Add remain:yes option for run/task oneshot commands

Similar to systemd's RemainAfterExit=yes.  Prevents the task from
re-running on runlevel re-entry and ensures the post: script runs
when explicitly stopped or when leaving valid runlevels.

Useful for tasks that set up persistent state like firewall rules:

    task [2345] remain:yes \
         post:/usr/sbin/teardown-firewall \
         /usr/sbin/setup-firewall -- Firewall setup

Not supported for bootstrap-only tasks (runlevel S only) since these
are deleted immediately after completion.

Author: aanderse

doc/config/service-opts.md

@@ -69,6 +69,11 @@ confines of that the following options are available:
   * `respawn` -- bypasses the `restart` mechanism completely, allows
     endless restarts.  Useful in many use-cases, but not what `service`
     was originally designed for so not the default behavior
+  * `remain:yes` -- for `run` and `task` only.  Prevents the task from
+    re-running on runlevel re-entry and ensures the `post:` script runs
+    when the task is explicitly stopped or leaves its valid runlevels.
+    Similar to systemd's `RemainAfterExit=yes`.  See [Task and Run](task-and-run.md)
+    for more details
   * `oncrash:reboot` -- when all retries have failed, and the service
     has *crashed*, if this option is set the system is rebooted
   * `oncrash:script` -- similarly, but instead of rebooting, call the

doc/config/task-and-run.md

@@ -44,3 +44,44 @@ redirects can be used:
 
 Please note, `;`, `&&`, `||`, and similar are *not supported*.  Any
 non-trivial constructs are better placed in a separate shell script.
+
+
+remain:yes
+----------
+
+By default, a `run` or `task` will re-run each time its runlevel is
+entered, and its `post:` script does not run on completion.
+
+With `remain:yes`, the task runs once and does not re-run on runlevel
+re-entry:
+
+    task [2345] remain:yes /usr/sbin/setup-firewall -- Firewall setup
+
+This has the following effects:
+
+  * The task does not re-run on runlevel re-entry
+  * The `post:` script runs when:
+    - The task is explicitly stopped (`initctl stop NAME`)
+    - The task leaves its valid runlevels (e.g., runlevel change)
+
+This is useful for tasks that set up persistent state where:
+
+  * Cleanup should only happen on explicit stop or when leaving valid runlevels
+  * The setup should not be re-run on every runlevel entry
+
+**Example:** Setting up firewall rules with cleanup on shutdown:
+
+```
+task [2345] remain:yes \
+     post:/usr/sbin/teardown-firewall \
+     /usr/sbin/setup-firewall -- Firewall setup
+```
+
+The firewall rules are created once.  The `post:` script runs when
+entering runlevel 0 (halt) or 6 (reboot), or on explicit stop.
+
+> [!NOTE]
+> The `remain:yes` option is not supported for bootstrap-only tasks
+> (tasks with only runlevel S).  Bootstrap tasks are deleted immediately
+> after completion, and their `post:` scripts never run.  A warning is
+> logged if `remain:yes` is used on such tasks.

man/finit.conf.5

@@ -398,6 +398,20 @@ mechanism completely, allows endless restarts.  Useful in many
 use-cases, but not what
 .Cm service
 was originally designed for so not the default behavior.
+.It Cm remain:yes
+for
+.Cm run
+and
+.Cm task
+only.  Prevents the task from re-running on runlevel re-entry and
+ensures the
+.Cm post:
+script runs when the task is explicitly stopped or leaves its valid
+runlevels.  Similar to systemd's
+.Cm RemainAfterExit=yes .
+.Pp
+.Sy Note:
+not supported for bootstrap-only tasks (runlevels [S] only).
 .It Cm oncrash:reboot
 when all retries have failed, and the service
 has

