systemctl: add commands set-default and get-default

systemctl set-default NAME links the default.target to the given unit,
get-default prints out the path to the currently set default target.

man/systemctl.xml

@@ -997,6 +997,24 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
         </listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><command>get-default</command></term>
+
+        <listitem>
+          <para>Get the default target specified
+          via <filename>default.target</filename> link.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><command>set-default <replaceable>NAME</replaceable></command></term>
+
+        <listitem>
+          <para>Set the default target to boot into. Command links
+          <filename>default.target</filename> to the given unit.</para>
+        </listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><command>load <replaceable>NAME</replaceable>...</command></term>
 

shell-completion/bash/systemctl

@@ -134,9 +134,10 @@ _systemctl () {
                [STANDALONE]='daemon-reexec daemon-reload default dump
                              emergency exit halt hibernate hybrid-sleep kexec list-jobs
                              list-units list-unit-files poweroff reboot rescue
-                             show-environment suspend'
+                             show-environment suspend get-default'
                      [NAME]='snapshot load'
                      [FILE]='link'
+                  [TARGETS]='set-default'
         )
 
         for ((i=0; $i <= $COMP_CWORD; i++)); do
@@ -210,6 +211,9 @@ _systemctl () {
         elif __contains_word "$verb" ${VERBS[FILE]}; then
                 comps=$( compgen -A file -- "$cur" )
                 compopt -o filenames
+        elif __contains_word "$verb" ${VERBS[TARGETS]}; then
+                comps=$( __systemctl $mode list-unit-files --type target --full --all \
+                        | { while read -r a b; do echo " $a"; done; } )
         fi
 
         COMPREPLY=( $(compgen -W '$comps' -- "$cur") )

src/core/dbus-manager.c

@@ -227,6 +227,13 @@
         "   <arg name=\"files\" type=\"as\" direction=\"in\"/>\n"       \
         "   <arg name=\"runtime\" type=\"b\" direction=\"in\"/>\n"      \
         "   <arg name=\"changes\" type=\"a(sss)\" direction=\"out\"/>\n" \
+        "  </method>\n"                                                 \
+        "  <method name=\"SetDefaultTarget\">\n"                         \
+        "   <arg name=\"files\" type=\"as\" direction=\"in\"/>\n"       \
+        "   <arg name=\"changes\" type=\"a(sss)\" direction=\"out\"/>\n" \
+        "  </method>\n"                                                 \
+        "  <method name=\"GetDefaultTarget\">\n"                         \
+        "   <arg name=\"name\" type=\"s\" direction=\"out\"/>\n" \
         "  </method>\n"
 
 #define BUS_MANAGER_INTERFACE_SIGNALS                                   \
@@ -1728,7 +1735,8 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
                    dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "ReenableUnitFiles") ||
                    dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "LinkUnitFiles") ||
                    dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "PresetUnitFiles") ||
-                   dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "MaskUnitFiles")) {
+                   dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "MaskUnitFiles") ||
+                   dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "SetDefaultTarget")) {
 
                 char **l = NULL;
                 DBusMessageIter iter;
@@ -1771,6 +1779,8 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
                         carries_install_info = r;
                 } else if (streq(member, "MaskUnitFiles"))
                         r = unit_file_mask(scope, runtime, NULL, l, force, &changes, &n_changes);
+                else if (streq(member, "SetDefaultTarget"))
+                        r = unit_file_set_default(scope, NULL, l[0], &changes, &n_changes);
                 else
                         assert_not_reached("Uh? Wrong method");
 
@@ -1838,6 +1848,22 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
                 if (!reply)
                         goto oom;
 
+        } else if (dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "GetDefaultTarget")) {
+                UnitFileScope scope = m->running_as == SYSTEMD_SYSTEM ? UNIT_FILE_SYSTEM : UNIT_FILE_USER;
+                _cleanup_free_ char *default_target = NULL;
+
+                reply = dbus_message_new_method_return(message);
+                if (!reply)
+                        goto oom;
+
+                r = unit_file_get_default(scope, NULL, &default_target);
+
+                if (r < 0)
+                        return bus_send_error_reply(connection, message, NULL, r);
+
+                if (!dbus_message_append_args(reply, DBUS_TYPE_STRING, &default_target, DBUS_TYPE_INVALID)) {
+                        goto oom;
+                }
         } else {
                 const BusBoundProperties bps[] = {
                         { "org.freedesktop.systemd1.Manager", bus_systemd_properties, systemd_property_string },

src/core/org.freedesktop.systemd1.conf

@@ -86,6 +86,10 @@
                        send_interface="org.freedesktop.systemd1.Manager"
                        send_member="Dump"/>
 
