PTY allocation request failed on channel 0


Yesterday, I was trying to login to my machine and I got the following message:

PTY allocation request failed on channel 0

My prompt was stuck and I could not enter commands. This happened because -for some reason- the tty related devices(/dev/ptmx, /dev/pts) were not created or mounted on my machine. In order to get this problem resolved, I created and mounted the missing devices using the following commands:

rm -rf /dev/ptmx
mknod /dev/ptmx c 5 2
chmod 666 /dev/ptmx
umount /dev/pts
rm -rf /dev/pts
mkdir /dev/pts
mount /dev/pts

In order to be able to execute commands you will have to login to your machine(isn’t this supposed to be the original problem :) ).
This will do the trick:

ssh user@host "/bin/bash -i"

My VPS is built on openVZ but I have seen this problem occur also in XEN machines.
Leave me a comment if this works for you!

There are 91 comments in this article:

  1. 5/01/2013Problem ssh'ing into Cross LFS on Raspberry Pi say:

    […] to login as root, a normal error, and one is the tty issue, which is not a normal error. Anyway, this suggests the problem is that the pts devices were not being created as needed. My hunch would be […]

  2. 11/01/2013vasanth say:

    Thanks !! It worked !!

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    Hi, I don’t have a root password set on my VPS, using sudo, instead …

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    As a normal user, of course, I don’t have write permission to anything interesting …
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