After I reboot my xen-powered [Linux VPS](http://www.linode.com/?r=cd5198f9daf6a668424aea5534f74baf343f4759), I can't ssh into it any more, it keeps saying:

PTY allocation request failed on channel 0

This problem can be fixed by adding one line to /etc/fstab:

none /dev/pts devpts defaults 0 0

and run "mount -a" after it is added.

What confuses me is why it breaks just after I reboot it, but it works fine before, actually I didn't change anything since last time I rebooted it, maybe it's [Linode](http://www.linode.com/?r=cd5198f9daf6a668424aea5534f74baf343f4759) who changed some settings?