dbus: make errors reported via D-Bus more useful

19 files changed, 249 insertions, 145 deletions

diff --git a/Makefile.am b/Makefile.am
index b444c02f30..dfea23df4f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -311,7 +311,8 @@ EXTRA_DIST += \
 	src/initreq.h \
 	src/sd-daemon.h \
 	src/special.h \
-	src/dbus-common.h
+	src/dbus-common.h \
+	src/bus-errors.h
 
 MANPAGES = \
 	man/systemd.1 \
diff --git a/src/automount.c b/src/automount.c
index 0689ec7789..39eb3dd01a 100644
--- a/src/automount.c
+++ b/src/automount.c
@@ -35,6 +35,7 @@
 #include "load-dropin.h"
 #include "unit-name.h"
 #include "dbus-automount.h"
+#include "bus-errors.h"
 
 static const UnitActiveState state_translation_table[_AUTOMOUNT_STATE_MAX] = {
         [AUTOMOUNT_DEAD] = UNIT_INACTIVE,
@@ -533,10 +534,13 @@ fail:
 static void automount_enter_runnning(Automount *a) {
         int r;
         struct stat st;
+        DBusError error;
 
         assert(a);
         assert(a->mount);
 
+        dbus_error_init(&error);
+
         mkdir_p(a->where, a->directory_mode);
 
         /* Before we do anything, let's see if somebody is playing games with us? */
@@ -547,8 +551,8 @@ static void automount_enter_runnning(Automount *a) {
 
         if (!S_ISDIR(st.st_mode) || st.st_dev != a->dev_id)
                 log_info("%s's automount point already active?", a->meta.id);
-        else if ((r = manager_add_job(a->meta.manager, JOB_START, UNIT(a->mount), JOB_REPLACE, true, NULL)) < 0) {
-                log_warning("%s failed to queue mount startup job: %s", a->meta.id, strerror(-r));
+        else if ((r = manager_add_job(a->meta.manager, JOB_START, UNIT(a->mount), JOB_REPLACE, true, &error, NULL)) < 0) {
+                log_warning("%s failed to queue mount startup job: %s", a->meta.id, bus_error(&error, r));
                 goto fail;
         }
 
@@ -557,6 +561,7 @@ static void automount_enter_runnning(Automount *a) {
 
 fail:
         automount_enter_dead(a, false);
+        dbus_error_free(&error);
 }
 
 static int automount_start(Unit *u) {
diff --git a/src/dbus-manager.c b/src/dbus-manager.c
index dda7c771a5..5daccb14e8 100644
--- a/src/dbus-manager.c
+++ b/src/dbus-manager.c
@@ -25,6 +25,7 @@
 #include "log.h"
 #include "dbus-manager.h"
 #include "strv.h"
+#include "bus-errors.h"
 
 #define BUS_MANAGER_INTERFACE                                           \
         " <interface name=\"org.freedesktop.systemd1.Manager\">\n"      \
@@ -254,8 +255,10 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
                                     DBUS_TYPE_INVALID))
                         return bus_send_error_reply(m, connection, message, &error, -EINVAL);
 
-                if (!(u = manager_get_unit(m, name)))
-                        return bus_send_error_reply(m, connection, message, NULL, -ENOENT);
+                if (!(u = manager_get_unit(m, name))) {
+                        dbus_set_error(&error, BUS_ERROR_NO_SUCH_UNIT, "Unit %s is not loaded.", name);
+                        return bus_send_error_reply(m, connection, message, &error, -ENOENT);
+                }
 
                 if (!(reply = dbus_message_new_method_return(message)))
                         goto oom;
@@ -280,8 +283,8 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
                                     DBUS_TYPE_INVALID))
                         return bus_send_error_reply(m, connection, message, &error, -EINVAL);
 
-                if ((r = manager_load_unit(m, name, NULL, &u)) < 0)
-                        return bus_send_error_reply(m, connection, message, NULL, r);
+                if ((r = manager_load_unit(m, name, NULL, &error, &u)) < 0)
+                        return bus_send_error_reply(m, connection, message, &error, r);
 
                 if (!(reply = dbus_message_new_method_return(message)))
                         goto oom;
@@ -316,8 +319,10 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
                                     DBUS_TYPE_INVALID))
                         return bus_send_error_reply(m, connection, message, &error, -EINVAL);
 
-                if (!(j = manager_get_job(m, id)))
-                        return bus_send_error_reply(m, connection, message, NULL, -ENOENT);
+                if (!(j = manager_get_job(m, id))) {
+                        dbus_set_error(&error, BUS_ERROR_NO_SUCH_JOB, "Job %u does not exist.", (unsigned) id);
+                        return bus_send_error_reply(m, connection, message, &error, -ENOENT);
+                }
 
                 if (!(reply = dbus_message_new_method_return(message)))
                         goto oom;
@@ -496,8 +501,10 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
         } else if (dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "Unsubscribe")) {
                 char *client;
 
-                if (!(client = set_remove(BUS_CONNECTION_SUBSCRIBED(m, connection), (char*) message_get_sender_with_fallback(message))))
-                        return bus_send_error_reply(m, connection, message, NULL, -ENOENT);
+                if (!(client = set_remove(BUS_CONNECTION_SUBSCRIBED(m, connection), (char*) message_get_sender_with_fallback(message)))) {
+                        dbus_set_error(&error, BUS_ERROR_NOT_SUBSCRIBED, "Client is not subscribed.");
+                        return bus_send_error_reply(m, connection, message, &error, -ENOENT);
+                }
 
                 free(client);
 
@@ -548,8 +555,8 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
                 if (name && name[0] == 0)
                         name = NULL;
 
-                if ((r = snapshot_create(m, name, cleanup, &s)) < 0)
-                        return bus_send_error_reply(m, connection, message, NULL, r);
+                if ((r = snapshot_create(m, name, cleanup, &error, &s)) < 0)
+                        return bus_send_error_reply(m, connection, message, &error, r);
 
                 if (!(reply = dbus_message_new_method_return(message)))
                         goto oom;
@@ -648,8 +655,10 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
 
         } else if (dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "Exit")) {
 
-                if (m->running_as == MANAGER_SYSTEM)
-                        return bus_send_error_reply(m, connection, message, NULL, -ENOTSUP);
+                if (m->running_as == MANAGER_SYSTEM) {
+                        dbus_set_error(&error, BUS_ERROR_NOT_SUPPORTED, "Exit is only supported for session managers.");
+                        return bus_send_error_reply(m, connection, message, &error, -ENOTSUP);
+                }
 
                 if (!(reply = dbus_message_new_method_return(message)))
                         goto oom;
@@ -720,17 +729,21 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
                                     DBUS_TYPE_INVALID))
                         return bus_send_error_reply(m, connection, message, &error, -EINVAL);
 
-                if ((mode = job_mode_from_string(smode)) == _JOB_MODE_INVALID)
-                        return bus_send_error_reply(m, connection, message, NULL, -EINVAL);
+                if ((mode = job_mode_from_string(smode)) == _JOB_MODE_INVALID) {
+                        dbus_set_error(&error, BUS_ERROR_INVALID_JOB_MODE, "Job mode %s is invalid.", smode);
+                        return bus_send_error_reply(m, connection, message, &error, -EINVAL);
+                }
 
-                if ((r = manager_load_unit(m, name, NULL, &u)) < 0)
-                        return bus_send_error_reply(m, connection, message, NULL, r);
+                if ((r = manager_load_unit(m, name, NULL, &error, &u)) < 0)
+                        return bus_send_error_reply(m, connection, message, &error, r);
 
