+ if (getpid() == 1) {
+ /* If we are PID 1 we can just check our own
+ * environment variable */
+
+ e = getenv("container");
+ if (isempty(e)) {
+ r = 0;
+ goto finish;
+ }
+ } else {
+
+ /* Otherwise, PID 1 dropped this information into a
+ * file in /run. This is better than accessing
+ * /proc/1/environ, since we don't need CAP_SYS_PTRACE
+ * for that. */
+
+ r = read_one_line_file("/run/systemd/container", &m);
+ if (r == -ENOENT) {
+
+ /* Fallback for cases where PID 1 was not
+ * systemd (for example, cases where
+ * init=/bin/sh is used. */
+
+ r = getenv_for_pid(1, "container", &m);
+ if (r <= 0) {
+
+ /* If that didn't work, give up,
+ * assume no container manager.
+ *
+ * Note: This means we still cannot
+ * detect containers if init=/bin/sh
+ * is passed but privileges dropped,
+ * as /proc/1/environ is only readable
+ * with privileges. */
+
+ r = 0;
+ goto finish;
+ }
+ }
+ if (r < 0)
+ return r;
+
+ e = m;
+ }