When I want to connect to my server like this
ssh -a username@my-server.de -p 22
it gives me two error messages:
PTY alloca
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.
just found out, what was the problem in my case (provider strato): I had the same problem with output "shell request failed on channel 0" in the end.
I have to use the master password with the web-domain name as login. (In German www.wunschname.de, where wunschname is your web-address.)
A ssh login with sftp-user names and the corresponding passwords is without success. (Although scp and sftp works with these sftp users!)