-                if (job_type == JOB_START && u->meta.only_by_dependency)
-                        return bus_send_error_reply(m, connection, message, NULL, -EPERM);
+                if (job_type == JOB_START && u->meta.only_by_dependency) {
+                        dbus_set_error(&error, BUS_ERROR_ONLY_BY_DEPENDENCY, "Unit may be activated by dependency only.");
+                        return bus_send_error_reply(m, connection, message, &error, -EPERM);
+                }
 
-                if ((r = manager_add_job(m, job_type, u, mode, true, &j)) < 0)
-                        return bus_send_error_reply(m, connection, message, NULL, r);
+                if ((r = manager_add_job(m, job_type, u, mode, true, &error, &j)) < 0)
+                        return bus_send_error_reply(m, connection, message, &error, r);
 
                 if (!(j->bus_client = strdup(message_get_sender_with_fallback(message))))
                         goto oom;
diff --git a/src/dbus-unit.c b/src/dbus-unit.c
index 85125c9633..840eaa571f 100644
--- a/src/dbus-unit.c
+++ b/src/dbus-unit.c
@@ -24,6 +24,7 @@
 #include "dbus.h"
 #include "log.h"
 #include "dbus-unit.h"
+#include "bus-errors.h"
 
 const char bus_unit_interface[] = BUS_UNIT_INTERFACE;
 
@@ -285,8 +286,10 @@ static DBusHandlerResult bus_unit_message_dispatch(Unit *u, DBusConnection *conn
                 Job *j;
                 int r;
 
-                if (job_type == JOB_START && u->meta.only_by_dependency)
-                        return bus_send_error_reply(m, connection, message, NULL, -EPERM);
+                if (job_type == JOB_START && u->meta.only_by_dependency) {
+                        dbus_set_error(&error, BUS_ERROR_ONLY_BY_DEPENDENCY, "Unit may be activated by dependency only.");
+                        return bus_send_error_reply(m, connection, message, &error, -EPERM);
+                }
 
                 if (!dbus_message_get_args(
                                     message,
@@ -295,11 +298,13 @@ static DBusHandlerResult bus_unit_message_dispatch(Unit *u, DBusConnection *conn
                                     DBUS_TYPE_INVALID))
                         return bus_send_error_reply(m, connection, message, &error, -EINVAL);
 
-                if ((mode = job_mode_from_string(smode)) == _JOB_MODE_INVALID)
-                        return bus_send_error_reply(m, connection, message, NULL, -EINVAL);
+                if ((mode = job_mode_from_string(smode)) == _JOB_MODE_INVALID) {
+                        dbus_set_error(&error, BUS_ERROR_INVALID_JOB_MODE, "Job mode %s is invalid.", smode);
+                        return bus_send_error_reply(m, connection, message, &error, -EINVAL);
+                }
 
-                if ((r = manager_add_job(m, job_type, u, mode, true, &j)) < 0)
-                        return bus_send_error_reply(m, connection, message, NULL, r);
+                if ((r = manager_add_job(m, job_type, u, mode, true, &error, &j)) < 0)
+                        return bus_send_error_reply(m, connection, message, &error, r);
 
                 if (!(reply = dbus_message_new_method_return(message)))
                         goto oom;
diff --git a/src/dbus.c b/src/dbus.c
index 0008cfd303..2998c58178 100644
--- a/src/dbus.c
+++ b/src/dbus.c
@@ -42,6 +42,7 @@
 #include "dbus-swap.h"
 #include "dbus-timer.h"
 #include "dbus-path.h"
+#include "bus-errors.h"
 
 #define CONNECTIONS_MAX 52
 
@@ -380,13 +381,13 @@ static DBusHandlerResult api_bus_message_filter(DBusConnection *connection, DBus
 
                         log_debug("Got D-Bus activation request for %s", name);
 
-                        r = manager_load_unit(m, name, NULL, &u);
+                        r = manager_load_unit(m, name, NULL, &error, &u);
 
                         if (r >= 0 && u->meta.only_by_dependency)
                                 r = -EPERM;
 
                         if (r >= 0)
-                                r = manager_add_job(m, JOB_START, u, JOB_REPLACE, true, NULL);
+                                r = manager_add_job(m, JOB_START, u, JOB_REPLACE, true, &error, NULL);
 
                         if (r < 0) {
                                 const char *id, *text;
@@ -396,8 +397,8 @@ static DBusHandlerResult api_bus_message_filter(DBusConnection *connection, DBus
                                 if (!(reply = dbus_message_new_signal("/org/freedesktop/systemd1", "org.freedesktop.systemd1.Activator", "ActivationFailure")))
                                         goto oom;
 
-                                id = error_to_dbus(r);
-                                text = strerror(-r);
+                                id = error.name ? error.name : error_to_dbus(r);
+                                text = bus_error(&error, r);
 
                                 if (!dbus_message_set_destination(reply, DBUS_SERVICE_DBUS) ||
                                     !dbus_message_append_args(reply,
@@ -1324,13 +1325,13 @@ static const char *error_to_dbus(int error) {
         return DBUS_ERROR_FAILED;
 }
 
-DBusHandlerResult bus_send_error_reply(Manager *m, DBusConnection *c, DBusMessage *message, DBusError *bus_error, int error) {
+DBusHandlerResult bus_send_error_reply(Manager *m, DBusConnection *c, DBusMessage *message, DBusError *berror, int error) {
         DBusMessage *reply = NULL;
         const char *name, *text;
 
-        if (bus_error && dbus_error_is_set(bus_error)) {
-                name = bus_error->name;
-                text = bus_error->message;
+        if (berror && dbus_error_is_set(berror)) {
+                name = berror->name;
+                text = berror->message;
         } else {
                 name = error_to_dbus(error);
                 text = strerror(-error);
@@ -1344,8 +1345,8 @@ DBusHandlerResult bus_send_error_reply(Manager *m, DBusConnection *c, DBusMessag
 
         dbus_message_unref(reply);
 
-        if (bus_error)
-                dbus_error_free(bus_error);
+        if (berror)
+                dbus_error_free(berror);
 
         return DBUS_HANDLER_RESULT_HANDLED;
 
@@ -1353,8 +1354,8 @@ oom:
         if (reply)
                 dbus_message_unref(reply);
 
-        if (bus_error)
-                dbus_error_free(bus_error);
+        if (berror)
+                dbus_error_free(berror);
 
         return DBUS_HANDLER_RESULT_NEED_MEMORY;
 }
diff --git a/src/load-fragment.c b/src/load-fragment.c
index c3909e9563..d474c9a88c 100644
--- a/src/load-fragment.c
+++ b/src/load-fragment.c
@@ -39,6 +39,7 @@
 #include "securebits.h"
 #include "missing.h"
 #include "unit-name.h"
+#include "bus-errors.h"
 
 #define COMMENTS "#;\n"
 
@@ -1057,14 +1058,23 @@ static int config_parse_timer_unit(
 
         Timer *t = data;
         int r;
+        DBusError error;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        dbus_error_init(&error);
 
         if (endswith(rvalue, ".timer")) {
                 log_error("[%s:%u] Unit cannot be of type timer: %s", filename, line, rvalue);
                 return -EINVAL;
         }
 
-        if ((r = manager_load_unit(t->meta.manager, rvalue, NULL, &t->unit)) < 0) {
-                log_error("[%s:%u] Failed to load unit: %s", filename, line, rvalue);
+        if ((r = manager_load_unit(t->meta.manager, rvalue, NULL, NULL, &t->unit)) < 0) {
+                log_error("[%s:%u] Failed to load unit %s: %s", filename, line, rvalue, bus_error(&error, r));
+                dbus_error_free(&error);
                 return r;
         }
 
