f0cb09bb ZJS |
360 | systemd tests: |
361 | ||
362 | * `$SYSTEMD_TEST_DATA` — override the location of test data. This is useful if | |
363 | a test executable is moved to an arbitrary location. | |
364 | ||
365 | * `$SYSTEMD_TEST_NSS_BUFSIZE` — size of scratch buffers for "reentrant" | |
366 | functions exported by the nss modules. | |
367 | ||
48eb2af6 ZJS |
368 | fuzzers: |
369 | ||
370 | * `$SYSTEMD_FUZZ_OUTPUT` — A boolean that specifies whether to write output to | |
371 | stdout. Setting to true is useful in manual invocations, since all output is | |
372 | suppressed by default. | |
373 | ||
374 | * `$SYSTEMD_FUZZ_RUNS` — The number of times execution should be repeated in | |
375 | manual invocations. | |
376 | ||
f223fd6a | 377 | Note that it may be also useful to set `$SYSTEMD_LOG_LEVEL`, since all logging |
48eb2af6 | 378 | is suppressed by default. |
23851640 | 379 | |
54dcf847 | 380 | `systemd-importd`: |
23851640 | 381 | |
54dcf847 | 382 | * `$SYSTEMD_IMPORT_BTRFS_SUBVOL` — takes a boolean, which controls whether to |
23851640 LP |
383 | prefer creating btrfs subvolumes over plain directories for machine |
384 | images. Has no effect on non-btrfs file systems where subvolumes are not | |
385 | available anyway. If not set, defaults to true. | |
386 | ||
54dcf847 | 387 | * `$SYSTEMD_IMPORT_BTRFS_QUOTA` — takes a boolean, which controls whether to set |
23851640 LP |
388 | up quota automatically for created btrfs subvolumes for machine images. If |
389 | not set, defaults to true. Has no effect if machines are placed in regular | |
390 | directories, because btrfs subvolumes are not supported or disabled. If | |
391 | enabled, the quota group of the subvolume is automatically added to a | |
392 | combined quota group for all such machine subvolumes. | |
393 | ||
54dcf847 | 394 | * `$SYSTEMD_IMPORT_SYNC` — takes a boolean, which controls whether to |
23851640 LP |
395 | synchronize images to disk after installing them, before completing the |
396 | operation. If not set, defaults to true. If disabled installation of images | |
397 | will be quicker, but not as safe. | |
54dcf847 LP |
398 | |
399 | `systemd-dissect`, `systemd-nspawn` and all other tools that may operate on | |
400 | disk images with `--image=` or similar: | |
401 | ||
402 | * `$SYSTEMD_DISSECT_VERITY_SIDECAR` — takes a boolean, which controls whether to | |
403 | load "sidecar" Verity metadata files. If enabled (which is the default), | |
404 | whenever a disk image is used, a set of files with the `.roothash`, | |
405 | `.usrhash`, `.roothash.p7s`, `.usrhash.p7s`, `.verity` suffixes are searched | |
406 | adjacent to disk image file, containing the Verity root hashes, their | |
407 | signatures or the Verity data itself. If disabled this automatic discovery of | |
408 | Verity metadata files is turned off. | |
409 | ||
410 | * `$SYSTEMD_DISSECT_VERITY_EMBEDDED` — takes a boolean, which controls whether | |
411 | to load the embedded Verity signature data. If enabled (which is the | |
412 | default), Verity root hash information and a suitable signature is | |
413 | automatically acquired from a signature partition, following the | |
db811444 | 414 | [Discoverable Partitions Specification](https://uapi-group.org/specifications/specs/discoverable_partitions_specification). |
5c90c67a BF |
415 | If disabled any such partition is ignored. Note that this only disables |
416 | discovery of the root hash and its signature, the Verity data partition | |
417 | itself is still searched in the GPT image. | |
54dcf847 LP |
418 | |
419 | * `$SYSTEMD_DISSECT_VERITY_SIGNATURE` — takes a boolean, which controls whether | |
