13 March 2012

107. Fun with gnu screen -- setting up a screenrc

This is going to be a short post.

The problem:
If I have three nodes on a cluster, each with htop installed, how do I set up gnu screen so that it automatically signs in to each node and starts a copy of htop on each node, and display the output in a split window? Basically, how to you open screen instances and inject commands in them?

...like so. Guess which computer is running a full gnome-shell environment...

The solution:
create a file called multitop.screenrc:

screen ssh
stuff htop\015
title node01
screen ssh
title node02
stuff htop\015
screen ssh
title node03
stuff htop\015
stuff string injects string into the active window. \015 basically injects <enter>.

start screen using
screen -c multitop.screenrc 
and as usual,don't exit using exit or q, but use C+a - d to leave it running.

To make things a bit prettier and to enable users to reconnect to a running session, edit /etc/screenrc:

multiuser on
acladd me
defscrollback 5432
termcapinfo xterm|xterms|xs|rxvt ti@:te@
caption     always        "%{+b rk}%H%{gk} |%c %{yk}%d.%m.%Y | %72=Load: %l %{wk}"
hardstatus alwayslastline "%?%{yk}%-Lw%?%{wb}%n*%f %t%?(%u)%?%?%{yk}%+Lw%"
sudo chmod +s /usr/bin/screen
sudo chmod 755 /var/run/screen

If you start a session using e.g.
screen -S mytest
as user me

then other users can connect using
screen -x me/mytest

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