@@ -1128,14 +1138,23 @@ static int config_parse_path_unit(
 
         Path *t = data;
         int r;
+        DBusError error;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        dbus_error_init(&error);
 
         if (endswith(rvalue, ".path")) {
                 log_error("[%s:%u] Unit cannot be of type path: %s", filename, line, rvalue);
                 return -EINVAL;
         }
 
-        if ((r = manager_load_unit(t->meta.manager, rvalue, NULL, &t->unit)) < 0) {
-                log_error("[%s:%u] Failed to load unit: %s", filename, line, rvalue);
+        if ((r = manager_load_unit(t->meta.manager, rvalue, NULL, &error, &t->unit)) < 0) {
+                log_error("[%s:%u] Failed to load unit %s: %s", filename, line, rvalue, bus_error(&error, r));
+                dbus_error_free(&error);
                 return r;
         }
 
diff --git a/src/main.c b/src/main.c
index d5902b354f..3124b7644e 100644
--- a/src/main.c
+++ b/src/main.c
@@ -43,6 +43,7 @@
 #include "fdset.h"
 #include "special.h"
 #include "conf-parser.h"
+#include "bus-errors.h"
 
 static enum {
         ACTION_RUN,
@@ -963,14 +964,20 @@ int main(int argc, char *argv[]) {
                 fclose(serialization);
                 serialization = NULL;
         } else {
+                DBusError error;
+
+                dbus_error_init(&error);
+
                 log_debug("Activating default unit: %s", arg_default_unit);
 
-                if ((r = manager_load_unit(m, arg_default_unit, NULL, &target)) < 0) {
-                        log_error("Failed to load default target: %s", strerror(-r));
+                if ((r = manager_load_unit(m, arg_default_unit, NULL, &error, &target)) < 0) {
+                        log_error("Failed to load default target: %s", bus_error(&error, r));
+                        dbus_error_free(&error);
 
                         log_info("Trying to load rescue target...");
-                        if ((r = manager_load_unit(m, SPECIAL_RESCUE_TARGET, NULL, &target)) < 0) {
-                                log_error("Failed to load rescue target: %s", strerror(-r));
+                        if ((r = manager_load_unit(m, SPECIAL_RESCUE_TARGET, NULL, &error, &target)) < 0) {
+                                log_error("Failed to load rescue target: %s", bus_error(&error, r));
+                                dbus_error_free(&error);
                                 goto finish;
                         }
                 }
@@ -980,8 +987,9 @@ int main(int argc, char *argv[]) {
                         manager_dump_units(m, stdout, "\t");
                 }
 
-                if ((r = manager_add_job(m, JOB_START, target, JOB_REPLACE, false, &job)) < 0) {
-                        log_error("Failed to start default target: %s", strerror(-r));
+                if ((r = manager_add_job(m, JOB_START, target, JOB_REPLACE, false, &error, &job)) < 0) {
+                        log_error("Failed to start default target: %s", bus_error(&error, r));
+                        dbus_error_free(&error);
                         goto finish;
                 }
 
diff --git a/src/manager.c b/src/manager.c
index c1f70e815c..9cbf9c8748 100644
--- a/src/manager.c
+++ b/src/manager.c
@@ -53,6 +53,7 @@
 #include "missing.h"
 #include "path-lookup.h"
 #include "special.h"
+#include "bus-errors.h"
 
 /* As soon as 16 units are in our GC queue, make sure to run a gc sweep */
 #define GC_QUEUE_ENTRIES_MAX 16
@@ -697,7 +698,7 @@ static int delete_one_unmergeable_job(Manager *m, Job *j) {
         return -EINVAL;
 }
 
-static int transaction_merge_jobs(Manager *m) {
+static int transaction_merge_jobs(Manager *m, DBusError *e) {
         Job *j;
         Iterator i;
         int r;
@@ -726,6 +727,8 @@ static int transaction_merge_jobs(Manager *m) {
                                 return -EAGAIN;
 
                         /* We couldn't merge anything. Failure */
+                        dbus_set_error(e, BUS_ERROR_TRANSACTION_JOBS_CONFLICTING, "Transaction contains conflicting jobs '%s' and '%s' for %s. Probably contradicting requirement dependencies configured.",
+                                       job_type_to_string(t), job_type_to_string(k->type), k->unit->meta.id);
                         return r;
                 }
         }
@@ -812,7 +815,7 @@ static bool unit_matters_to_anchor(Unit *u, Job *j) {
         return false;
 }
 
-static int transaction_verify_order_one(Manager *m, Job *j, Job *from, unsigned generation) {
+static int transaction_verify_order_one(Manager *m, Job *j, Job *from, unsigned generation, DBusError *e) {
         Iterator i;
         Unit *u;
         int r;
@@ -863,6 +866,7 @@ static int transaction_verify_order_one(Manager *m, Job *j, Job *from, unsigned
 
                 log_error("Unable to break cycle");
 
+                dbus_set_error(e, BUS_ERROR_TRANSACTION_ORDER_IS_CYCLIC, "Transaction order is cyclic. See logs for details.");
                 return -ENOEXEC;
         }
 
@@ -887,7 +891,7 @@ static int transaction_verify_order_one(Manager *m, Job *j, Job *from, unsigned
                         if (!(o = u->meta.job))
                                 continue;
 
-                if ((r = transaction_verify_order_one(m, o, j, generation)) < 0)
+                if ((r = transaction_verify_order_one(m, o, j, generation, e)) < 0)
                         return r;
         }
 
@@ -898,7 +902,7 @@ static int transaction_verify_order_one(Manager *m, Job *j, Job *from, unsigned
         return 0;
 }
 
-static int transaction_verify_order(Manager *m, unsigned *generation) {
+static int transaction_verify_order(Manager *m, unsigned *generation, DBusError *e) {
         Job *j;
         int r;
         Iterator i;
@@ -913,7 +917,7 @@ static int transaction_verify_order(Manager *m, unsigned *generation) {
         g = (*generation)++;
 
         HASHMAP_FOREACH(j, m->transaction_jobs, i)
-                if ((r = transaction_verify_order_one(m, j, NULL, g)) < 0)
+                if ((r = transaction_verify_order_one(m, j, NULL, g, e)) < 0)
                         return r;
 
         return 0;
@@ -945,7 +949,7 @@ static void transaction_collect_garbage(Manager *m) {
         } while (again);
 }
 
-static int transaction_is_destructive(Manager *m) {
+static int transaction_is_destructive(Manager *m, DBusError *e) {
         Iterator i;
         Job *j;
 
@@ -962,8 +966,11 @@ static int transaction_is_destructive(Manager *m) {
 
                 if (j->unit->meta.job &&
                     j->unit->meta.job != j &&
-                    !job_type_is_superset(j->type, j->unit->meta.job->type))
+                    !job_type_is_superset(j->type, j->unit->meta.job->type)) {
+
+                        dbus_set_error(e, BUS_ERROR_TRANSACTION_IS_DESTRUCTIVE, "Transaction is destructive.");
                         return -EEXIST;
+                }
         }
 
         return 0;
@@ -1080,7 +1087,7 @@ rollback:
         return r;
 }
 
-static int transaction_activate(Manager *m, JobMode mode) {
+static int transaction_activate(Manager *m, JobMode mode, DBusError *e) {
         int r;
         unsigned generation = 1;
 
@@ -1107,11 +1114,11 @@ static int transaction_activate(Manager *m, JobMode mode) {
 
