In addition to [snapshots of the filesystem](butter-bei-die-fische.html), I like to keep a copy of the packages I installed. Fortunately, the package managers of Debian and Archlinux do that by default. After some time, however, this cache occupies a lot of hard disk space. I've thus [moved](move-the-cache.html) the cache to an external drive for my Mini, but I also don't want to waste precious SSD space on my Desktop just for static packages kept for being on the safe side. How to do that on Arch? Very simple: Add CacheDir = /your/favorite/path to the [options] section of your /etc/pacman.conf. If a package misbehaves, you can then easily downgrade by issuing a 'pacman -U '. Up to now, I've needed that only once, but I was happy to have this simple solution at hand.