confd: schedule: start crond only when a schedule is active

crond shipped auto-enabled in finit (symlinked into enabled/), so it ran
on every boot.  With no cron jobs /var/spool/cron/crontabs does not exist
and 'crond -f' exits non-zero, which finit then crash-loops until it gives
up ("Service crond keeps crashing, not restarting").

Ship crond available-only and let confd manage it: the schedule plugin
already rebuilds the crontab on every change, so enable + touch crond when
at least one consumer is active and disable it otherwise.  No jobs, no
crond, no crash loop.

Signed-off-by: Mattias Walström <lazzer@gmail.com>

package/confd/confd.mk

@@ -38,6 +38,8 @@ endif
 define CONFD_INSTALL_EXTRA
 	for fn in confd.conf crond.conf resolvconf.conf; do \
 		cp $(CONFD_PKGDIR)/$$fn  $(FINIT_D)/available/; \
+	done
+	for fn in confd.conf resolvconf.conf; do \
 		ln -sf ../available/$$fn $(FINIT_D)/enabled/$$fn; \
 	done
 	cp $(CONFD_PKGDIR)/tmpfiles.conf $(TARGET_DIR)/etc/tmpfiles.d/confd.conf

src/confd/src/schedule.c

@@ -176,11 +176,13 @@ done:
 	snprintf(expr, sz, "%s %s %s %s %s", min, hr, dom, mon, dow);
 }
 
-static void reload_crond(void)
+static void crond_apply(int active)
 {
-	char *args[] = { "pkill", "-HUP", "crond", NULL };
-
-	runbg(args, 0);
+	if (active) {
+		finit_enable("crond");
+	} else {
+		finit_disable("crond");
+	}
 }
 
 /*
@@ -267,7 +269,7 @@ static void apply_schedules(struct lyd_node *config)
 
 out:
 	fclose(fp);
-	reload_crond();
+	crond_apply(count > 0);
 	NOTE("schedule: %d active job(s) written to crontab", count);
 }