virtualbox + ubuntu-16.04LTSでXが起動しないメモ

VirtualBoxでubuntuを走らせ、ubuntuのアップデートでなぜかXが起動しなくなった時のメモ。

なぜかログイン画面がブラックスクリーンのまま。。。

ALT+F1で仮想コンソールを切り替え、ユーザでログイン。下記を実行して改善すれば、lightdmがおかしい。

$ sudo service lightdm restart

自分の場合は、lightdmを再インストールしたら状況が改善した。

$ sudo aptitude reinstall lightdm

(ただし完璧ではなく、たまにブラックスクリーンになったまま)

/var/log/lightdm/lightdm.logを見ると、X Serverがシャットダウンしている。

[+0.13s] DEBUG: Using VT 7
[+0.13s] DEBUG: Seat seat0: Starting local X display on VT 7
[+0.13s] DEBUG: DisplayServer x-0: Logging to /var/log/lightdm/x-0.log
[+0.13s] DEBUG: DisplayServer x-0: Writing X server authority to /var/run/lightd
m/root/:0
[+0.13s] DEBUG: DisplayServer x-0: Launching X Server
[+0.13s] DEBUG: Launching process 894: /usr/bin/X -core :0 -seat seat0 -auth /va
r/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
[+0.13s] DEBUG: DisplayServer x-0: Waiting for ready signal from X server :0
[+0.13s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
[+0.13s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/S
eat0
[+0.14s] DEBUG: Loading users from org.freedesktop.Accounts
[+0.14s] DEBUG: User /org/freedesktop/Accounts/User1000 added
[+0.68s] DEBUG: Process 894 exited with return value 127
[+0.68s] DEBUG: DisplayServer x-0: X server stopped
[+0.68s] DEBUG: Releasing VT 7
[+0.68s] DEBUG: DisplayServer x-0: Removing X server authority /var/run/lightdm/
root/:0
[+0.68s] DEBUG: Seat seat0: Display server stopped
[+0.68s] DEBUG: Seat seat0: Stopping; greeter display server failed to start
[+0.68s] DEBUG: Seat seat0: Stopping
[+0.68s] DEBUG: Seat seat0: Stopping session
[+0.68s] DEBUG: Seat seat0: Session stopped
[+0.68s] DEBUG: Seat seat0: Stopped
[+0.68s] DEBUG: Required seat has stopped
[+0.68s] DEBUG: Stopping display manager
[+0.68s] DEBUG: Display manager stopped
[+0.68s] DEBUG: Stopping daemon
[+0.68s] DEBUG: Seat seat0: Stopping session
[+0.68s] DEBUG: Exiting with return value 1

ubuntu wikiにあるように、こんな時はbug reportを送ってみる。

$ LANG=C ubuntu-bug lightdm

【追記】下記を/etc/rc.localに加えておくことで症状を緩和できる。

service lightdm restart