t.Skipf("skipping: could not start process with CLONE_NEWNS and CLONE_NEWUSER: %v", err)
		}
		t.Fatalf("Cmd failed with err %v, output: %s", err, out)
	}
}

func prepareCgroupFD(t *testing.T) (int, string) {
	t.Helper()

	const O_PATH = 0x200000 // Same for all architectures, but for some reason not defined in syscall for 386||amd64.

	// Requires cgroup v2.