How to fix request failed on channel 0

Question

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         


        

Answer 1

I solved a similar problem with one of our users who was used only for ssh port forwarding so he don't need to have access to PTY and it was prohibited in .ssh/authorized_keys file:

no-pty ssh-rsa AAA...nUB9 someuser

So when you tried to log in to this user, only message

PTY allocation request failed on channel 0

was returned. So check your user's authorized_keys file.

Answer 2

This was happening when I was trying to use sudo on ssh -t git@github.com after adding my local user's public key to github

Just a head's up to the google happy people like me

Answer 3

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

Answer 4

Just add these lines to your /etc/mtab and /etc/fstab, and reboot the system.

none    /dev/pts    devpts    defaults    0    0

Answer 5

I occasionally see this when spinning up a VM. Our automation system starts applying updates, so depending on timing can hit an update to critical packages.

Upshot - this might happen if ssh or other related packages are being updated on the destination machine.

Answer 6

rebooting the instance from AWS console worked for me. There was a service that was leaking file connections that lsof helped find.