core: add RootImage= setting for using a specific image file as root directory for a service

This is similar to RootDirectory= but mounts the root file system from a
block device or loopback file instead of another directory.

This reuses the image dissector code now used by nspawn and
gpt-auto-discovery.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/core/unit.c b/src/core/unit.c
index 44f1d5e206..90d7eea956 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -862,6 +862,12 @@ int unit_add_exec_dependencies(Unit *u, ExecContext *c) {
                         return r;
         }
 
+        if (c->root_image) {
+                r = unit_require_mounts_for(u, c->root_image);
+                if (r < 0)
+                        return r;
+        }
+
         if (!MANAGER_IS_SYSTEM(u->manager))
                 return 0;