420 | to validate the signature of the Verity root hash if available. If enabled | |
421 | (which is the default), the signature of suitable disk images is validated | |
422 | against any of the certificates in `/etc/verity.d/*.crt` (and similar | |
ba669952 | 423 | directories in `/usr/lib/`, `/run`, …) or passed to the kernel for validation |
54dcf847 | 424 | against its built-in certificates. |
ccd25f41 | 425 | |
2b660510 YW |
426 | * `$SYSTEMD_DISSECT_VERITY_TIMEOUT_SEC=sec` — takes a timespan, which controls |
427 | the timeout waiting for the image to be configured. Defaults to 100 msec. | |
428 | ||
80ce8580 LP |
429 | * `$SYSTEMD_DISSECT_FILE_SYSTEMS=` — takes a colon-separated list of file |
430 | systems that may be mounted for automatically dissected disk images. If not | |
431 | specified defaults to something like: `ext4:btrfs:xfs:vfat:erofs:squashfs` | |
432 | ||
e8c7c4d9 | 433 | * `$SYSTEMD_LOOP_DIRECT_IO` – takes a boolean, which controls whether to enable |
1a127aa0 | 434 | `LO_FLAGS_DIRECT_IO` (i.e. direct IO + asynchronous IO) on loopback block |
e8c7c4d9 LP |
435 | devices when opening them. Defaults to on, set this to "0" to disable this |
436 | feature. | |
437 | ||
ccd25f41 LP |
438 | `systemd-cryptsetup`: |
439 | ||
440 | * `$SYSTEMD_CRYPTSETUP_USE_TOKEN_MODULE` – takes a boolean, which controls | |
441 | whether to use the libcryptsetup "token" plugin module logic even when | |
442 | activating via FIDO2, PKCS#11, TPM2, i.e. mechanisms natively supported by | |
443 | `systemd-cryptsetup`. Defaults to enabled. | |
c04358ce LP |
444 | |
445 | Various tools that read passwords from the TTY, such as `systemd-cryptenroll` | |
446 | and `homectl`: | |
447 | ||
448 | * `$PASSWORD` — takes a string: the literal password to use. If this | |
449 | environment variable is set it is used as password instead of prompting the | |
450 | user interactively. This exists primarily for debugging and testing | |
451 | purposes. Do not use this for production code paths, since environment | |
452 | variables are typically inherited down the process tree without restrictions | |
453 | and should thus not be used for secrets. | |
454 | ||
455 | * `$NEWPASSWORD` — similar to `$PASSWORD` above, but is used when both a | |
456 | current and a future password are required, for example if the password is to | |
457 | be changed. In that case `$PASSWORD` shall carry the current (i.e. old) | |
458 | password and `$NEWPASSWORD` the new. | |
67302b38 LP |
459 | |
460 | `systemd-homed`: | |
461 | ||
462 | * `$SYSTEMD_HOME_ROOT` – defines an absolute path where to look for home | |
463 | directories/images. When unspecified defaults to `/home/`. This is useful for | |
464 | debugging purposes in order to run a secondary `systemd-homed` instance that | |
465 | operates on a different directory where home directories/images are placed. | |
466 | ||
467 | * `$SYSTEMD_HOME_RECORD_DIR` – defines an absolute path where to look for | |
468 | fixated home records kept on the host. When unspecified defaults to | |
469 | `/var/lib/systemd/home/`. Similar to `$SYSTEMD_HOME_ROOT` this is useful for | |
470 | debugging purposes, in order to run a secondary `systemd-homed` instance that | |
471 | operates on a record database entirely separate from the host's. | |
472 | ||
473 | * `$SYSTEMD_HOME_DEBUG_SUFFIX` – takes a short string that is suffixed to | |
474 | `systemd-homed`'s D-Bus and Varlink service names/sockets. This is also | |
a6f44d61 | 475 | understood by `homectl`. This too is useful for running an additional copy of |
67302b38 LP |
