Is it safe to run X while 'apt-get upgrade'ing?

I think so, or at least: It hasn't crashed so far.

Hell, is it safe to run *gvim* while 'apt-get upgrade'ing? If you ever see this node then the answer is yes, at least this time around.

This... probably isn't a good idea. Replacing libraries is dangerous.

Kids, don't try this at home.

Yes. Or at least I think so.

AFAIK, the particular instances of X, Xlib, or glibc for that matter are not touched. Their code is already in memory. Only future instances are affected.

Ordinarily, I think it would actually not be safe. But since X is a network protocol and not a library, and Xlib is actually a client implementation of that network protocol, newly launched X clients (meaing programs that use X) will not use code specific to the new X server. The thing is, Xlib is server-independent, thus generic code, which should work for any X server. So the new Xlib would not make a difference with the old X server.

One thing that's not safe is leaving your computer halfway through an apt-get upgrade which gets interrupted by an error or for some other reason. I did this, and X started okay, but once it was into GNOME the computer started sending all kinds of random keystrokes to the gnome-terminal I had running. I tried to move my mouse to close it, but the mouse was all fucked up and the pointer jumped around and sent random clicks. It managed to open up mutt and do random things to e-mail messages as I tried ctrl-alt-backspace, which didn't work. And I've got a stupid keyboard which goes catatonic when I press Alt-SysRq. I had no choice but to hit the power button.

Finishing the apt-get upgrade solved everything, but this goes down as the most impressive complete crash of Linux I've seen.

The two things that people commonly (used to) notice when upgrading their systems while in X are sawfish and xfs (or any other font server, like xfs-xtt).

Sawfish users need to run sawfish-client -f restart each time there's a new upstream release. This is often the case with zsh, too (the completion subsystem starts spewing errors).

People who use xfs need to restart X after upgrading because in some strange circumstances, their fonts can get really screwed up, you only see squares instead of characters in some applications.

Apparently it's also sometimes necessary to restart X with some USB mice -- according to avalyn.

So, the general answer is "Yes, if you're not upgrading a production system". :)

Why the downvote? There's nothing but truth here. Get the whole node removed if you think it's useless.