今天测试了OpenBSD 4.7的snapshot，发现tmux可以使用了。
DESCRIPTION
tmux is a terminal multiplexer: it enables a number of terminals to be
created, accessed, and controlled from a single screen. tmux may be de-
tached from a screen and continue running in the background, then later
reattached.
When tmux is started it creates a new session with a single window and
displays it on screen. A status line at the bottom of the screen shows
information on the current session and is used to enter interactive com-
mands.