systemctl: add edit verb

It helps editing units by either creating a drop-in file, like
/etc/systemd/system/my.service.d/override.conf, or by copying the
original unit from /usr/lib/systemd/ to /etc/systemd/ if the --full
option is specified.

It invokes an editor on temporary files related to the unit files and
if the editor exited successfully, then it renames the temporary files
to their original names (e.g. my.service or override.conf) and
daemon-reload is invoked.

If the temporary file is empty the modification is canceled.

See https://bugzilla.redhat.com/show_bug.cgi?id=906824

1 files changed, 519 insertions, 3 deletions

diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index ffb97df14..47b0aac03 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -73,6 +73,8 @@
 #include "bus-message.h"
 #include "bus-error.h"
 #include "bus-errors.h"
+#include "copy.h"
+#include "mkdir.h"
 
 static char **arg_types = NULL;
 static char **arg_states = NULL;
@@ -5707,6 +5709,517 @@ static int is_system_running(sd_bus *bus, char **args) {
         return streq(state, "running") ? EXIT_SUCCESS : EXIT_FAILURE;
 }
 
+static int unit_file_find_path(LookupPaths *lp, const char *unit_name, char **unit_path) {
+        char **p;
+
+        assert(lp);
+        assert(unit_name);
+        assert(unit_path);
+
+        STRV_FOREACH(p, lp->unit_path) {
+                char *path;
+
+                path = path_join(arg_root, *p, unit_name);
+                if (!path)
+                        return log_oom();
+
+                if (access(path, F_OK) == 0) {
+                        *unit_path = path;
+                        return 1;
+                }
+
+                free(path);
+        }
+
+        return 0;
+}
+
+static int create_edit_temp_file(const char *new_path, const char *original_path, char **ret_tmp_fn) {
+        _cleanup_close_ int fd = -1;
+        int r;
+        char *t;
+
+        assert(new_path);
+        assert(original_path);
+        assert(ret_tmp_fn);
+
+        t = tempfn_random(new_path);
+        if (!t)
+                return log_oom();
+
+        r = mkdir_parents(new_path, 0755);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create directories for %s: %m", new_path);
+
+        r = copy_file(original_path, t, 0, 0644);
+        if (r == -ENOENT) {
+                r = touch(t);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to create temporary file %s: %m", t);
+                        free(t);
+                        return r;
+                }
+        } else if (r < 0) {
+                log_error_errno(r, "Failed to copy %s to %s: %m", original_path, t);
+                free(t);
+                return r;
+        }
+
+        *ret_tmp_fn = t;
+
+        return 0;
+}
+
+static int get_drop_in_to_edit(const char *unit_name, const char *user_home, const char *user_runtime, char **ret_path) {
+        char *tmp_new_path;
+        char *tmp;
+
+        assert(unit_name);
+        assert(ret_path);
+
+        switch (arg_scope) {
+                case UNIT_FILE_SYSTEM:
+                        tmp = strappenda(arg_runtime ? "/run/systemd/system/" : SYSTEM_CONFIG_UNIT_PATH "/", unit_name, ".d/override.conf");
+                        break;
+                case UNIT_FILE_GLOBAL:
+                        tmp = strappenda(arg_runtime ? "/run/systemd/user/" : USER_CONFIG_UNIT_PATH "/", unit_name, ".d/override.conf");
+                        break;
+                case UNIT_FILE_USER:
+                        assert(user_home);
+                        assert(user_runtime);
+
+                        tmp = strappenda(arg_runtime ? user_runtime : user_home, "/", unit_name, ".d/override.conf");
+                        break;
+                default:
+                        assert_not_reached("Invalid scope");
+        }
+
+        tmp_new_path = path_join(arg_root, tmp, NULL);
+        if (!tmp_new_path)
+                return log_oom();
+
+        *ret_path = tmp_new_path;
+
+        return 0;
+}
+
+static int unit_file_create_drop_in(const char *unit_name, const char *user_home, const char *user_runtime, char **ret_new_path, char **ret_tmp_path) {
+        char *tmp_new_path;
+        char *tmp_tmp_path;
+        int r;
+
+        assert(unit_name);
+        assert(ret_new_path);
+        assert(ret_tmp_path);
+
+        r = get_drop_in_to_edit(unit_name, user_home, user_runtime, &tmp_new_path);
+        if (r < 0)
+                return r;
+
+        r = create_edit_temp_file(tmp_new_path, tmp_new_path, &tmp_tmp_path);
+        if (r < 0) {
+                free(tmp_new_path);
+                return r;
+        }
+
+        *ret_new_path = tmp_new_path;
+        *ret_tmp_path = tmp_tmp_path;
+
+        return 0;
+}
+
+static bool unit_is_editable(const char *unit_name, const char *fragment_path, const char *user_home) {
+        bool editable = true;
+        const char *invalid_path;
+
+        assert(unit_name);
+
+        if (!arg_runtime)
+                return true;
+
+        switch (arg_scope) {
+                case UNIT_FILE_SYSTEM:
+                        if (path_startswith(fragment_path, "/etc/systemd/system")) {
+                                editable = false;
+                                invalid_path = "/etc/systemd/system";
+                        } else if (path_startswith(fragment_path, SYSTEM_CONFIG_UNIT_PATH)) {
+                                editable = false;
+                                invalid_path = SYSTEM_CONFIG_UNIT_PATH;
+                        }
+                        break;
+                case UNIT_FILE_GLOBAL:
+                        if (path_startswith(fragment_path, "/etc/systemd/user")) {
+                                editable = false;
+                                invalid_path = "/etc/systemd/user";
+                        } else if (path_startswith(fragment_path, USER_CONFIG_UNIT_PATH)) {
+                                editable = false;
+                                invalid_path = USER_CONFIG_UNIT_PATH;
+                        }
+                        break;
+                case UNIT_FILE_USER:
+                        assert(user_home);
+
+                        if (path_startswith(fragment_path, "/etc/systemd/user")) {
+                                editable = false;
+                                invalid_path = "/etc/systemd/user";
+                        } else if (path_startswith(fragment_path, USER_CONFIG_UNIT_PATH)) {
+                                editable = false;
+                                invalid_path = USER_CONFIG_UNIT_PATH;
+                        } else if (path_startswith(fragment_path, user_home)) {
