OpenBSD creating additional ptys
I like a lot of windows. A lot of them. Today I bumped into a default limit on OpenBSD 4.8 and tmux(1) started returning “No such file or directory” when I attempted to create a new window. This turned out to be a simple thing to solve, though.
By default, OpenBSD only creates 63 pseudo-terminals in /dev. Luckily, creating additional ptys is as simple as:
# cd /dev
# ls -1 | grep -c pty
63
# sh MAKEDEV pty1
# sh MAKEDEV pty2
# sh MAKEDEV pty3
# ls -1 | grep -c pty
248
You can keep going up to pty15 for a total of 992 ptys.
tech stuff. 
Thank you for posting this – I came across this problem on an AuthPF system. Worked like a charm to add more pseudo terminals.
Leslie Richardson
2012-03-27 at 10:55