476 | `systemd-homed` that doesn't interfere with the host's main one. |
477 | ||
478 | * `$SYSTEMD_HOMEWORK_PATH` – configures the path to the `systemd-homework` | |
479 | binary to invoke. If not specified defaults to | |
480 | `/usr/lib/systemd/systemd-homework`. | |
481 | ||
482 | Combining these four environment variables is pretty useful when | |
483 | debugging/developing `systemd-homed`: | |
484 | ```sh | |
485 | SYSTEMD_HOME_DEBUG_SUFFIX=foo \ | |
486 | SYSTEMD_HOMEWORK_PATH=/home/lennart/projects/systemd/build/systemd-homework \ | |
487 | SYSTEMD_HOME_ROOT=/home.foo/ \ | |
488 | SYSTEMD_HOME_RECORD_DIR=/var/lib/systemd/home.foo/ \ | |
489 | /home/lennart/projects/systemd/build/systemd-homed | |
490 | ``` | |
db42f011 LP |
491 | |
492 | * `$SYSTEMD_HOME_MOUNT_OPTIONS_BTRFS`, `$SYSTEMD_HOME_MOUNT_OPTIONS_EXT4`, | |
493 | `$SYSTEMD_HOME_MOUNT_OPTIONS_XFS` – configure the default mount options to | |
494 | use for LUKS home directories, overriding the built-in default mount | |
495 | options. There's one variable for each of the supported file systems for the | |
496 | LUKS home directory backend. | |
a2a9d541 | 497 | |
8f30c00c AD |
498 | * `$SYSTEMD_HOME_MKFS_OPTIONS_BTRFS`, `$SYSTEMD_HOME_MKFS_OPTIONS_EXT4`, |
499 | `$SYSTEMD_HOME_MKFS_OPTIONS_XFS` – configure additional arguments to use for | |
500 | `mkfs` when formatting LUKS home directories. There's one variable for each | |
501 | of the supported file systems for the LUKS home directory backend. | |
502 | ||
a2a9d541 DDM |
503 | `kernel-install`: |
504 | ||
505 | * `$KERNEL_INSTALL_BYPASS` – If set to "1", execution of kernel-install is skipped | |
506 | when kernel-install is invoked. This can be useful if kernel-install is invoked | |
507 | unconditionally as a child process by another tool, such as package managers | |
508 | running kernel-install in a postinstall script. | |
61297656 DDM |
509 | |
510 | `systemd-journald`: | |
511 | ||
6337be0a | 512 | * `$SYSTEMD_JOURNAL_COMPACT` – Takes a boolean. If enabled, journal files are written |
61297656 DDM |
513 | in a more compact format that reduces the amount of disk space required by the |
514 | journal. Note that journal files in compact mode are limited to 4G to allow use of | |
515 | 32-bit offsets. Enabled by default. | |
6337be0a | 516 | |
1f06ea74 YW |
517 | * `$SYSTEMD_JOURNAL_COMPRESS` – Takes a boolean, or one of the compression |
518 | algorithms "XZ", "LZ4", and "ZSTD". If enabled, the default compression | |
519 | algorithm set at compile time will be used when opening a new journal file. | |
520 | If disabled, the journal file compression will be disabled. Note that the | |
521 | compression mode of existing journal files are not changed. To make the | |
522 | specified algorithm takes an effect immediately, you need to explicitly run | |
523 | `journalctl --rotate`. | |
524 | ||
6c51b49c | 525 | `systemd-pcrphase`, `systemd-cryptsetup`: |
6337be0a | 526 | |
6c51b49c LP |
527 | * `$SYSTEMD_FORCE_MEASURE=1` — If set, force measuring of resources (which are |
528 | marked for measurement) even if not booted on a kernel equipped with | |
529 | systemd-stub. Normally, requested measurement of resources is conditionalized | |
530 | on kernels that have booted with `systemd-stub`. With this environment | |
531 | variable the test for that my be bypassed, for testing purposes. | |
4b8ce14f DDM |
532 | |
533 | `systemd-repart`: | |
534 | ||
535 | * `$SYSTEMD_REPART_MKFS_OPTIONS_<FSTYPE>` – configure additional arguments to use for | |
536 | `mkfs` when formatting partition file systems. There's one variable for each | |
537 | of the supported file systems. |