Re: [gdm-list] Testing gdm

To me, this sounds like a job for VirtualBox. If that's not a sandbox, I don't know what is. You can create a snapshot before experimenting, and if it "goes south" you can restore the snapshot and try again in a couple of minutes.

Obviously qemu, VMware, etc are alternative approaches.


Brian Cameron wrote:


I'm tryong to make some modifications to gdm. I've got my shiny new binary, but how do I go about testing it?

gdm seems to be greedy, and running it in Xephyr still results in gdm trying to grab all displays. I just want it to manage the local Xephyr|Xnest|Xgl window, and also want to make sure it's cleanly running only the new binary.

Unfortunately it is not very easy to "test" GDM in any sort of sandbox.
You need to install it and try it out. You can run gdm-restart as root
to restart GDM with the latest installed code to test any changes you
have built and installed.

This can be a pain if you hack GDM in a way that breaks it, in which
case you may need to fix it without X to get it running again. So it is
often useful to have a known working copy you can reinstall if you get
into this situation. Typically I use gdm_debug calls when doing
development and turn on GDM debug so I can see what is going on by
reviewing the syslog. Not the nicest way to debug problems, but it can
be a bit of work to set up a system so you can attach a debugger to the
running GDM processes (e.g. you could use run a debugger after telneting
into the machine from a remote machine). Since GDM is the program which
starts up the user sessions, you often cannot debug GDM issues from user

Though, if your changes are only to the GUI login programs, you can test
these by simply logging out and logging back in after installing the new
GUI code (or logging in via Xephyr, etc.).

You can also set "DOING_GDM_DEVELOPMENT=1" and run the GDM GUI programs
to test them from your normal user session. However running the GUI
programs in this way disables a lot of functionality and may not
be helpful depending on what you are testing. I do not think the new
GDM rewrite GUI programs has this environment variable debugging
feature, though.

Unfortunately messing around with the gdmdynamic command (at least how
the daemon responds to the gdmdynamic command) and automatic login
does not fit into this "GUI development" category.

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