Make initrd.target the default target in the initrd

First, rename root-fs.target to initrd-root-fs.target to clarify its usage.

Mount units with "x-initrd-rootfs.mount" are now ordered before
initrd-root-fs.target. As we sometimes construct /sysroot mounts in
/etc/fstab in the initrd, we want these to be mounted before the
initrd-root-fs.target is active.

initrd.target can be the default target in the initrd.

                             (normal startup)
                                    :
                                    :
                                    v
                              basic.target
                                    |
             ______________________/|
            /                       |
            |                  sysroot.mount
            |                       |
            |                       v
            |             initrd-root-fs.target
            |                       |
            |                       v
            |            initrd-parse-etc.service
(custom initrd services)            |
            |                       v
            |            (sysroot-usr.mount and
            |             various mounts marked
            |               with fstab option
            |                x-initrd.mount)
            |                       |
            |                       v
            |                initrd-fs.target
            |                       |
            \______________________ |
                                   \|
                                    v
                               initrd.target
                                    |
                                    v
                          initrd-cleanup.service
                               isolates to
                         initrd-switch-root.target
                                    |
                                    v
             ______________________/|
            /                       |
            |        initrd-udevadm-cleanup-db.service
            |                       |
(custom initrd services)            |
            |                       |
            \______________________ |
                                   \|
                                    v
                        initrd-switch-root.target
                                    |
                                    v
                        initrd-switch-root.service
                                    |
                                    v
                               switch-root

11 files changed, 115 insertions, 12 deletions

diff --git a/Makefile.am b/Makefile.am
index 175d14b3ae..cf2154452a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -347,8 +347,9 @@ dist_systemunit_DATA = \
 	units/kexec.target \
 	units/local-fs.target \
 	units/local-fs-pre.target \
+	units/initrd.target \
 	units/initrd-fs.target \
-	units/root-fs.target \
+	units/initrd-root-fs.target \
 	units/remote-fs.target \
 	units/remote-fs-pre.target \
 	units/network.target \
diff --git a/man/bootup.xml b/man/bootup.xml
index f65abf5452..6bd22ef476 100644
--- a/man/bootup.xml
+++ b/man/bootup.xml
@@ -174,6 +174,79 @@
         </refsect1>
 
         <refsect1>
+                <title>Systemd in the Initrd</title>
+                <para>If the initrd creation tool used the services provided
+                by systemd, the default target in the initrd is the
+                initrd-fs.target. The process is the same as above until the basic.target is reached.
+                Systemd now continues to the initrd.target. If the root device could be mounted
+                on /sysroot, the sysroot.mount unit is active and the initrd-root-fs.target is reached.
+                initrd-parse-etc.service scans /sysroot/etc/fstab for the /usr mountpoint and for entries
+                marked with the <emphasis>x-initrd.mount</emphasis> option set. If these mountpoint are
+                mounted in /sysroot, the initrd-fs.target is reached.
+                The initrd-cleanup.service isolates to the initrd-switch-root.target,
+                where cleanup services can run. At the very last end
+                initrd-switch-root.service is activated, which will cause
+                the system to switch root to /sysroot.
+                </para>
+
+<programlisting>
+                                        (same as above)
+                                               :
+                                               :
+                                               v
+                                         basic.target
+                                               |                                 emergency.service
+                        ______________________/|                                         |
+                       /                       |                                         v
+                       |                  sysroot.mount                          <emphasis>emergency.target</emphasis>
+                       |                       |
+                       |                       v
+                       |             initrd-root-fs.target
+                       |                       |
+                       |                       v
+                       |            initrd-parse-etc.service
+           (custom initrd services)            |
+                       |                       v
+                       |            (sysroot-usr.mount and
+                       |             various mounts marked
+                       |               with fstab option
+                       |                x-initrd.mount)
+                       |                       |
+                       |                       v
+                       |                initrd-fs.target
+                       |                       |
+                       \______________________ |
+                                              \|
+                                               v
+                                          initrd.target
+                                               |
+                                               v
+                                     initrd-cleanup.service
+                                          isolates to
+                                    initrd-switch-root.target
+                                               |
+                                               v
+                        ______________________/|
+                       /                       |
+                       |        initrd-udevadm-cleanup-db.service
+                       |                       |
+           (custom initrd services)            |
+                       |                       |
+                       \______________________ |
+                                              \|
+                                               v
+                                   initrd-switch-root.target
+                                               |
+                                               v
+                                   initrd-switch-root.service
+                                               |
+                                               v
+                                          switch-root
+</programlisting>
+        </refsect1>
+
+
+        <refsect1>
                 <title>System Manager Shutdown</title>
 
