- if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) {
+ /* We first try a pivot_root() so that we can umount the old
+ * root dir. In many cases (i.e. where rootfs is /), that's
+ * not possible however, and hence we simply overmount root */
+ if (pivot_root(new_root, temporary_old_root) >= 0) {
+
+ /* Immediately get rid of the old root. Since we are
+ * running off it we need to do this lazily. */
+ if (umount2(temporary_old_root, MNT_DETACH) < 0) {
+ r = -errno;
+ log_error("Failed to umount old root dir %s: %m", temporary_old_root);
+ goto fail;
+ }
+
+ } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) {