I’ve been playing with Xen on a Debian host machine. I created a couple of guest machines using xen-create-image (set to use debootstrap to automatically install + configure a basic Debian install on the guest), and was unable to SSH to the guests - I got:
[davidp@masterplan ~]$ ssh 10.1.1.20 -l root
root@10.1.1.20’s password:
PTY allocation request failed on channel 0
stdin: is not a tty
I struggled with this for a while, for some reason accessing the guest’s console with xm console didn’t seem to work either.
However, I now managed to get console access to one of them using xm console domain, and found that /dev/pts wasn’t mounted - it wasn’t listed in the fstab file that had been created.
I added the following to /etc/fstab :
none /dev/pts devpts defaults 0 0
Now I can SSH to the guests. 
To expand on that a little, I found that creating /dev/pts then mounting it (as described in the post) worked, but it was gone again after the guest was rebooted, as /dev/pts no longer existed again.
Once it was mounted again, I did an apt-get install udev, and all was well afterwards.
*LOL* I had the same problem last week… After upgrading Xen+Guests to lenny i had this problems.
1. “xm console” was not avaliable
Guest console stopped output after mounting partitions
Solution:
Add extra = ‘xencons=tty’ to guest config
2. no ssh-login
see error in the article
Solution:
Install udev package on the guest os.
Regards.
PS: Pls, post one week earlier next time
Thanks for the tipp. It works for CentOS as well.
Just mount /dev/pts after adding the line
to /etf/fstab.
Great.
bsn