                 /* Fifth step: verify order makes sense and correct
                  * cycles if necessary and possible */
-                if ((r = transaction_verify_order(m, &generation)) >= 0)
+                if ((r = transaction_verify_order(m, &generation, e)) >= 0)
                         break;
 
                 if (r != -EAGAIN) {
-                        log_warning("Requested transaction contains an unfixable cyclic ordering dependency: %s", strerror(-r));
+                        log_warning("Requested transaction contains an unfixable cyclic ordering dependency: %s", bus_error(e, r));
                         goto rollback;
                 }
 
@@ -1123,11 +1130,11 @@ static int transaction_activate(Manager *m, JobMode mode) {
                 /* Sixth step: let's drop unmergeable entries if
                  * necessary and possible, merge entries we can
                  * merge */
-                if ((r = transaction_merge_jobs(m)) >= 0)
+                if ((r = transaction_merge_jobs(m, e)) >= 0)
                         break;
 
                 if (r != -EAGAIN) {
-                        log_warning("Requested transaction contains unmergable jobs: %s", strerror(-r));
+                        log_warning("Requested transaction contains unmergable jobs: %s", bus_error(e, r));
                         goto rollback;
                 }
 
@@ -1144,8 +1151,8 @@ static int transaction_activate(Manager *m, JobMode mode) {
 
         /* Ninth step: check whether we can actually apply this */
         if (mode == JOB_FAIL)
-                if ((r = transaction_is_destructive(m)) < 0) {
-                        log_notice("Requested transaction contradicts existing jobs: %s", strerror(-r));
+                if ((r = transaction_is_destructive(m, e)) < 0) {
+                        log_notice("Requested transaction contradicts existing jobs: %s", bus_error(e, r));
                         goto rollback;
                 }
 
@@ -1253,6 +1260,7 @@ static int transaction_add_job_and_dependencies(
                 Job *by,
                 bool matters,
                 bool override,
+                DBusError *e,
                 Job **_ret) {
         Job *ret;
         Iterator i;
@@ -1264,11 +1272,15 @@ static int transaction_add_job_and_dependencies(
         assert(type < _JOB_TYPE_MAX);
         assert(unit);
 
-        if (unit->meta.load_state != UNIT_LOADED)
+        if (unit->meta.load_state != UNIT_LOADED) {
+                dbus_set_error(e, BUS_ERROR_LOAD_FAILED, "Unit %s failed to load.", unit->meta.id);
                 return -EINVAL;
+        }
 
-        if (!unit_job_is_applicable(unit, type))
+        if (!unit_job_is_applicable(unit, type)) {
+                dbus_set_error(e, BUS_ERROR_JOB_TYPE_NOT_APPLICABLE, "Job type %s is not applicable for unit %s.", job_type_to_string(type), unit->meta.id);
                 return -EBADR;
+        }
 
         /* First add the job. */
         if (!(ret = transaction_add_one_job(m, type, unit, override, &is_new)))
@@ -1282,33 +1294,33 @@ static int transaction_add_job_and_dependencies(
                 /* Finally, recursively add in all dependencies. */
                 if (type == JOB_START || type == JOB_RELOAD_OR_START) {
                         SET_FOREACH(dep, ret->unit->meta.dependencies[UNIT_REQUIRES], i)
-                                if ((r = transaction_add_job_and_dependencies(m, JOB_START, dep, ret, true, override, NULL)) < 0 && r != -EBADR)
+                                if ((r = transaction_add_job_and_dependencies(m, JOB_START, dep, ret, true, override, e, NULL)) < 0 && r != -EBADR)
                                         goto fail;
 
                         SET_FOREACH(dep, ret->unit->meta.dependencies[UNIT_REQUIRES_OVERRIDABLE], i)
-                                if ((r = transaction_add_job_and_dependencies(m, JOB_START, dep, ret, !override, override, NULL)) < 0 && r != -EBADR)
+                                if ((r = transaction_add_job_and_dependencies(m, JOB_START, dep, ret, !override, override, e, NULL)) < 0 && r != -EBADR)
                                         log_warning("Cannot add dependency job for unit %s, ignoring: %s", dep->meta.id, strerror(-r));
 
                         SET_FOREACH(dep, ret->unit->meta.dependencies[UNIT_WANTS], i)
-                                if ((r = transaction_add_job_and_dependencies(m, JOB_START, dep, ret, false, false, NULL)) < 0)
+                                if ((r = transaction_add_job_and_dependencies(m, JOB_START, dep, ret, false, false, e, NULL)) < 0)
                                         log_warning("Cannot add dependency job for unit %s, ignoring: %s", dep->meta.id, strerror(-r));
 
                         SET_FOREACH(dep, ret->unit->meta.dependencies[UNIT_REQUISITE], i)
-                                if ((r = transaction_add_job_and_dependencies(m, JOB_VERIFY_ACTIVE, dep, ret, true, override, NULL)) < 0 && r != -EBADR)
+                                if ((r = transaction_add_job_and_dependencies(m, JOB_VERIFY_ACTIVE, dep, ret, true, override, e, NULL)) < 0 && r != -EBADR)
                                         goto fail;
 
                         SET_FOREACH(dep, ret->unit->meta.dependencies[UNIT_REQUISITE_OVERRIDABLE], i)
-                                if ((r = transaction_add_job_and_dependencies(m, JOB_VERIFY_ACTIVE, dep, ret, !override, override, NULL)) < 0 && r != -EBADR)
+                                if ((r = transaction_add_job_and_dependencies(m, JOB_VERIFY_ACTIVE, dep, ret, !override, override, e, NULL)) < 0 && r != -EBADR)
                                         log_warning("Cannot add dependency job for unit %s, ignoring: %s", dep->meta.id, strerror(-r));
 
                         SET_FOREACH(dep, ret->unit->meta.dependencies[UNIT_CONFLICTS], i)
-                                if ((r = transaction_add_job_and_dependencies(m, JOB_STOP, dep, ret, true, override, NULL)) < 0 && r != -EBADR)
+                                if ((r = transaction_add_job_and_dependencies(m, JOB_STOP, dep, ret, true, override, e, NULL)) < 0 && r != -EBADR)
                                         goto fail;
 
                 } else if (type == JOB_STOP || type == JOB_RESTART || type == JOB_TRY_RESTART) {
 
                         SET_FOREACH(dep, ret->unit->meta.dependencies[UNIT_REQUIRED_BY], i)
-                                if ((r = transaction_add_job_and_dependencies(m, type, dep, ret, true, override, NULL)) < 0 && r != -EBADR)
+                                if ((r = transaction_add_job_and_dependencies(m, type, dep, ret, true, override, e, NULL)) < 0 && r != -EBADR)
                                         goto fail;
                 }
 
@@ -1349,14 +1361,14 @@ static int transaction_add_isolate_jobs(Manager *m) {
                 if (hashmap_get(m->transaction_jobs, u))
                         continue;
 
-                if ((r = transaction_add_job_and_dependencies(m, JOB_STOP, u, NULL, true, false, NULL)) < 0)
+                if ((r = transaction_add_job_and_dependencies(m, JOB_STOP, u, NULL, true, false, NULL, NULL)) < 0)
                         log_warning("Cannot add isolate job for unit %s, ignoring: %s", u->meta.id, strerror(-r));
         }
 
         return 0;
 }
 
-int manager_add_job(Manager *m, JobType type, Unit *unit, JobMode mode, bool override, Job **_ret) {
+int manager_add_job(Manager *m, JobType type, Unit *unit, JobMode mode, bool override, DBusError *e, Job **_ret) {
         int r;
         Job *ret;
 
