How to fix request failed on channel 0

PTY allocation request failed on channel 0

There is a limit of 256 pseudo terminals on a system. Maybe you have an application that is leaking pseudo terminals. Use

lsof /dev/pts/*

to see what processes have open pseudo-terminals

shell request failed on channel 0

I was getting this error (without PTY allocation error). It turns out that one of my applications (QtCreator 3.0.?) was leaking Zombie processes. Other users were able to log in so I might have been hitting my per user process quota (if there is such a thing). I've updated to QtCreator 3.3. So far so good.

unmount and mount /dev/pts worked for me

umount /dev/pts

mount devpts /dev/pts -t devpts

Reference: http://www.iitk.ac.in/LDP/LDP/lfs/5.0/html/chapter06/proc.html