Desktop location

Sometimes upgrades cause the location of the desktop to be lost. I've only seen this happen under Gnome, but it could also affect KDE.

To reset the location edit ~/.config/user-dirs.dirs.
Here's a good one:

XDG_DESKTOP_DIR="$HOME/Desktop"
XDG_DOWNLOAD_DIR="$HOME/Download"
XDG_TEMPLATES_DIR="$HOME/Templates"
XDG_PUBLICSHARE_DIR="$HOME/Public"
XDG_DOCUMENTS_DIR="$HOME/Documents"
XDG_MUSIC_DIR="$HOME/Music"
XDG_PICTURES_DIR="$HOME/Pictures"
XDG_VIDEOS_DIR="$HOME/Videos"

apt-get public key

From time to time 'apt-get update' will say something like 'There is no public key available for the following key ID 1234'.

To fix do:
gpg --keyserver wwwkeys.eu.pgp.net --recv-keys 1234
gpg --armor --export 1234 | apt-key add -