+                <allow send_destination="org.freedesktop.systemd1"
+                       send_interface="org.freedesktop.systemd1.Manager"
+                       send_member="GetDefaultTarget"/>
+
                 <allow receive_sender="org.freedesktop.systemd1"/>
         </policy>
 

src/shared/install.c

@@ -1570,6 +1570,92 @@ int unit_file_reenable(
         return r;
 }
 
+int unit_file_set_default(
+                UnitFileScope scope,
+                const char *root_dir,
+                char *file,
+                UnitFileChange **changes,
+                unsigned *n_changes) {
+
+        _cleanup_lookup_paths_free_ LookupPaths paths = {};
+        _cleanup_install_context_done_ InstallContext c = {};
+        _cleanup_free_ char *config_path = NULL;
+        char *path;
+        int r;
+        InstallInfo *i = NULL;
+
+        assert(scope >= 0);
+        assert(scope < _UNIT_FILE_SCOPE_MAX);
+
+        if (unit_name_to_type(file) != UNIT_TARGET)
+                return -EINVAL;
+
+        r = lookup_paths_init_from_scope(&paths, scope);
+        if (r < 0)
+                return r;
+
+        r = get_config_path(scope, false, root_dir, &config_path);
+        if (r < 0)
+                return r;
+
+        r = install_info_add_auto(&c, file);
+        if (r < 0)
+                return r;
+
+        i = (InstallInfo*)hashmap_first(c.will_install);
+
+        r = unit_file_search(&c, i, &paths, root_dir, false);
+        if (r < 0)
+                return r;
+
+        path = strappenda(config_path, "/default.target");
+        r = create_symlink(i->path, path, true, changes, n_changes);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int unit_file_get_default(
+                UnitFileScope scope,
+                const char *root_dir,
+                char **name) {
+
+        _cleanup_lookup_paths_free_ LookupPaths paths = {};
+        char **p;
+        int r;
+
+        r = lookup_paths_init_from_scope(&paths, scope);
+        if (r < 0)
+                return r;
+
+        STRV_FOREACH(p, paths.unit_path) {
+                _cleanup_free_ char *path = NULL, *tmp = NULL;
+
+                if (isempty(root_dir))
+                        path = strappend(*p, "/default.target");
+                else
+                        path = strjoin(root_dir, "/", *p, "/default.target", NULL);
+
+                if (!path)
+                        return -ENOMEM;
+
+                r = readlink_malloc(path, &tmp);
+                if (r == -ENOENT)
+                        continue;
+                else if (r < 0)
+                        return r;
+
+                *name = strdup(path_get_file_name(tmp));
+                if (!*name)
+                        return -ENOMEM;
+
+                return 0;
+        }
+
+        return -ENOENT;
+}
+
 UnitFileState unit_file_get_state(
                 UnitFileScope scope,
                 const char *root_dir,

src/shared/install.h

@@ -80,6 +80,8 @@ int unit_file_link(UnitFileScope scope, bool runtime, const char *root_dir, char
 int unit_file_preset(UnitFileScope scope, bool runtime, const char *root_dir, char *files[], bool force, UnitFileChange **changes, unsigned *n_changes);
 int unit_file_mask(UnitFileScope scope, bool runtime, const char *root_dir, char *files[], bool force, UnitFileChange **changes, unsigned *n_changes);
 int unit_file_unmask(UnitFileScope scope, bool runtime, const char *root_dir, char *files[], UnitFileChange **changes, unsigned *n_changes);
+int unit_file_set_default(UnitFileScope scope, const char *root_dir, char *file, UnitFileChange **changes, unsigned *n_changes);
+int unit_file_get_default(UnitFileScope scope, const char *root_dir, char **name);
 
 UnitFileState unit_file_get_state(UnitFileScope scope, const char *root_dir, const char *filename);
 

src/systemctl/systemctl.c

@@ -1177,6 +1177,59 @@ static int list_dependencies(DBusConnection *bus, char **args) {
         return list_dependencies_one(bus, u, 0, &units, 0);
 }
 