                 <para>System shutdown also consists of various target
diff --git a/man/systemd.special.xml b/man/systemd.special.xml
index 7b780998fd..67a81b639b 100644
--- a/man/systemd.special.xml
+++ b/man/systemd.special.xml
@@ -79,7 +79,7 @@
                 <filename>remote-fs.target</filename>,
                 <filename>remote-fs-pre.target</filename>,
                 <filename>rescue.target</filename>,
-                <filename>root-fs.target</filename>,
+                <filename>initrd-root-fs.target</filename>,
                 <filename>rpcbind.target</filename>,
                 <filename>runlevel2.target</filename>,
                 <filename>runlevel3.target</filename>,
@@ -523,7 +523,7 @@
                                 </listitem>
                         </varlistentry>
                         <varlistentry>
-                                <term><filename>root-fs.target</filename></term>
+                                <term><filename>initrd-root-fs.target</filename></term>
                                 <listitem>
                                         <para>systemd automatically
                                         adds dependencies of type
diff --git a/src/core/special.h b/src/core/special.h
index 52e593b690..c7b856e2bd 100644
--- a/src/core/special.h
+++ b/src/core/special.h
@@ -49,7 +49,7 @@
 #define SPECIAL_LOCAL_FS_TARGET "local-fs.target"
 #define SPECIAL_LOCAL_FS_PRE_TARGET "local-fs-pre.target"
 #define SPECIAL_INITRD_FS_TARGET "initrd-fs.target"
-#define SPECIAL_ROOT_FS_TARGET "root-fs.target"
+#define SPECIAL_INITRD_ROOT_FS_TARGET "initrd-root-fs.target"
 #define SPECIAL_REMOTE_FS_TARGET "remote-fs.target"       /* LSB's $remote_fs */
 #define SPECIAL_REMOTE_FS_PRE_TARGET "remote-fs-pre.target"
 #define SPECIAL_SWAP_TARGET "swap.target"
diff --git a/src/fstab-generator/fstab-generator.c b/src/fstab-generator/fstab-generator.c
index b4fb1344e6..cf85d3189a 100644
--- a/src/fstab-generator/fstab-generator.c
+++ b/src/fstab-generator/fstab-generator.c
@@ -199,6 +199,12 @@ static bool mount_in_initrd(struct mntent *me) {
                 streq(me->mnt_dir, "/usr");
 }
 
+static bool mount_is_rootfs(struct mntent *me) {
+        assert(me);
+
+        return hasmntopt(me, "x-initrd-rootfs.mount");
+}
+
 static int add_mount(const char *what, const char *where, const char *type, const char *opts,
                      int passno, bool noauto, bool nofail, bool automount, bool isbind,
                      const char *pre, const char *post, const char *source) {
@@ -434,6 +440,9 @@ static int parse_fstab(const char *prefix, bool initrd) {
                         if (initrd) {
                                 post = SPECIAL_INITRD_FS_TARGET;
                                 pre = NULL;
+                        } else if (mount_is_rootfs(me)) {
+                                post = SPECIAL_INITRD_ROOT_FS_TARGET;
+                                pre = NULL;
                         } else if (mount_is_network(me)) {
                                 post = SPECIAL_REMOTE_FS_TARGET;
                                 pre = SPECIAL_REMOTE_FS_PRE_TARGET;
@@ -525,7 +534,7 @@ static int parse_new_root_from_proc_cmdline(void) {
 
         log_debug("Found entry what=%s where=/sysroot type=%s", what, type);
         r = add_mount(what, "/sysroot", type, opts, 0, false, false, false,
-                      false, NULL, SPECIAL_ROOT_FS_TARGET, "/proc/cmdline");
+                      false, NULL, SPECIAL_INITRD_ROOT_FS_TARGET, "/proc/cmdline");
 
