而且，我再ubuntu bug反馈哪里看到这个，说是网络卸载的问题
Your system isn’t too happy because of bug 1452644. This is fixed in vivid-proposed, but this hasn’t made it into -updates yet. This causes network mounts etc. to fail. That might be related to the shutdown problems. To get this out of the way, could you install the -proposed setserial and re-test?
Secondly, I suppose you actually used “reboot” (or the corresponding indicator action), and not “halt”?
Can you please run “sudo systemctl start debug-shell”, then shut down/reboot, and when it hangs do Ctrl+Alt+F9 look at “systemctl list-jobs” (hanging jobs), or “dmesg” if you see any hanging jobs/errors there? Do you get some meaningful errors at the end of “journalctl”? You could try booting without “quiet splash” and with “debug” instead to increase verbosity what’s going on, shut down, and capture what’s being logged?
Changed in systemd (Ubuntu):
status : New → Incomplete