journalctl: add new --flush command and make use of it in systemd-journal-flush.service

This new command will ask the journal daemon to flush all log data
stored in /run to /var, and wait for it to complete. This is useful, so
that in case of Storage=persistent we can order systemd-tmpfiles-setup
afterwards, to ensure any possibly newly created directory in /var/log
gets proper access mode and owners.

man/journalctl.xml

@@ -878,6 +878,20 @@
                                 operation.</para></listitem>
                         </varlistentry>
 
+                        <varlistentry>
+                                <term><option>--flush</option></term>
+
+                                <listitem><para>Asks the Journal
+                                daemon to flush any log data stored in
+                                <filename>/run/systemd/log</filename>
+                                into
+                                <filename>/var/systemd/log</filename>,
+                                if persistent storage is enabled. This
+                                call does not return until the
+                                operation is
+                                complete.</para></listitem>
+                        </varlistentry>
+
                         <xi:include href="standard-options.xml" xpointer="help" />
                         <xi:include href="standard-options.xml" xpointer="version" />
                         <xi:include href="standard-options.xml" xpointer="no-pager" />

src/journal/journalctl.c

@@ -31,8 +31,10 @@
 #include <time.h>
 #include <getopt.h>
 #include <signal.h>
+#include <poll.h>
 #include <sys/stat.h>
 #include <sys/ioctl.h>
+#include <sys/inotify.h>
 #include <linux/fs.h>
 
 #ifdef HAVE_ACL
@@ -40,7 +42,8 @@
 #include "acl-util.h"
 #endif
 
-#include "systemd/sd-journal.h"
+#include "sd-journal.h"
+#include "sd-bus.h"
 
 #include "log.h"
 #include "logs-show.h"
@@ -59,6 +62,9 @@
 #include "fsprg.h"
 #include "unit-name.h"
 #include "catalog.h"
+#include "mkdir.h"
+#include "bus-util.h"
+#include "bus-error.h"
 
 #define DEFAULT_FSS_INTERVAL_USEC (15*USEC_PER_MINUTE)
 
@@ -117,6 +123,7 @@ static enum {
         ACTION_DUMP_CATALOG,
         ACTION_UPDATE_CATALOG,
         ACTION_LIST_BOOTS,
+        ACTION_FLUSH,
 } arg_action = ACTION_SHOW;
 
 typedef struct boot_id_t {
@@ -231,6 +238,7 @@ static void help(void) {
                "     --list-catalog        Show message IDs of all entries in the message catalog\n"
                "     --dump-catalog        Show entries in the message catalog\n"
                "     --update-catalog      Update the message catalog database\n"
+               "     --flush               Flush all journal data from /run into /var\n"
 #ifdef HAVE_GCRYPT
                "     --setup-keys          Generate a new FSS key pair\n"
                "     --verify              Verify journal file consistency\n"
@@ -267,6 +275,7 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_UPDATE_CATALOG,
                 ARG_FORCE,
                 ARG_UTC,
+                ARG_FLUSH,
         };
 
         static const struct option options[] = {
@@ -317,6 +326,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "reverse",        no_argument,       NULL, 'r'                },
                 { "machine",        required_argument, NULL, 'M'                },
                 { "utc",            no_argument,       NULL, ARG_UTC            },
+                { "flush",          no_argument,       NULL, ARG_FLUSH          },
                 {}
         };
 
@@ -661,6 +671,10 @@ static int parse_argv(int argc, char *argv[]) {
                         arg_utc = true;
                         break;
 
+                case ARG_FLUSH:
+                        arg_action = ACTION_FLUSH;
+                        break;
+
                 case '?':
                         return -EINVAL;
 
@@ -1641,6 +1655,77 @@ static int access_check(sd_journal *j) {
         return r;
 }
 
