my vanishing root partition

Okay, so riddle me this: Why does space on my root partition keep disappearing? I first noticed something weird with k3b. I tried to change the theme to something I liked better, and was asked to make a tmp folder: /tmp/kde-<USERNAME> So I did this, but every time I reboot, the same problem occurs, and I have to go through these steps manually, again and again. Then I got the bright idea to create the partition myself by command-line, anticipating the problem: sudo mkdir /tmp/kde-<USERNAME> And the first time I did this, it worked; but after reinstalling my system (some months ago), I have the same problem again, and nothing works to fix it. This, however, is just the tip of the iceberg. Something keeps eating space on my root partition. I used to have over 1 gb to spare, but this kept shrinking, even when I wasn't installing anything new. Now kdf tells me that I am down to 262 mb of space left on my root partition (on a fresh reboot); this, I predict - based on past experience - will gradually shrink down to 0 over a couple days. (This, by the way, is why I want to resize my root partition with gparted, slacko, Parted Magic, whatever, so that I have more room to wiggle. I used to allot at least 25-30 gb for my root partition; but then I thought, hey, I've got my system pretty well set up, and won't be downloading much of anything new, and I'm very hygienic about cleaning out extraneous unnecessary crap. The newer distros, though, use up more and more space on the root partition, just because they can; due to the fact that hard drives are getting bigger and cheaper - even though not all of us can afford to go out and buy a new one right now.) And there's more. For example: I tried burning the gparted live iso image to a CD, and k3b tells me "SUCCESS!"; but when I load the disc, it tells me it's empty. Also, when I have been downloading stuff to other drives (not root), I can watch kdf show my root partition shrinking at a rate of 1 mb every few minutes; or when I copy files from one hard drive to another, the same thing happens. There are lots of other little things like this, which seem to point to the same problem, but you get the general idea. I would like to blame this on systemd or something like that (and it's true that systemd seems to interfere with shutdowns and reboots); but I am trying to keep an open mind, as it could be another problem. All in all, something is eating space on my root partition, but I can't track down the culprit. My antivirus is up-to-date; my firewall blocks EVERYTHING outgoing and only allows secure, encrypted connections on a few ports. I keep watching for some kind of activity that might show me what's going on, but so far it's a mystery. I'm intending to resize my root partition back to 30 gb. (Everything's already backed up and ready to go.) But if this is a different, bigger problem, I would like to sort that out first. Anybody have a clue what's happening? I will be eternally grateful, or at least I'll be grateful for a pretty long time. Bill