All tools:
+* `$SYSTEMD_OFFLINE=[0|1]` — if set to `1`, then `systemctl` will
+ refrain from talking to PID 1; this has the same effect as the historical
+ detection of `chroot()`. Setting this variable to `0` instead has a similar
+ effect as `SYSTEMD_IGNORE_CHROOT=1`; i.e. tools will try to
+ communicate with PID 1 even if a `chroot()` environment is detected.
+ You almost certainly want to set this to `1` if you maintain a package build system
+ or similar and are trying to use a modern container system and not plain
+ `chroot()`.
+
* `$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.)
+ `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; turning most operations such
+ as `start` into no-ops. If that's what's explicitly desired, you might
+ consider setting `SYSTEMD_OFFLINE=1`.
* `$SD_EVENT_PROFILE_DELAYS=1` — if set, the sd-event event loop implementation
will print latency information at runtime.
* `$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`.