Lerna

That creature, bred in the swamp of Lerna, used to go forth into the plain and ravage both the cattle and the country. Now the hydra had a huge body, with nine heads, eight mortal, but the middle one immortal.

Bibliotheca

What

Lerna is a tool to make itinerant computing easier. It watches for changes to the connected displays and configures X.org to use what it deems to be the best display.

If

• you use a Linux laptop,
• you use an external monitor, and
• you want to use a single display at a time

then Lerna might be useful to you. If you want to use multiple displays, it won't be immediately useful, but it might still be a good starting point.

How

$ lerna

You'll see output something like this:

[2014-08-02T04:10:06.592689Z #13059] Switching to DP2
[2014-08-02T04:11:17.008609Z #13059] DP2 => disconnected
[2014-08-02T04:11:17.008764Z #13059] Switching to LVDS1
[2014-08-02T04:11:21.521592Z #13059] DP2 => connected
[2014-08-02T04:11:21.521679Z #13059] Switching to DP2

To see more options, use:

$ lerna --help

An example Upstart script for Ubuntu (pre-15.04) is provided in the support directory. This assumes that lerna is in the path; if it's not, you'll need to adjust this.

You can then use

$ start lerna

to start the job immediately; it should start and stop automatically with your desktop session thereafter.

Wanted

• Example job for systemd
• More strategies
• Ability to read from a configuration file (and reload on change)