it is either set to `system` or `user` depending on whether the NSS/PAM
module is called by systemd in `--system` or `--user` mode.
+* `$SYSTEMD_SUPPORT_DEVICE`, `$SYSTEMD_SUPPORT_MOUNT`, `$SYSTEMD_SUPPORT_SWAP` -
+ can be set to `0` to mark respective unit type as unsupported. Generally,
+ having less units saves system resources so these options might be useful
+ for cases where we don't need to track given unit type, e.g. `--user` manager
+ often doesn't need to deal with device or swap units because they are
+ handled by the `--system` manager (PID 1). Note that setting certain unit
+ type as unsupported may not prevent loading some units of that type if they
+ are referenced by other units of another supported type.
+
`systemd-remount-fs`:
* `$SYSTEMD_REMOUNT_ROOT_RW=1` — if set and no entry for the root directory
#include "dbus-unit.h"
#include "dbus.h"
#include "dropin.h"
+#include "env-util.h"
#include "escape.h"
#include "execute.h"
#include "fd-util.h"
}
bool unit_type_supported(UnitType t) {
+ static int8_t cache[_UNIT_TYPE_MAX] = {}; /* -1: disabled, 1: enabled: 0: don't know */
+ int r;
+
if (_unlikely_(t < 0))
return false;
if (_unlikely_(t >= _UNIT_TYPE_MAX))
return false;
+ if (cache[t] == 0) {
+ char *e;
+
+ e = strjoina("SYSTEMD_SUPPORT_", unit_type_to_string(t));
+
+ r = getenv_bool(ascii_strupper(e));
+ if (r < 0 && r != -ENXIO)
+ log_debug_errno(r, "Failed to parse $%s, ignoring: %m", e);
+
+ cache[t] = r == 0 ? -1 : 1;
+ }
+ if (cache[t] < 0)
+ return false;
+
if (!unit_vtable[t]->supported)
return true;