- apt-get dist-upgrade [--simulate]: upgrade the system
- apt-get install pkg_name: install the package called pkg_name
- apt-file search <filename> uses the apt system (Debian/Ubuntu) to find which package (installed or not) provides file <filename>
- apt-file search pattern finds packages with names or containing files that match pattern.
- Add repository: sudo add-apt-repository ppa:repository-name
- Remove repository: sudo rm /etc/apt/sources.list.d/repository-name
- If you accidently install a package (using dpkg -i) that causes conflicts, you can revert to the old version by manually downloading it from http://packages.ubuntu.com/ (or your distribution's packages server), and installing it with dpkg -i. Of course, if it has no dependencies, then you can simply remove it and reinstall the version from the appropriate repository, but if it has dependencies, apt-get won't let you remove it. There are supposed to be other ways to revert to old versions, but I found this the only one to work.