Wednesday, September 18, 2013

Synergy - software/network based KVM


Synergy is a application that allows you to share one mouse and keyboard with other PCs, similar to a KVM switch.  Typically a person will have a laptop and one or more desktops at his desk - so instead of keeping a separate keyboard/mouse for each, you can just use one to control all of them.


How Synergy works.


I use synergy running on my laptop (Windows 7) to control my desktop (Ubuntu 13.04) - all with the built-in mouse an keyboard on the laptop.

They launch at startup. However on Ubuntu, I created an entry in Startup Applications. However, this will only launch once the user is logged in. To launch Synergy earlier, you can use this recipe (I have not tested it yet).


Synergy requires an X server. That means a server must be running and synergy must be authorized to connect to that server. It's best to have the display manager start synergy. You'll need the necessary (probably root) permission to modify the display manager configuration files. If you don't have that permission you can start synergy after logging in via the .xsession file.
Typically, you need to edit three script files. The first file will start synergy before a user logs in, the second will kill that copy of synergy, and the third will start it again after the user logs in.
The contents of the scripts varies greatly between systems so there's no one definite place where you should insert your edits. However, these scripts often exit before reaching the bottom so put the edits near the top of the script.
The location and names of these files depend on the operating system and display manager you're using. A good guess for the location is /etc/X11. If you use kdm then try looking in /etc/kde3 or/usr/kde/version/share/config. Typical file names are:
    xdm  kdm  gdm
1xdm/Xsetupkdm/Xsetupgdm/Init/Default (*)
2xdm/Xstartupkdm/Xstartupgdm/PostLogin/Default (*)
3xdm/Xsessionkdm/Xsessiongdm/Sessions/Default (*, **)
*) The Default file is used if no other suitable file is found. gdm will try displayname (e.g. :0) and hostname (e.g. somehost), in that order, before and instead of Default.
**) gdm may use gdm/Xsessionxdm/Xsession or dm/Xsession if gdm/Sessions/Default doesn't exist.
For a synergy client, add the following to the first file: /usr/bin/killall synergyc sleep 1 /usr/bin/synergyc [<options>] synergy-server-hostname Of course, the path to synergyc depends on where you installed it so adjust as necessary.
Add to the second file: /usr/bin/killall synergyc sleep 1
And to the third file: /usr/bin/killall synergyc sleep 1 /usr/bin/synergyc [<options>] synergy-server-hostname Note that <options> must not include -f or --no-daemon or the script will never exit and you won't be able to log in.
The changes are the same for the synergy server except replace synergyc with synergys and use the appropriate synergys command line options. Note that the first script is run as root so synergys will look for the configuration file in root's home directory then in /etc. Make sure it exists in one of those places or use the --config config-pathname option to specify its location.
Note that some display managers (xdm and kdm, but not gdm) grab the keyboard and do not release it until the user logs in for security reasons. This prevents a synergy server from sharing the mouse and keyboard until the user logs in. It doesn't prevent a synergy client from synthesizing mouse and keyboard input, though.
If you're configuring synergy to start only after you log in then edit your .xsession file. Add just what you would add to the third file above.
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