A bit more detail
For anyone else who's following this, here's what happened: I was installing Sybase on the RH 8 system. It wants to put itself in /opt (which is right off of the root /)--and that's not a place I have unlimited space.
Well, after putting it on, I get these messages from Linux warning the that / partition is critically low on space; then it starts behaving erratically.
Well, having used rpm to erase the Sybase rpms (the space available on / drops way down--lower than I thought it would), now a bunch of stuff that *was* there and working isn't. E.g., ssh wouldn't load because one of the lib's it wanted was gone (I found that and reloaded it); same thing with X-windows (although figuring out what was missing was a bit more interesting there). Now that I have the GUI back, other things are still missing: the up2date utility for connecting to the RedHat network; the GUI package manager; various other GUI-tools.
I've read the man for rpm till I'm blue in the face. The trouble with man docs for us know-enough-to-be-dangerous types is they don't have examples and they don't have any background or be-careful-about-such-and-such things. So, what I'm wondering sort of falls into three subquestions:
1. What happened? Is this some kind of known behavior that things get overwritten or messed up when space on the root partition goes low? Did using the --erase option on rpm to remove the Sybase rpms pick up and delete the other rpms they depended on?
2. If there was some slick way to recover rather than doing an rpm-by-rpm reload of what's missing, that'd be interesting to know.
3. What's the best way to go about backing up an install of Linux so that if this happens again, I don't end up having to sift through the fiddly bits to get things back? I did download something called partimage--is that the kind of tool to use? It seems to want the partition you're backing up to be unmounted. How do you do that with / or /boot? Do I need to interrupt the boot-up at some early stage or boot from a CD or what?