machine-id-setup: add a machine_id_commit call to commit on disk a transient machine-id

If /etc was read only at boot time with an empty /etc/machine-id, the latter
will be mounted as a tmpfs and get reset at each boot. If the system becomes rw
later, this functionality enables to commit in a race-free manner the
transient machine-id to disk.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/shared/util.c b/src/shared/util.c
index 21651708d5..4fcbab97be 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -3052,6 +3052,15 @@ _pure_ static int is_temporary_fs(struct statfs *s) {
                F_TYPE_EQUAL(s->f_type, RAMFS_MAGIC);
 }
 
+int is_fd_on_temporary_fs(int fd) {
+        struct statfs s;
+
+        if (fstatfs(fd, &s) < 0)
+                return -errno;
+
+        return is_temporary_fs(&s);
+}
+
 int rm_rf_children(int fd, bool only_dirs, bool honour_sticky, struct stat *root_dev) {
         struct statfs s;