Red Hat :: "Lost" User Mysql While Updating System

I ran up2date yesterday and it installed a few new MySQL packages as well as a new kernel.

It got through everything up until it went to install the smp version of the kernel, and up2date spit an error at me and quit.

The problem was that my system keeps old kernels and /boot was full, so it couldn't add the new files there. No problem--I manually removed (via rpm -e) six or seven of the old kernel packages (there might have been a dozen or so), ran up2date again, and it successfully installed the new kernel. Great. So I rebooted the system.

And when it came back up... MySQL didn't start.

I tried to manually start it just to see, and was greeted with "chown: 'mysql:mysql': invalid user" Yikes! Sure enough, a look at /etc/passwd showed NO user "mysql." I quickly tried "useradd mysql" but it wouldn't go for that because there was a GROUP mysql.

I checked to make sure that there was no user with an id matching the group id of mysql and then manually added mysql back to /etc/passwd and /etc/shadow.

After doing that I was able to start the MySQL daemon and it now properly starts up and runs fine after rebooting.

So basically, it's fixed, but I still don't exactly understand what the heck happened. Updating to a new MySQL rpm and having up2date fail while installing a new kernel somehow deletes my "mysql" user from the system? I shouldn't have to be manually modifying /etc/passwd and /etc/shadow because of an up2date error, I wouldn't think.

Edit-- This is a RHEL 4 system now running 2.6.9-89.0.20.ELsmp on a Dell PowerEdge 1750..