Remote reboot over ssh does not restart

Question

I would like to remotely reboot my Ubuntu 12.04 LTS server via ssh. I do sudo reboot and I loose connection and the server connection does not reappear. It does not ping.

When I go the the physical computer with a screen attached I see a black screen and hear that the server is still on. I do a hard power off (press power on button for a few seconds) and the server halts. After I press power on the server boots with no problem.

As far as I remember the remote reboot has previously worked on that server.

I wonder if sudo reboot & will help? I suppose I could also try sudo shutdown -r and see if that does any difference.

I have listed an excerpt of /etc/log/syslog below. The last thing it records is the stopping of the logging.

Oct 24 10:14:49 servername kernel: [1354427.594709] init: cron main process (1060) killed by TERM signal
Oct 24 10:14:49 servername kernel: [1354427.594908] init: irqbalance main process (1080) killed by TERM signal
Oct 24 10:14:49 servername kernel: [1354427.595299] init: tty1 main process (1424) killed by TERM signal
Oct 24 10:14:49 servername kernel: [1354427.637747] init: plymouth-upstart-bridge main process (20873) terminated with status 1
Oct 24 10:14:49 servername kernel: Kernel logging (proc) stopped.
Oct 24 10:14:49 servername rsyslogd: [origin software="rsyslogd" swVersion="5.8.6" x-pid="876" x-info="http://www.rsyslog.com"] exiting on signal 15.
Oct 24 10:25:34 servername kernel: imklog 5.8.6, log source = /proc/kmsg started.
Oct 24 10:25:34 servername rsyslogd: [origin software="rsyslogd" swVersion="5.8.6" x-pid="862" x-info="http://www.rsyslog.com"] start

Solution

Others have had the same problem: Why can't I restart/shutdown?

Colin Watson suggests trying different parameters for reboot= in grub.

Comments

[NorTicUs]

Have you tried both methods you're suggesting ?

[Finn Årup Nielsen]

Not yet. For every reboot I have to walk to another building to get it restarted.

[Finn Årup Nielsen]

I now I tried sudo reboot & and it did not work.

[Finn Årup Nielsen]

I now also tried sudo shutdown -r now non-remotely, - and it did not work. My last messages are Unmounting local filesystems, Will now restart... and [a number] Restarting system which it obviously doesn't do.

[Finn Årup Nielsen]

I have now tried "sudo init 6" in vain.

[Finn Årup Nielsen]

I do not understand "you should update the dmesg and syslog outputs". I think it is after the logs are shut down that the problem begins.

[Finn Årup Nielsen]

And now with GRUB_CMDLINE_LINUX="reboot=b" in /etc/default/grub it seems to work! At least two tests with sudo shutdown -r now got it right back.