@@ -1365,12 +1377,14 @@ int manager_add_job(Manager *m, JobType type, Unit *unit, JobMode mode, bool ove
         assert(unit);
         assert(mode < _JOB_MODE_MAX);
 
-        if (mode == JOB_ISOLATE && type != JOB_START)
+        if (mode == JOB_ISOLATE && type != JOB_START) {
+                dbus_set_error(e, BUS_ERROR_INVALID_JOB_MODE, "Isolate is only valid for start.");
                 return -EINVAL;
+        }
 
         log_debug("Trying to enqueue job %s/%s", unit->meta.id, job_type_to_string(type));
 
-        if ((r = transaction_add_job_and_dependencies(m, type, unit, NULL, true, override, &ret)) < 0) {
+        if ((r = transaction_add_job_and_dependencies(m, type, unit, NULL, true, override, e, &ret)) < 0) {
                 transaction_abort(m);
                 return r;
         }
@@ -1381,7 +1395,7 @@ int manager_add_job(Manager *m, JobType type, Unit *unit, JobMode mode, bool ove
                         return r;
                 }
 
-        if ((r = transaction_activate(m, mode)) < 0)
+        if ((r = transaction_activate(m, mode, e)) < 0)
                 return r;
 
         log_debug("Enqueued job %s/%s as %u", unit->meta.id, job_type_to_string(type), (unsigned) ret->id);
@@ -1392,7 +1406,7 @@ int manager_add_job(Manager *m, JobType type, Unit *unit, JobMode mode, bool ove
         return 0;
 }
 
-int manager_add_job_by_name(Manager *m, JobType type, const char *name, JobMode mode, bool override, Job **_ret) {
+int manager_add_job_by_name(Manager *m, JobType type, const char *name, JobMode mode, bool override, DBusError *e, Job **_ret) {
         Unit *unit;
         int r;
 
@@ -1401,10 +1415,10 @@ int manager_add_job_by_name(Manager *m, JobType type, const char *name, JobMode
         assert(name);
         assert(mode < _JOB_MODE_MAX);
 
-        if ((r = manager_load_unit(m, name, NULL, &unit)) < 0)
+        if ((r = manager_load_unit(m, name, NULL, NULL, &unit)) < 0)
                 return r;
 
-        return manager_add_job(m, type, unit, mode, override, _ret);
+        return manager_add_job(m, type, unit, mode, override, e, _ret);
 }
 
 Job *manager_get_job(Manager *m, uint32_t id) {
@@ -1446,7 +1460,7 @@ unsigned manager_dispatch_load_queue(Manager *m) {
         return n;
 }
 
-int manager_load_unit_prepare(Manager *m, const char *name, const char *path, Unit **_ret) {
+int manager_load_unit_prepare(Manager *m, const char *name, const char *path, DBusError *e, Unit **_ret) {
         Unit *ret;
         int r;
 
@@ -1456,14 +1470,18 @@ int manager_load_unit_prepare(Manager *m, const char *name, const char *path, Un
         /* This will prepare the unit for loading, but not actually
          * load anything from disk. */
 
-        if (path && !is_path(path))
+        if (path && !is_path(path)) {
+                dbus_set_error(e, BUS_ERROR_INVALID_PATH, "Path %s is not absolute.", path);
                 return -EINVAL;
+        }
 
         if (!name)
                 name = file_name_from_path(path);
 
-        if (!unit_name_is_valid(name))
+        if (!unit_name_is_valid(name)) {
+                dbus_set_error(e, BUS_ERROR_INVALID_NAME, "Unit name %s is not valid.", name);
                 return -EINVAL;
+        }
 
         if ((ret = manager_get_unit(m, name))) {
                 *_ret = ret;
@@ -1494,7 +1512,7 @@ int manager_load_unit_prepare(Manager *m, const char *name, const char *path, Un
         return 0;
 }
 
-int manager_load_unit(Manager *m, const char *name, const char *path, Unit **_ret) {
+int manager_load_unit(Manager *m, const char *name, const char *path, DBusError *e, Unit **_ret) {
         int r;
 
         assert(m);
@@ -1502,7 +1520,7 @@ int manager_load_unit(Manager *m, const char *name, const char *path, Unit **_re
         /* This will load the service information files, but not actually
          * start any services or anything. */
 
-        if ((r = manager_load_unit_prepare(m, name, path, _ret)) != 0)
+        if ((r = manager_load_unit_prepare(m, name, path, e, _ret)) != 0)
                 return r;
 
         manager_dispatch_load_queue(m);
@@ -1746,9 +1764,14 @@ static int manager_dispatch_sigchld(Manager *m) {
 
 static int manager_start_target(Manager *m, const char *name, JobMode mode) {
         int r;
+        DBusError error;
+
+        dbus_error_init(&error);
+
+        if ((r = manager_add_job_by_name(m, JOB_START, name, mode, true, &error, NULL)) < 0)
+                log_error("Failed to enqueue %s job: %s", name, bus_error(&error, r));
 
-        if ((r = manager_add_job_by_name(m, JOB_START, name, mode, true, NULL)) < 0)
-                log_error("Failed to enqueue %s job: %s", name, strerror(-r));
+        dbus_error_free(&error);
 
         return r;
 }
@@ -2266,7 +2289,7 @@ int manager_deserialize(Manager *m, FILE *f, FDSet *fds) {
 
                 char_array_0(name);
 
-                if ((r = manager_load_unit(m, strstrip(name), NULL, &u)) < 0)
+                if ((r = manager_load_unit(m, strstrip(name), NULL, NULL, &u)) < 0)
                         return r;
 
                 if ((r = unit_deserialize(u, f, fds)) < 0)
diff --git a/src/manager.h b/src/manager.h
index 5b3aaf3364..e5cf3a1c52 100644
--- a/src/manager.h
+++ b/src/manager.h
@@ -210,11 +210,11 @@ Unit *manager_get_unit(Manager *m, const char *name);
 int manager_get_unit_from_dbus_path(Manager *m, const char *s, Unit **_u);
 int manager_get_job_from_dbus_path(Manager *m, const char *s, Job **_j);
 
-int manager_load_unit_prepare(Manager *m, const char *name, const char *path, Unit **_ret);
-int manager_load_unit(Manager *m, const char *name, const char *path, Unit **_ret);
+int manager_load_unit_prepare(Manager *m, const char *name, const char *path, DBusError *e, Unit **_ret);
+int manager_load_unit(Manager *m, const char *name, const char *path, DBusError *e, Unit **_ret);
 
-int manager_add_job(Manager *m, JobType type, Unit *unit, JobMode mode, bool force, Job **_ret);
-int manager_add_job_by_name(Manager *m, JobType type, const char *name, JobMode mode, bool force, Job **_ret);
+int manager_add_job(Manager *m, JobType type, Unit *unit, JobMode mode, bool force, DBusError *e, Job **_ret);
+int manager_add_job_by_name(Manager *m, JobType type, const char *name, JobMode mode, bool force, DBusError *e, Job **_ret);
 
 void manager_dump_units(Manager *s, FILE *f, const char *prefix);
 void manager_dump_jobs(Manager *s, FILE *f, const char *prefix);
diff --git a/src/mount.c b/src/mount.c
index 49081d1d97..50fe85cb7c 100644
--- a/src/mount.c
+++ b/src/mount.c
@@ -253,7 +253,7 @@ static int mount_add_target_links(Mount *m) {
         else
                 target = SPECIAL_LOCAL_FS_TARGET;
 
