CTID=100
vzctl exec $CTID “mount -t devpts devpts /dev/pts”
vzctl enter $CTID

it works on Debian containers.

vzctl exec 101 /sbin/MAKEDEV tty
vzctl exec 101 /sbin/MAKEDEV pty
vzctl exec 101 mknod –mode=666 /dev/ptmx c 5 2
vzctl enter 101

On RH OS.