+                                editable = false;
+                                invalid_path = user_home;
+                        }
+                        break;
+                default:
+                        assert_not_reached("Invalid scope");
+        }
+
+        if (!editable)
+                log_error("%s ignored: cannot temporarily edit units from %s", unit_name, invalid_path);
+
+        return editable;
+}
+
+static int get_copy_to_edit(const char *unit_name, const char *fragment_path, const char *user_home, const char *user_runtime, char **ret_path) {
+        char *tmp_new_path;
+
+        assert(unit_name);
+        assert(ret_path);
+
+        if (!unit_is_editable(unit_name, fragment_path, user_home))
+                return -EINVAL;
+
+        switch (arg_scope) {
+                case UNIT_FILE_SYSTEM:
+                        tmp_new_path = path_join(arg_root, arg_runtime ? "/run/systemd/system/" : SYSTEM_CONFIG_UNIT_PATH, unit_name);
+                        break;
+                case UNIT_FILE_GLOBAL:
+                        tmp_new_path = path_join(arg_root, arg_runtime ? "/run/systemd/user/" : USER_CONFIG_UNIT_PATH, unit_name);
+                        break;
+                case UNIT_FILE_USER:
+                        assert(user_home);
+                        assert(user_runtime);
+
+                        tmp_new_path = path_join(arg_root, arg_runtime ? user_runtime : user_home, unit_name);
+                        break;
+                default:
+                        assert_not_reached("Invalid scope");
+        }
+        if (!tmp_new_path)
+                return log_oom();
+
+        *ret_path = tmp_new_path;
+
+        return 0;
+}
+
+static int unit_file_create_copy(const char *unit_name,
+                                 const char *fragment_path,
+                                 const char *user_home,
+                                 const char *user_runtime,
+                                 char **ret_new_path,
+                                 char **ret_tmp_path) {
+        char *tmp_new_path;
+        char *tmp_tmp_path;
+        int r;
+
+        assert(fragment_path);
+        assert(unit_name);
+        assert(ret_new_path);
+        assert(ret_tmp_path);
+
+        r = get_copy_to_edit(unit_name, fragment_path, user_home, user_runtime, &tmp_new_path);
+        if (r < 0)
+                return r;
+
+        if (!path_equal(fragment_path, tmp_new_path) && access(tmp_new_path, F_OK) == 0) {
+                char response;
+
+                r = ask_char(&response, "yn", "%s already exists, are you sure to overwrite it with %s? [(y)es, (n)o] ", tmp_new_path, fragment_path);
+                if (r < 0) {
+                        free(tmp_new_path);
+                        return r;
+                }
+                if (response != 'y') {
+                        log_warning("%s ignored", unit_name);
+                        free(tmp_new_path);
+                        return -1;
+                }
+        }
+
+        r = create_edit_temp_file(tmp_new_path, fragment_path, &tmp_tmp_path);
+        if (r < 0) {
+                log_error_errno(r, "Failed to create temporary file for %s: %m", tmp_new_path);
+                free(tmp_new_path);
+                return r;
+        }
+
+        *ret_new_path = tmp_new_path;
+        *ret_tmp_path = tmp_tmp_path;
+
+        return 0;
+}
+
+static int run_editor(char **paths) {
+        pid_t pid;
+        int r;
+
+        assert(paths);
+
+        pid = fork();
+        if (pid < 0) {
+                log_error_errno(errno, "Failed to fork: %m");
+                return -errno;
+        }
+
+        if (pid == 0) {
+                const char **args;
+                char **backup_editors = STRV_MAKE("nano", "vim", "vi");
+                char *editor;
+                char **tmp_path, **original_path, **p;
+                unsigned i = 1;
+                size_t argc;
+
+                argc = strv_length(paths)/2 + 1;
+                args = newa(const char*, argc + 1);
+
+                args[0] = NULL;
+                STRV_FOREACH_PAIR(original_path, tmp_path, paths) {
+                        args[i] = *tmp_path;
+                        i++;
+                }
+                args[argc] = NULL;
+
+                /* SYSTEMD_EDITOR takes precedence over EDITOR which takes precedence over VISUAL
+                 * If neither SYSTEMD_EDITOR nor EDITOR nor VISUAL are present,
+                 * we try to execute well known editors
+                 */
+                editor = getenv("SYSTEMD_EDITOR");
+                if (!editor)
+                        editor = getenv("EDITOR");
+                if (!editor)
+                        editor = getenv("VISUAL");
+
+                if (!isempty(editor)) {
+                        args[0] = editor;
+                        execvp(editor, (char* const*) args);
+                }
+
+                STRV_FOREACH(p, backup_editors) {
+                        args[0] = *p;
+                        execvp(*p, (char* const*) args);
+                        /* We do not fail if the editor doesn't exist
+                         * because we want to try each one of them before
+                         * failing.
+                         */
+                        if (errno != ENOENT) {
+                                log_error("Failed to execute %s: %m", editor);
+                                _exit(EXIT_FAILURE);
+                        }
+                }
+
+                log_error("Cannot edit unit(s): No editor available. Please set either SYSTEMD_EDITOR or EDITOR or VISUAL environment variable");
+                _exit(EXIT_FAILURE);
+        }
+
+        r = wait_for_terminate_and_warn("editor", pid, true);
+        if (r < 0)
+                return log_error_errno(r, "Failed to wait for child: %m");
+
+        return r;
+}
+
+static int find_paths_to_edit(sd_bus *bus, char **names, char ***paths) {
+        _cleanup_free_ char *user_home = NULL;
+        _cleanup_free_ char *user_runtime = NULL;
+        char **name;
+        int r;
+
+        assert(names);
+        assert(paths);
+
+        if (arg_scope == UNIT_FILE_USER) {
+                r = user_config_home(&user_home);
+                if (r < 0)
+                        return log_oom();
+                else if (r == 0) {
+                        log_error("Cannot edit units for the user instance: home directory unknown");
+                        return -1;
+                }
+
+                r = user_runtime_dir(&user_runtime);
+                if (r < 0)
+                        return log_oom();