+static int get_default(DBusConnection *bus, char **args) {
+        char *path = NULL;
+        _cleanup_dbus_message_unref_ DBusMessage *m = NULL, *reply = NULL;
+        int r;
+        _cleanup_dbus_error_free_ DBusError error;
+
+        dbus_error_init(&error);
+
+        if (!bus || avoid_bus()) {
+                r = unit_file_get_default(arg_scope, arg_root, &path);
+
+                if (r < 0) {
+                        log_error("Operation failed: %s", strerror(-r));
+                        goto finish;
+                }
+
+                r = 0;
+        } else {
+                r = bus_method_call_with_reply(
+                        bus,
+                        "org.freedesktop.systemd1",
+                        "/org/freedesktop/systemd1",
+                        "org.freedesktop.systemd1.Manager",
+                        "GetDefaultTarget",
+                        &reply,
+                        NULL,
+                        DBUS_TYPE_INVALID);
+
+                if (r < 0) {
+                        log_error("Operation failed: %s", strerror(-r));
+                        goto finish;
+                }
+
+                if (!dbus_message_get_args(reply, &error,
+                                   DBUS_TYPE_STRING, &path,
+                                   DBUS_TYPE_INVALID)) {
+                        log_error("Failed to parse reply: %s", bus_error_message(&error));
+                        dbus_error_free(&error);
+                        return  -EIO;
+                }
+        }
+
+        if (path)
+                printf("%s\n", path);
+
+finish:
+        if ((!bus || avoid_bus()) && path)
+                free(path);
+
+        return r;
+
+}
+
 struct job_info {
         uint32_t id;
         char *name, *type, *state;
@@ -4243,6 +4296,8 @@ static int enable_unit(DBusConnection *bus, char **args) {
                         r = unit_file_mask(arg_scope, arg_runtime, arg_root, mangled_names, arg_force, &changes, &n_changes);
                 else if (streq(verb, "unmask"))
                         r = unit_file_unmask(arg_scope, arg_runtime, arg_root, mangled_names, &changes, &n_changes);
+                else if (streq(verb, "set-default"))
+                        r = unit_file_set_default(arg_scope, arg_root, args[1], &changes, &n_changes);
                 else
                         assert_not_reached("Unknown verb");
 
@@ -4286,6 +4341,8 @@ static int enable_unit(DBusConnection *bus, char **args) {
                 else if (streq(verb, "unmask")) {
                         method = "UnmaskUnitFiles";
                         send_force = false;
+                } else if (streq(verb, "set-default")) {
+                        method = "SetDefaultTarget";
                 } else
                         assert_not_reached("Unknown verb");
 
@@ -4585,6 +4642,8 @@ static int systemctl_help(void) {
                "  unmask [NAME...]                Unmask one or more units\n"
                "  link [PATH...]                  Link one or more units files into\n"
                "                                  the search path\n"
+               "  get-default                     Get the name of the default target\n"
+               "  set-default NAME                Set the default target\n"
                "  is-enabled [NAME...]            Check whether unit files are enabled\n\n"
                "Job Commands:\n"
                "  list-jobs                       List jobs\n"
@@ -5646,6 +5705,8 @@ static int systemctl_main(DBusConnection *bus, int argc, char *argv[], DBusError
                 { "link",                  MORE,  2, enable_unit       },
                 { "switch-root",           MORE,  2, switch_root       },
                 { "list-dependencies",     LESS,  2, list_dependencies },
+                { "set-default",           EQUAL, 2, enable_unit       },
+                { "get-default",           LESS,  1, get_default       },
         };
 
         int left;
@@ -5717,7 +5778,9 @@ static int systemctl_main(DBusConnection *bus, int argc, char *argv[], DBusError
             !streq(verbs[i].verb, "preset") &&
             !streq(verbs[i].verb, "mask") &&
             !streq(verbs[i].verb, "unmask") &&
-            !streq(verbs[i].verb, "link")) {
+            !streq(verbs[i].verb, "link") &&
+            !streq(verbs[i].verb, "set-default") &&
+            !streq(verbs[i].verb, "get-default")) {
 
                 if (running_in_chroot() > 0) {
                         log_info("Running in chroot, ignoring request.");