+static int flush_to_var(void) {
+        _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
+        _cleanup_bus_close_unref_ sd_bus *bus = NULL;
+        _cleanup_close_ int watch_fd = -1;
+        int r;
+
+        /* Quick exit */
+        if (access("/run/systemd/journal/flushed", F_OK) >= 0)
+                return 0;
+
+        /* OK, let's actually do the full logic, send SIGUSR1 to the
+         * daemon and set up inotify to wait for the flushed file to appear */
+        r = bus_open_system_systemd(&bus);
+        if (r < 0) {
+                log_error("Failed to get D-Bus connection: %s", strerror(-r));
+                return r;
+        }
+
+        r = sd_bus_call_method(
+                        bus,
+                        "org.freedesktop.systemd1",
+                        "/org/freedesktop/systemd1",
+                        "org.freedesktop.systemd1.Manager",
+                        "KillUnit",
+                        &error,
+                        NULL,
+                        "ssi", "systemd-journald.service", "main", SIGUSR1);
+        if (r < 0) {
+                log_error("Failed to kill journal service: %s", bus_error_message(&error, r));
+                return r;
+        }
+
+        mkdir_p("/run/systemd/journal", 0755);
+
+        watch_fd = inotify_init1(IN_NONBLOCK|IN_CLOEXEC);
+        if (watch_fd < 0) {
+                log_error("Failed to create inotify watch: %m");
+                return -errno;
+        }
+
+        r = inotify_add_watch(watch_fd, "/run/systemd/journal", IN_CREATE|IN_DONT_FOLLOW|IN_ONLYDIR);
+        if (r < 0) {
+                log_error("Failed to watch journal directory: %m");
+                return -errno;
+        }
+
+        for (;;) {
+                if (access("/run/systemd/journal/flushed", F_OK) >= 0)
+                        break;
+
+                if (errno != ENOENT) {
+                        log_error("Failed to check for existance of /run/systemd/journal/flushed: %m");
+                        return -errno;
+                }
+
+                r = fd_wait_for_event(watch_fd, POLLIN, USEC_INFINITY);
+                if (r < 0) {
+                        log_error("Failed to wait for event: %s", strerror(-r));
+                        return r;
+                }
+
+                r = flush_fd(watch_fd);
+                if (r < 0) {
+                        log_error("Failed to flush inotify events: %s", strerror(-r));
+                        return r;
+                }
+        }
+
+        return 0;
+}
+
 int main(int argc, char *argv[]) {
         int r;
         _cleanup_journal_close_ sd_journal *j = NULL;
@@ -1665,6 +1750,11 @@ int main(int argc, char *argv[]) {
                 goto finish;
         }
 
+        if (arg_action == ACTION_FLUSH) {
+                r = flush_to_var();
+                goto finish;
+        }
+
         if (arg_action == ACTION_SETUP_KEYS) {
                 r = setup_keys();
                 goto finish;

src/journal/journald-server.c

@@ -1221,11 +1221,12 @@ static int dispatch_sigusr1(sd_event_source *es, const struct signalfd_siginfo *
 
         log_info("Received request to flush runtime journal from PID %"PRIu32, si->ssi_pid);
 
-        touch("/run/systemd/journal/flushed");
         server_flush_to_var(s);
         server_sync(s);
         server_vacuum(s);
 
+        touch("/run/systemd/journal/flushed");
+
         return 0;
 }
 

units/systemd-journal-flush.service.in

@@ -11,8 +11,9 @@ Documentation=man:systemd-journald.service(8) man:journald.conf(5)
 DefaultDependencies=no
 Requires=systemd-journald.service
 After=systemd-journald.service local-fs.target remote-fs.target
-Before=systemd-user-sessions.service
+Before=systemd-user-sessions.service systemd-tmpfiles-setup.service
 
 [Service]
-ExecStart=@rootbindir@/systemctl kill --kill-who=main --signal=SIGUSR1 systemd-journald.service
+ExecStart=@rootbindir@/journalctl --flush
 Type=oneshot
+RemainAfterExit=yes