         return (r < 0) ? r : 0;
 }
diff --git a/units/initrd-cleanup.service.in b/units/initrd-cleanup.service.in
index 5bef090e08..218ec807ff 100644
--- a/units/initrd-cleanup.service.in
+++ b/units/initrd-cleanup.service.in
@@ -10,8 +10,7 @@ Description=Cleaning Up and Shutting Down Daemons
 DefaultDependencies=no
 ConditionPathExists=/etc/initrd-release
 OnFailure=emergency.target
-Wants=root-fs.target initrd-fs.target
-After=root-fs.target initrd-fs.target
+After=initrd-root-fs.target initrd-fs.target initrd.target
 
 [Service]
 Type=oneshot
diff --git a/units/initrd-fs.target b/units/initrd-fs.target
index 6ba1758e45..7578b8824b 100644
--- a/units/initrd-fs.target
+++ b/units/initrd-fs.target
@@ -11,3 +11,4 @@ Documentation=man:systemd.special(7)
 OnFailure=emergency.target
 OnFailureIsolate=yes
 ConditionPathExists=/etc/initrd-release
+After=initrd-parse-etc.service
diff --git a/units/initrd-parse-etc.service.in b/units/initrd-parse-etc.service.in
index 44fee7bd34..07728e200f 100644
--- a/units/initrd-parse-etc.service.in
+++ b/units/initrd-parse-etc.service.in
@@ -8,13 +8,14 @@
 [Unit]
 Description=Reload Configuration from the Real Root
 DefaultDependencies=no
-Requires=root-fs.target
-After=root-fs.target
+Requires=initrd-root-fs.target
+After=initrd-root-fs.target
 OnFailure=emergency.target
 ConditionPathExists=/etc/initrd-release
 
 [Service]
 Type=oneshot
 ExecStartPre=@rootbindir@/systemctl daemon-reload
-ExecStart=@rootbindir@/systemctl start initrd-fs.target
+# we have to retrigger initrd-fs.target after daemon-reload
+ExecStart=-@rootbindir@/systemctl --no-block start initrd-fs.target
 ExecStart=@rootbindir@/systemctl --no-block start initrd-cleanup.service
diff --git a/units/root-fs.target b/units/initrd-root-fs.target
index 13515341eb..cd189f0296 100644
--- a/units/root-fs.target
+++ b/units/initrd-root-fs.target
@@ -9,3 +9,5 @@
 Description=Initrd Root File System
 Documentation=man:systemd.special(7)
 ConditionPathExists=/etc/initrd-release
+OnFailure=emergency.target
+OnFailureIsolate=yes
diff --git a/units/initrd-switch-root.target b/units/initrd-switch-root.target
index cf646c4ef9..f34768790b 100644
--- a/units/initrd-switch-root.target
+++ b/units/initrd-switch-root.target
@@ -12,5 +12,5 @@ DefaultDependencies=no
 Requires=initrd-switch-root.service
 Before=initrd-switch-root.service
 AllowIsolate=yes
-Wants=initrd-udevadm-cleanup-db.service root-fs.target initrd-fs.target systemd-journald.service
-After=initrd-udevadm-cleanup-db.service root-fs.target initrd-fs.target emergency.service emergency.target
+Wants=initrd-udevadm-cleanup-db.service initrd-root-fs.target initrd-fs.target systemd-journald.service
+After=initrd-udevadm-cleanup-db.service initrd-root-fs.target initrd-fs.target emergency.service emergency.target
diff --git a/units/initrd.target b/units/initrd.target
new file mode 100644
index 0000000000..5622de477a
--- /dev/null
+++ b/units/initrd.target
@@ -0,0 +1,17 @@
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[Unit]
+Description=Initrd Target
+Documentation=man:systemd.special(7)
+OnFailure=emergency.target
+OnFailureIsolate=yes
+ConditionPathExists=/etc/initrd-release
+Requires=basic.target
+Wants=initrd-root-fs.target initrd-fs.target initrd-parse-etc.service
+After=initrd-root-fs.target initrd-fs.target basic.target rescue.service rescue.target
+AllowIsolate=yes