+                else if (r == 0) {
+                        log_error("Cannot edit units for the user instance: runtime directory unknown");
+                        return -1;
+                }
+        }
+
+        if (!bus || avoid_bus()) {
+                _cleanup_lookup_paths_free_ LookupPaths lp = {};
+
+                /* If there is no bus, we try to find the units by testing each available directory
+                 * according to the scope.
+                 */
+                r = lookup_paths_init(&lp,
+                                arg_scope == UNIT_FILE_SYSTEM ? SYSTEMD_SYSTEM : SYSTEMD_USER,
+                                arg_scope == UNIT_FILE_USER,
+                                arg_root,
+                                NULL, NULL, NULL);
+                if (r < 0) {
+                        log_error_errno(r, "Failed get lookup paths: %m");
+                        return r;
+                }
+
+                STRV_FOREACH(name, names) {
+                        _cleanup_free_ char *path = NULL;
+                        char *new_path, *tmp_path;
+
+                        r = unit_file_find_path(&lp, *name, &path);
+                        if (r < 0)
+                                return r;
+                        if (r == 0) {
+                                log_warning("%s ignored: not found", *name);
+                                continue;
+                        }
+
+                        if (arg_full)
+                                r = unit_file_create_copy(*name, path, user_home, user_runtime, &new_path, &tmp_path);
+                        else
+                                r = unit_file_create_drop_in(*name, user_home, user_runtime, &new_path, &tmp_path);
+
+                        if (r < 0)
+                                continue;
+
+                        r = strv_push(paths, new_path);
+                        if (r < 0)
+                                return log_oom();
+
+                        r = strv_push(paths, tmp_path);
+                        if (r < 0)
+                                return log_oom();
+                }
+        } else {
+                STRV_FOREACH(name, names) {
+                        _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
+                        _cleanup_free_ char *fragment_path = NULL;
+                        _cleanup_free_ char *unit = NULL;
+                        char *new_path, *tmp_path;
+
+                        unit = unit_dbus_path_from_name(*name);
+                        if (!unit)
+                                return log_oom();
+
+                        if (need_daemon_reload(bus, *name) > 0) {
+                                log_warning("%s ignored: unit file changed on disk. Run 'systemctl%s daemon-reload'.",
+                                        *name, arg_scope == UNIT_FILE_SYSTEM ? "" : " --user");
+                                continue;
+                        }
+
+                        r = sd_bus_get_property_string(
+                                        bus,
+                                        "org.freedesktop.systemd1",
+                                        unit,
+                                        "org.freedesktop.systemd1.Unit",
+                                        "FragmentPath",
+                                        &error,
+                                        &fragment_path);
+                        if (r < 0) {
+                                log_warning("Failed to get FragmentPath: %s", bus_error_message(&error, r));
+                                continue;
+                        }
+
+                        if (isempty(fragment_path)) {
+                                log_warning("%s ignored: not found", *name);
+                                continue;
+                        }
+
+                        if (arg_full)
+                                r = unit_file_create_copy(*name, fragment_path, user_home, user_runtime, &new_path, &tmp_path);
+                        else
+                                r = unit_file_create_drop_in(*name, user_home, user_runtime, &new_path, &tmp_path);
+                        if (r < 0)
+                                continue;
+
+                        r = strv_push(paths, new_path);
+                        if (r < 0)
+                                return log_oom();
+
+                        r = strv_push(paths, tmp_path);
+                        if (r < 0)
+                                return log_oom();
+                }
+        }
+
+        return 0;
+}
+
+static int edit(sd_bus *bus, char **args) {
+        _cleanup_strv_free_ char **names = NULL;
+        _cleanup_strv_free_ char **paths = NULL;
+        char **original, **tmp;
+        int r;
+
+        assert(args);
+
+        if (!on_tty()) {
+                log_error("Cannot edit units if we are not on a tty");
+                return -EINVAL;
+        }
+
+        if (arg_transport != BUS_TRANSPORT_LOCAL) {
+                log_error("Cannot remotely edit units");
+                return -EINVAL;
+        }
+
+        r = expand_names(bus, args + 1, NULL, &names);
+        if (r < 0)
+                return log_error_errno(r, "Failed to expand names: %m");
+
+        if (!names) {
+                log_error("No unit name found by expanding names");
+                return -ENOENT;
+        }
+
+        r = find_paths_to_edit(bus, names, &paths);
+        if (r < 0)
+                return r;
+
+        if (strv_isempty(paths)) {
+                log_error("Cannot find any units to edit");
+                return -ENOENT;
+        }
+
+        r = run_editor(paths);
+        if (r < 0)
+                goto end;
+
+        STRV_FOREACH_PAIR(original, tmp, paths) {
+                /* If the temporary file is empty we ignore it.
+                 * It's useful if the user wants to cancel its modification
+                 */
+                if (null_or_empty_path(*tmp)) {
+                        log_warning("Edition of %s canceled: temporary file empty", *original);
+                        continue;
+                }
+                r = rename(*tmp, *original);
+                if (r < 0) {
+                        r = log_error_errno(errno, "Failed to rename %s to %s: %m", *tmp, *original);
+                        goto end;
+                }
+        }
+
+        if (!arg_no_reload && bus && !avoid_bus())
+                r = daemon_reload(bus, args);
+
+end:
+        STRV_FOREACH_PAIR(original, tmp, paths)
+                unlink_noerrno(*tmp);
+
+        return r;
+}
+
 static void systemctl_help(void) {
 