src/service.c

@@ -1798,7 +1798,7 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 	char *dev = NULL;
 	int respawn = 0;
 	int levels = 0;
-	int forking = 0, manual = 0, nowarn = 0;
+	int forking = 0, manual = 0, remain = 0, nowarn = 0;
 	int restart_max = SVC_RESPAWN_MAX;
 	int restart_tmo = 0;
 	unsigned oncrash_action = SVC_ONCRASH_IGNORE;
@@ -1866,6 +1866,8 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 			forking = 1;
 		else if (MATCH_CMD(cmd, "manual:yes", arg))
 			manual = 1;
+		else if (MATCH_CMD(cmd, "remain:yes", arg))
+			remain = 1;
 		else if (MATCH_CMD(cmd, "restart:", arg)) {
 			if (MATCH_CMD(arg, "always", arg))
 				restart_max = -1;
@@ -2171,6 +2173,18 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 		memset(svc->ifstmt, 0, sizeof(svc->ifstmt));
 	svc->manual  = manual;
 	svc->nowarn  = nowarn;
+
+	/*
+	 * remain:yes is not supported for bootstrap-only tasks.  These
+	 * tasks are deleted immediately after completion and their post:
+	 * scripts never run.  This is by design.
+	 */
+	if (remain && svc_is_runtask(svc) && !ISOTHER(levels, INIT_LEVEL)) {
+		logit(LOG_WARNING, "%s: remain:yes ignored for bootstrap-only tasks",
+		      svc_ident(svc, NULL, 0));
+		remain = 0;
+	}
+	svc->remain  = remain;
 	svc->respawn = respawn;
 	svc->forking = forking;
 	svc->restart_max = restart_max;
@@ -2876,9 +2890,16 @@ int service_step(svc_t *svc)
 		break;
 
 	case SVC_DONE_STATE:
-		if (svc_is_changed(svc))
+		/* Remain tasks: always run post script when stopped, even if config changed */
+		if (svc_is_runtask(svc) && svc_is_remain(svc) && svc_is_stopped(svc)) {
+			if (svc_has_post(svc)) {
+				svc_set_state(svc, SVC_TEARDOWN_STATE);
+				service_post_script(svc);
+			} else
+				svc_set_state(svc, SVC_HALTED_STATE);
+		} else if (svc_is_changed(svc))
 			svc_set_state(svc, SVC_HALTED_STATE);
-		if (svc_is_runtask(svc) && svc_is_manual(svc) && enabled)
+		else if (svc_is_runtask(svc) && svc_is_manual(svc) && enabled)
 			svc_set_state(svc, SVC_WAITING_STATE);
 		break;
 
@@ -3180,6 +3201,18 @@ void service_runtask_clean(void)
 		if (!svc_is_runtask(svc))
 			continue;
 
+		/* Remain tasks stay in DONE state if still valid in new runlevel */
+		if (svc_is_remain(svc) && svc->state == SVC_DONE_STATE) {
+			if (svc_in_runlevel(svc, runlevel) && !svc_is_changed(svc))
+				continue;	/* Keep once flag, stay in DONE */
+
+			/* Config changed or leaving runlevel: stop, run post, restart */
+			svc->once = 0;
+			svc_stop(svc);
+			service_step(svc);
+			continue;
+		}
+
 		/* run/task declared with <!> */
 		if (svc->sighup)
 			svc->once = 1;

src/svc.h

@@ -139,6 +139,7 @@ typedef struct svc {
 	svc_type_t     type;	       /* Service, run, task, ... */
 	char           protect;        /* Services like dbus-daemon & udev by Finit */
 	char           manual;	       /* run/task that require `initctl start foo` */
+	char           remain;	       /* run/task: stay in DONE state, run post: on stop */
 	char           nowarn;	       /* Skip or log warning if cmd missing or conflicts */
 	const int      dirty;	       /* 0: unmodified, 1: modified */
 	const int      removed;
@@ -282,6 +283,7 @@ static inline int svc_is_tty       (svc_t *svc) { return svc && SVC_TYPE_TTY
 static inline int svc_is_runtask   (svc_t *svc) { return svc && (SVC_TYPE_RUNTASK & svc->type);}
 static inline int svc_is_forking   (svc_t *svc) { return svc && svc->forking; }
 static inline int svc_is_manual    (svc_t *svc) { return svc && svc->manual; }
+static inline int svc_is_remain    (svc_t *svc) { return svc && svc->remain; }
 static inline int svc_is_noreload  (svc_t *svc) { return svc && (0 == svc->sighup && 0 == svc->reload_script[0]); }
 
 static inline int svc_in_runlevel  (svc_t *svc, int runlevel) { return svc && ISSET(svc->runlevels, runlevel); }