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