systemctl: make shutdown operations use irreversible jobs

Occasionally people report problem with reboot/poweroff operations hanging in
the middle. One known cause is when a new transaction to start a unit is
enqueued while the shutdown is going on. The start of the unit conflicts with
the shutdown jobs, so they get cancelled. The failure case can be quite unpleasant,
becase getty and sshd may already be stopped.

Fix it by using irreversible jobs for shutdown (reboot/poweroff/...) actions.
This applies to commands like "reboot", "telinit 6", "systemctl reboot". Should
someone desire to use reversible jobs, they can say "systemctl start reboot.target".`

2 files changed, 18 insertions, 7 deletions

diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index d235474a2..818f2fa80 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -1051,7 +1051,7 @@ static int execute_shutdown_or_sleep(
                 DBusError *error) {
 
         _cleanup_dbus_message_unref_ DBusMessage *reply = NULL;
-        const char *mode = "replace", *p;
+        const char *mode = "replace-irreversibly", *p;
         int r;
         char *c;
 
diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 723be76cd..3d59a8bb1 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -1595,11 +1595,22 @@ static int start_unit(DBusConnection *bus, char **args) {
                         streq(args[0], "force-reload")          ? "ReloadOrTryRestartUnit" :
                                                                   "StartUnit";
 
-                mode =
-                        (streq(args[0], "isolate") ||
-                         streq(args[0], "rescue")  ||
-                         streq(args[0], "emergency") ||
-                         streq(args[0], "default")) ? "isolate" : arg_job_mode;
+                if (streq(args[0], "isolate") ||
+                    streq(args[0], "rescue")  ||
+                    streq(args[0], "emergency") ||
+                    streq(args[0], "default"))
+                        mode = "isolate";
+                else if (streq(args[0], "halt") ||
+                         streq(args[0], "poweroff") ||
+                         streq(args[0], "reboot") ||
+                         streq(args[0], "kexec") ||
+                         streq(args[0], "exit") ||
+                         streq(args[0], "suspend") ||
+                         streq(args[0], "hibernate") ||
+                         streq(args[0], "hybrid-sleep"))
+                        mode = "replace-irreversibly";
+                else
+                        mode = arg_job_mode;
 
                 one_name = table[verb_to_action(args[0])];
 
@@ -1614,7 +1625,7 @@ static int start_unit(DBusConnection *bus, char **args) {
                         arg_action == ACTION_RUNLEVEL2 ||
                         arg_action == ACTION_RUNLEVEL3 ||
                         arg_action == ACTION_RUNLEVEL4 ||
-                        arg_action == ACTION_RUNLEVEL5) ? "isolate" : "replace";
+                        arg_action == ACTION_RUNLEVEL5) ? "isolate" : "replace-irreversibly";
 
                 one_name = table[arg_action];
         }