-        if ((r = manager_load_unit(m->meta.manager, target, NULL, &tu)) < 0)
+        if ((r = manager_load_unit(m->meta.manager, target, NULL, NULL, &tu)) < 0)
                 return r;
 
         if (automount && m->meta.manager->running_as == MANAGER_SYSTEM) {
diff --git a/src/path.c b/src/path.c
index 30d946d788..27c4544729 100644
--- a/src/path.c
+++ b/src/path.c
@@ -30,6 +30,7 @@
 #include "path.h"
 #include "dbus-path.h"
 #include "special.h"
+#include "bus-errors.h"
 
 static const UnitActiveState state_translation_table[_PATH_STATE_MAX] = {
         [PATH_DEAD] = UNIT_INACTIVE,
@@ -298,17 +299,22 @@ static void path_enter_dead(Path *p, bool success) {
 
 static void path_enter_running(Path *p) {
         int r;
+        DBusError error;
+
         assert(p);
+        dbus_error_init(&error);
 
-        if ((r = manager_add_job(p->meta.manager, JOB_START, p->unit, JOB_REPLACE, true, NULL)) < 0)
+        if ((r = manager_add_job(p->meta.manager, JOB_START, p->unit, JOB_REPLACE, true, &error, NULL)) < 0)
                 goto fail;
 
         path_set_state(p, PATH_RUNNING);
         return;
 
 fail:
-        log_warning("%s failed to queue unit startup job: %s", p->meta.id, strerror(-r));
+        log_warning("%s failed to queue unit startup job: %s", p->meta.id, bus_error(&error, r));
         path_enter_dead(p, false);
+
+        dbus_error_free(&error);
 }
 
 
diff --git a/src/service.c b/src/service.c
index 35f2e9ad2c..75439be376 100644
--- a/src/service.c
+++ b/src/service.c
@@ -33,6 +33,7 @@
 #include "unit-name.h"
 #include "dbus-service.h"
 #include "special.h"
+#include "bus-errors.h"
 
 #define COMMENTS "#;\n"
 #define NEWLINES "\n\r"
@@ -1763,20 +1764,24 @@ fail:
 
 static void service_enter_restart(Service *s) {
         int r;
+        DBusError error;
+
         assert(s);
+        dbus_error_init(&error);
 
         service_enter_dead(s, true, false);
 
-        if ((r = manager_add_job(s->meta.manager, JOB_START, UNIT(s), JOB_FAIL, false, NULL)) < 0)
+        if ((r = manager_add_job(s->meta.manager, JOB_START, UNIT(s), JOB_FAIL, false, NULL, NULL)) < 0)
                 goto fail;
 
         log_debug("%s scheduled restart job.", s->meta.id);
         return;
 
 fail:
-
-        log_warning("%s failed to schedule restart job: %s", s->meta.id, strerror(-r));
+        log_warning("%s failed to schedule restart job: %s", s->meta.id, bus_error(&error, -r));
         service_enter_dead(s, false, false);
+
+        dbus_error_free(&error);
 }
 
 static void service_enter_reload(Service *s) {
@@ -2538,7 +2543,7 @@ static int service_enumerate(Manager *m) {
                                         goto finish;
                                 }
 
-                                if ((r = manager_load_unit_prepare(m, name, NULL, &service)) < 0) {
+                                if ((r = manager_load_unit_prepare(m, name, NULL, NULL, &service)) < 0) {
                                         log_warning("Failed to prepare unit %s: %s", name, strerror(-r));
                                         continue;
                                 }
diff --git a/src/snapshot.c b/src/snapshot.c
index ba72edc255..fe8a43dd3a 100644
--- a/src/snapshot.c
+++ b/src/snapshot.c
@@ -25,6 +25,7 @@
 #include "snapshot.h"
 #include "unit-name.h"
 #include "dbus-snapshot.h"
+#include "bus-errors.h"
 
 static const UnitActiveState state_translation_table[_SNAPSHOT_STATE_MAX] = {
         [SNAPSHOT_DEAD] = UNIT_INACTIVE,
@@ -174,7 +175,7 @@ static const char *snapshot_sub_state_to_string(Unit *u) {
         return snapshot_state_to_string(SNAPSHOT(u)->state);
 }
 
-int snapshot_create(Manager *m, const char *name, bool cleanup, Snapshot **_s) {
+int snapshot_create(Manager *m, const char *name, bool cleanup, DBusError *e, Snapshot **_s) {
         Iterator i;
         Unit *other, *u = NULL;
         char *n = NULL;
@@ -185,14 +186,20 @@ int snapshot_create(Manager *m, const char *name, bool cleanup, Snapshot **_s) {
         assert(_s);
 
         if (name) {
-                if (!unit_name_is_valid(name))
+                if (!unit_name_is_valid(name)) {
+                        dbus_set_error(e, BUS_ERROR_INVALID_NAME, "Unit name %s is not valid.", name);
                         return -EINVAL;
+                }
 
-                if (unit_name_to_type(name) != UNIT_SNAPSHOT)
+                if (unit_name_to_type(name) != UNIT_SNAPSHOT) {
+                        dbus_set_error(e, BUS_ERROR_UNIT_TYPE_MISMATCH, "Unit name %s lacks snapshot suffix.", name);
                         return -EINVAL;
+                }
 
-                if (manager_get_unit(m, name))
+                if (manager_get_unit(m, name)) {
+                        dbus_set_error(e, BUS_ERROR_UNIT_EXISTS, "Snapshot %s exists already.", name);
                         return -EEXIST;
+                }
 
         } else {
 
@@ -209,7 +216,7 @@ int snapshot_create(Manager *m, const char *name, bool cleanup, Snapshot **_s) {
                 name = n;
         }
 
-        r = manager_load_unit_prepare(m, name, NULL, &u);
+        r = manager_load_unit_prepare(m, name, NULL, e, &u);
         free(n);
 
         if (r < 0)
diff --git a/src/snapshot.h b/src/snapshot.h
index 2561790639..2b5f3c338a 100644
--- a/src/snapshot.h
+++ b/src/snapshot.h
@@ -44,7 +44,7 @@ struct Snapshot {
 
 extern const UnitVTable snapshot_vtable;
 
-int snapshot_create(Manager *m, const char *name, bool cleanup, Snapshot **s);
+int snapshot_create(Manager *m, const char *name, bool cleanup, DBusError *e, Snapshot **s);
 void snapshot_remove(Snapshot *s);
 
 const char* snapshot_state_to_string(SnapshotState i);
diff --git a/src/socket.c b/src/socket.c
index 00e0685aad..b8643d9f43 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -38,6 +38,7 @@
 #include "dbus-socket.h"
 #include "missing.h"
 #include "special.h"
+#include "bus-errors.h"
 
 static const UnitActiveState state_translation_table[_SOCKET_STATE_MAX] = {
         [SOCKET_DEAD] = UNIT_INACTIVE,
@@ -1025,11 +1026,13 @@ fail:
 
 static void socket_enter_running(Socket *s, int cfd) {
         int r;
+        DBusError error;
 
         assert(s);
+        dbus_error_init(&error);
 
         if (cfd < 0) {
-                if ((r = manager_add_job(s->meta.manager, JOB_START, UNIT(s->service), JOB_REPLACE, true, NULL)) < 0)
+                if ((r = manager_add_job(s->meta.manager, JOB_START, UNIT(s->service), JOB_REPLACE, true, &error, NULL)) < 0)
                         goto fail;
 
                 socket_set_state(s, SOCKET_RUNNING);
@@ -1061,7 +1064,7 @@ static void socket_enter_running(Socket *s, int cfd) {
                         goto fail;
                 }
 
