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core: add possibility to not track certain unit types

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Michal Sekletar 2022-09-07 17:37:34 +02:00 committed by Yu Watanabe
parent 80d95fcd6e
commit 88e4bfa62b
2 changed files with 27 additions and 0 deletions
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9
docs/ENVIRONMENT.md
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@ -274,6 +274,15 @@ All tools:
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

18
src/core/unit.c
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@ -22,6 +22,7 @@
#include "dbus-unit.h"
#include "dbus.h"
#include "dropin.h"
#include "env-util.h"
#include "escape.h"
#include "execute.h"
#include "fd-util.h"
@ -4781,11 +4782,28 @@ int unit_setup_dynamic_creds(Unit *u) {
}
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;