PTY allocation request failed on channel 0

Recently I tried to ssh into a guest in vmware. I was able to authenticate in the server and I was not able to access the console. I was getting the following error.

$ ssh x.x.x.x
The authenticity of host ‘x.x.x.x (x.x.x.x)’ can’t be established.
RSA key fingerprint is 1c:4d:1b:6g:d5:40:db:5b:46:7f:bb:17:b1:1b:41:80.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added ‘x.x.x.x’ (RSA) to the list of known hosts.
root@x.x.x.x’s password:
PTY allocation request failed on channel 0

On checking the logs from the console, I found the following error.

sshd[2641]: pam_unix(sshd:session): session opened for user root by (uid=0)
sshd[2641]: error: openpty: No such file or directory
sshd[2641]: error: session_pty_req: session 0 alloc failed
sshd[2756]: pam_unix(sshd:session): session opened for user root by (uid=0)
sshd[2756]: error: openpty: No such file or directory
sshd[2756]: error: session_pty_req: session 0 alloc failed

I found that the device file ptmx was missing the server. Now I have to recreate the device file. I googled around for sometime and found the following solution.

$ sbin/MAKEDEV -d /dev ptmx

And it worked. I restarted SSH service and was able to login to the vmware guest. :)

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One Response to “PTY allocation request failed on channel 0”

  1. Thank you! I got this error upgrading my CentOS server to 5.9 and I have sh*t bricks!

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