-                r = manager_load_unit(s->meta.manager, name, NULL, &u);
+                r = manager_load_unit(s->meta.manager, name, NULL, NULL, &u);
                 free(name);
 
                 if (r < 0)
@@ -1074,18 +1077,20 @@ static void socket_enter_running(Socket *s, int cfd) {
 
                 s->n_connections ++;
 
-                if ((r = manager_add_job(u->meta.manager, JOB_START, u, JOB_REPLACE, true, NULL)) < 0)
+                if ((r = manager_add_job(u->meta.manager, JOB_START, u, JOB_REPLACE, true, &error, NULL)) < 0)
                         goto fail;
         }
 
         return;
 
 fail:
-        log_warning("%s failed to queue socket startup job: %s", s->meta.id, strerror(-r));
+        log_warning("%s failed to queue socket startup job: %s", s->meta.id, bus_error(&error, r));
         socket_enter_stop_pre(s, false);
 
         if (cfd >= 0)
                 close_nointr_nofail(cfd);
+
+        dbus_error_free(&error);
 }
 
 static void socket_run_next(Socket *s, bool success) {
diff --git a/src/swap.c b/src/swap.c
index f72ede66d0..92035144ba 100644
--- a/src/swap.c
+++ b/src/swap.c
@@ -110,7 +110,7 @@ static int swap_add_target_links(Swap *s) {
         else
                 return 0;
 
-        if ((r = manager_load_unit(s->meta.manager, SPECIAL_SWAP_TARGET, NULL, &tu)) < 0)
+        if ((r = manager_load_unit(s->meta.manager, SPECIAL_SWAP_TARGET, NULL, NULL, &tu)) < 0)
                 return r;
 
         if (!p->noauto && p->handle && s->meta.manager->running_as == MANAGER_SYSTEM)
diff --git a/src/test-engine.c b/src/test-engine.c
index 89631c4659..d10196b12f 100644
--- a/src/test-engine.c
+++ b/src/test-engine.c
@@ -36,61 +36,61 @@ int main(int argc, char *argv[]) {
         assert_se(manager_new(MANAGER_SYSTEM, &m) >= 0);
 
         printf("Load1:\n");
-        assert_se(manager_load_unit(m, "a.service", NULL, &a) >= 0);
-        assert_se(manager_load_unit(m, "b.service", NULL, &b) >= 0);
-        assert_se(manager_load_unit(m, "c.service", NULL, &c) >= 0);
+        assert_se(manager_load_unit(m, "a.service", NULL, NULL, &a) >= 0);
+        assert_se(manager_load_unit(m, "b.service", NULL, NULL, &b) >= 0);
+        assert_se(manager_load_unit(m, "c.service", NULL, NULL, &c) >= 0);
         manager_dump_units(m, stdout, "\t");
 
         printf("Test1: (Trivial)\n");
-        assert_se(manager_add_job(m, JOB_START, c, JOB_REPLACE, false, &j) == 0);
+        assert_se(manager_add_job(m, JOB_START, c, JOB_REPLACE, false, NULL, &j) == 0);
         manager_dump_jobs(m, stdout, "\t");
 
         printf("Load2:\n");
         manager_clear_jobs(m);
-        assert_se(manager_load_unit(m, "d.service", NULL, &d) >= 0);
-        assert_se(manager_load_unit(m, "e.service", NULL, &e) >= 0);
+        assert_se(manager_load_unit(m, "d.service", NULL, NULL, &d) >= 0);
+        assert_se(manager_load_unit(m, "e.service", NULL, NULL, &e) >= 0);
         manager_dump_units(m, stdout, "\t");
 
         printf("Test2: (Cyclic Order, Unfixable)\n");
-        assert_se(manager_add_job(m, JOB_START, d, JOB_REPLACE, false, &j) == -ENOEXEC);
+        assert_se(manager_add_job(m, JOB_START, d, JOB_REPLACE, false, NULL, &j) == -ENOEXEC);
         manager_dump_jobs(m, stdout, "\t");
 
         printf("Test3: (Cyclic Order, Fixable, Garbage Collector)\n");
-        assert_se(manager_add_job(m, JOB_START, e, JOB_REPLACE, false, &j) == 0);
+        assert_se(manager_add_job(m, JOB_START, e, JOB_REPLACE, false, NULL, &j) == 0);
         manager_dump_jobs(m, stdout, "\t");
 
         printf("Test4: (Identical transaction)\n");
-        assert_se(manager_add_job(m, JOB_START, e, JOB_FAIL, false, &j) == 0);
+        assert_se(manager_add_job(m, JOB_START, e, JOB_FAIL, false, NULL, &j) == 0);
         manager_dump_jobs(m, stdout, "\t");
 
         printf("Load3:\n");
-        assert_se(manager_load_unit(m, "g.service", NULL, &g) >= 0);
+        assert_se(manager_load_unit(m, "g.service", NULL, NULL, &g) >= 0);
         manager_dump_units(m, stdout, "\t");
 
         printf("Test5: (Colliding transaction, fail)\n");
-        assert_se(manager_add_job(m, JOB_START, g, JOB_FAIL, false, &j) == -EEXIST);
+        assert_se(manager_add_job(m, JOB_START, g, JOB_FAIL, false, NULL, &j) == -EEXIST);
 
         printf("Test6: (Colliding transaction, replace)\n");
-        assert_se(manager_add_job(m, JOB_START, g, JOB_REPLACE, false, &j) == 0);
+        assert_se(manager_add_job(m, JOB_START, g, JOB_REPLACE, false, NULL, &j) == 0);
         manager_dump_jobs(m, stdout, "\t");
 
         printf("Test7: (Unmeargable job type, fail)\n");
-        assert_se(manager_add_job(m, JOB_STOP, g, JOB_FAIL, false, &j) == -EEXIST);
+        assert_se(manager_add_job(m, JOB_STOP, g, JOB_FAIL, false, NULL, &j) == -EEXIST);
 
         printf("Test8: (Mergeable job type, fail)\n");
-        assert_se(manager_add_job(m, JOB_RESTART, g, JOB_FAIL, false, &j) == 0);
+        assert_se(manager_add_job(m, JOB_RESTART, g, JOB_FAIL, false, NULL, &j) == 0);
         manager_dump_jobs(m, stdout, "\t");
 
         printf("Test9: (Unmeargable job type, replace)\n");
-        assert_se(manager_add_job(m, JOB_STOP, g, JOB_REPLACE, false, &j) == 0);
+        assert_se(manager_add_job(m, JOB_STOP, g, JOB_REPLACE, false, NULL, &j) == 0);
         manager_dump_jobs(m, stdout, "\t");
 
         printf("Load4:\n");
-        assert_se(manager_load_unit(m, "h.service", NULL, &h) >= 0);
+        assert_se(manager_load_unit(m, "h.service", NULL, NULL, &h) >= 0);
         manager_dump_units(m, stdout, "\t");
 
         printf("Test10: (Unmeargable job type of auxiliary job, fail)\n");
-        assert_se(manager_add_job(m, JOB_START, h, JOB_FAIL, false, &j) == 0);
+        assert_se(manager_add_job(m, JOB_START, h, JOB_FAIL, false, NULL, &j) == 0);
         manager_dump_jobs(m, stdout, "\t");
 
         manager_free(m);
diff --git a/src/timer.c b/src/timer.c
index b4521e6efc..1c7010d120 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -26,6 +26,7 @@
 #include "timer.h"
 #include "dbus-timer.h"
 #include "special.h"
+#include "bus-errors.h"
 
 static const UnitActiveState state_translation_table[_TIMER_STATE_MAX] = {
         [TIMER_DEAD] = UNIT_INACTIVE,
@@ -261,18 +262,23 @@ fail:
 }
 
 static void timer_enter_running(Timer *t) {
+        DBusError error;
         int r;
+
         assert(t);
+        dbus_error_init(&error);
 
