[OpenVZ]Solution for "Unable to open pty ..."

OpenVZ Forumに、ズバリな解決方法がpostされていた。

I have same trouble and this looks very strange. As solution (inside problematic VZ) simply add the line 'ptmx' in file /etc/udev/makedev.d/50-udev.nodes (for CentOS 5) and is works fine after reboot.

つまりVPSがCentOS5なら、

# echo 'ptmx' >> /var/lib/vz/root/[VEID]/etc/udev/makedev.d/50-udev.nodes
# vzctl reboot [VEID]

で解決。
なるほどねぇ。