         pager_open_if_enabled();
@@ -5804,7 +6317,9 @@ static void systemctl_help(void) {
                "  add-requires TARGET NAME...     Add 'Requires' dependency for the target\n"
                "                                  on specified one or more units\n"
                "  get-default                     Get the name of the default target\n"
-               "  set-default NAME                Set the default target\n\n"
+               "  set-default NAME                Set the default target\n"
+               "  edit NAME...                    Edit one or more unit files\n"
+               "\n"
                "Machine Commands:\n"
                "  list-machines [PATTERN...]      List local containers and host\n\n"
                "Job Commands:\n"
@@ -6813,8 +7328,9 @@ static int systemctl_main(sd_bus *bus, int argc, char *argv[], int bus_error) {
                 { "get-default",           EQUAL, 1, get_default,      NOBUS },
                 { "set-property",          MORE,  3, set_property      },
                 { "is-system-running",     EQUAL, 1, is_system_running },
-                { "add-wants",             MORE,  3, add_dependency,        NOBUS },
-                { "add-requires",          MORE,  3, add_dependency,        NOBUS },
+                { "add-wants",             MORE,  3, add_dependency,   NOBUS },
+                { "add-requires",          MORE,  3, add_dependency,   NOBUS },
+                { "edit",                  MORE,  2, edit,             NOBUS },
                 {}
         }, *verb = verbs;