Create initrd-root-device.target synchronization point (#3239)

Add a synchronization point so that custom initramfs units can run
after the root device becomes available, before it is fsck'd and
mounted.

This is useful for custom initramfs units that may modify the
root disk partition table, where the root device is not known in
advance (it's dynamically selected by the generators).

2 files changed, 19 insertions, 1 deletions

diff --git a/src/shared/generator.c b/src/shared/generator.c
index cd3c35cd55..70afc6a285 100644
--- a/src/shared/generator.c
+++ b/src/shared/generator.c
@@ -65,7 +65,7 @@ static int write_fsck_sysroot_service(const char *dir, const char *what) {
                 "Description=File System Check on %2$s\n"
                 "DefaultDependencies=no\n"
                 "BindsTo=%3$s\n"
-                "After=%3$s local-fs-pre.target\n"
+                "After=initrd-root-device.target local-fs-pre.target\n"
                 "Before=shutdown.target\n"
                 "\n"
                 "[Service]\n"
@@ -191,3 +191,17 @@ int generator_write_timeouts(
                                     "[Unit]\nJobTimeoutSec=%s",
                                     program_invocation_short_name, timeout);
 }
+
+int generator_write_initrd_root_device_deps(const char *dir, const char *what) {
+        _cleanup_free_ char *unit = NULL;
+        int r;
+
+        r = unit_name_from_path(what, ".device", &unit);
+        if (r < 0)
+                return log_error_errno(r, "Failed to make unit name from path: %m");
+
+        return write_drop_in_format(dir, SPECIAL_INITRD_ROOT_DEVICE_TARGET, 50, "root-device",
+                                    "# Automatically generated by %s\n\n"
+                                    "[Unit]\nRequires=%s\nAfter=%s",
+                                    program_invocation_short_name, unit, unit);
+}
diff --git a/src/shared/generator.h b/src/shared/generator.h
index a734e13970..a6017c1b76 100644
--- a/src/shared/generator.h
+++ b/src/shared/generator.h
@@ -34,3 +34,7 @@ int generator_write_timeouts(
         const char *where,
         const char *opts,
         char **filtered);
+
+int generator_write_initrd_root_device_deps(
+        const char *dir,
+        const char *what);