-        if ((r = manager_add_job(t->meta.manager, JOB_START, t->unit, JOB_REPLACE, true, NULL)) < 0)
+        if ((r = manager_add_job(t->meta.manager, JOB_START, t->unit, JOB_REPLACE, true, &error, NULL)) < 0)
                 goto fail;
 
         timer_set_state(t, TIMER_RUNNING);
         return;
 
 fail:
-        log_warning("%s failed to queue unit startup job: %s", t->meta.id, strerror(-r));
+        log_warning("%s failed to queue unit startup job: %s", t->meta.id, bus_error(&error, r));
         timer_enter_dead(t, false);
+
+        dbus_error_free(&error);
 }
 
 static int timer_start(Unit *u) {
diff --git a/src/unit.c b/src/unit.c
index 1874cdf78d..a5f8712ae6 100644
--- a/src/unit.c
+++ b/src/unit.c
@@ -881,7 +881,7 @@ static void unit_check_uneeded(Unit *u) {
         log_info("Service %s is not needed anymore. Stopping.", u->meta.id);
 
         /* Ok, nobody needs us anymore. Sniff. Then let's commit suicide */
-        manager_add_job(u->meta.manager, JOB_STOP, u, JOB_FAIL, true, NULL);
+        manager_add_job(u->meta.manager, JOB_STOP, u, JOB_FAIL, true, NULL, NULL);
 }
 
 static void retroactively_start_dependencies(Unit *u) {
@@ -893,23 +893,23 @@ static void retroactively_start_dependencies(Unit *u) {
 
         SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRES], i)
                 if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
-                        manager_add_job(u->meta.manager, JOB_START, other, JOB_REPLACE, true, NULL);
+                        manager_add_job(u->meta.manager, JOB_START, other, JOB_REPLACE, true, NULL, NULL);
 
         SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRES_OVERRIDABLE], i)
                 if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
-                        manager_add_job(u->meta.manager, JOB_START, other, JOB_FAIL, false, NULL);
+                        manager_add_job(u->meta.manager, JOB_START, other, JOB_FAIL, false, NULL, NULL);
 
         SET_FOREACH(other, u->meta.dependencies[UNIT_REQUISITE], i)
                 if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
-                        manager_add_job(u->meta.manager, JOB_START, other, JOB_REPLACE, true, NULL);
+                        manager_add_job(u->meta.manager, JOB_START, other, JOB_REPLACE, true, NULL, NULL);
 
         SET_FOREACH(other, u->meta.dependencies[UNIT_WANTS], i)
                 if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
-                        manager_add_job(u->meta.manager, JOB_START, other, JOB_FAIL, false, NULL);
+                        manager_add_job(u->meta.manager, JOB_START, other, JOB_FAIL, false, NULL, NULL);
 
         SET_FOREACH(other, u->meta.dependencies[UNIT_CONFLICTS], i)
                 if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
-                        manager_add_job(u->meta.manager, JOB_STOP, other, JOB_REPLACE, true, NULL);
+                        manager_add_job(u->meta.manager, JOB_STOP, other, JOB_REPLACE, true, NULL, NULL);
 }
 
 static void retroactively_stop_dependencies(Unit *u) {
@@ -923,7 +923,7 @@ static void retroactively_stop_dependencies(Unit *u) {
                 /* Pull down units need us recursively if enabled */
                 SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRED_BY], i)
                         if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
-                                manager_add_job(u->meta.manager, JOB_STOP, other, JOB_REPLACE, true, NULL);
+                                manager_add_job(u->meta.manager, JOB_STOP, other, JOB_REPLACE, true, NULL, NULL);
         }
 
         /* Garbage collect services that might not be needed anymore, if enabled */
@@ -1391,7 +1391,7 @@ int unit_add_dependency_by_name(Unit *u, UnitDependency d, const char *name, con
         if (!(name = resolve_template(u, name, path, &s)))
                 return -ENOMEM;
 
-        if ((r = manager_load_unit(u->meta.manager, name, path, &other)) < 0)
+        if ((r = manager_load_unit(u->meta.manager, name, path, NULL, &other)) < 0)
                 goto finish;
 
         r = unit_add_dependency(u, d, other, add_reference);
@@ -1412,7 +1412,7 @@ int unit_add_two_dependencies_by_name(Unit *u, UnitDependency d, UnitDependency
         if (!(name = resolve_template(u, name, path, &s)))
                 return -ENOMEM;
 
-        if ((r = manager_load_unit(u->meta.manager, name, path, &other)) < 0)
+        if ((r = manager_load_unit(u->meta.manager, name, path, NULL, &other)) < 0)
                 goto finish;
 
         r = unit_add_two_dependencies(u, d, e, other, add_reference);
@@ -1433,7 +1433,7 @@ int unit_add_dependency_by_name_inverse(Unit *u, UnitDependency d, const char *n
         if (!(name = resolve_template(u, name, path, &s)))
                 return -ENOMEM;
 
-        if ((r = manager_load_unit(u->meta.manager, name, path, &other)) < 0)
+        if ((r = manager_load_unit(u->meta.manager, name, path, NULL, &other)) < 0)
                 goto finish;
 
         r = unit_add_dependency(other, d, u, add_reference);
@@ -1454,7 +1454,7 @@ int unit_add_two_dependencies_by_name_inverse(Unit *u, UnitDependency d, UnitDep
         if (!(name = resolve_template(u, name, path, &s)))
                 return -ENOMEM;
 
-        if ((r = manager_load_unit(u->meta.manager, name, path, &other)) < 0)
+        if ((r = manager_load_unit(u->meta.manager, name, path, NULL, &other)) < 0)
                 goto finish;
 
         if ((r = unit_add_two_dependencies(other, d, e, u, add_reference)) < 0)
@@ -1682,7 +1682,7 @@ int unit_load_related_unit(Unit *u, const char *type, Unit **_found) {
 
         assert(!unit_has_name(u, t));
 
-        r = manager_load_unit(u->meta.manager, t, NULL, _found);
+        r = manager_load_unit(u->meta.manager, t, NULL, NULL, _found);
         free(t);
 
         assert(r < 0 || *_found != u);
@@ -1967,7 +1967,7 @@ int unit_add_node_link(Unit *u, const char *what, bool wants) {
         if (!(e = unit_name_build_escape(what+1, NULL, ".device")))
                 return -ENOMEM;
 
-        r = manager_load_unit(u->meta.manager, e, NULL, &device);
+        r = manager_load_unit(u->meta.manager, e, NULL, NULL, &device);
         free(e);
 
         if (r < 0)
@@ -1993,7 +1993,7 @@ int unit_coldplug(Unit *u) {
                         return r;
 
         if (u->meta.deserialized_job >= 0) {
-                if ((r = manager_add_job(u->meta.manager, u->meta.deserialized_job, u, JOB_FAIL, false, NULL)) < 0)
+                if ((r = manager_add_job(u->meta.manager, u->meta.deserialized_job, u, JOB_FAIL, false, NULL, NULL)) < 0)
                         return r;
 
                 u->meta.deserialized_job = _JOB_TYPE_INVALID;