5 Simple APT Tricks for Debian and Ubuntu

Here are five simple tricks for APT, the Advanced Packaging Tool used on Debian and Debian-based distributions like Ubuntu.

View all the packages installed on a system
The easiest way to do it is:

dpkg --get-selections

It does not require to be root, and will display all the packages installed via APT. For example, the first lines may look something like:

$ dpkg --get-selections | head
acetoneiso2                                     install
acidrip                                         install
acpi-support-base                               install
acpid                                           install
adduser                                         install
akregator                                       install
alien                                           install
alsa-base                                       install
alsa-oss                                        install
alsa-utils                                      install

You can also put the entire list in a text file by redirecting the output, like this:

dpkg --get-selections > installed_packages.txt

Then read this file with a text editor or using less installed_packages.txt.

List files which get installed by a package
-L is a handy parameter to dpkg which will show you what files a package will install.

dpkg -L package_name

For example:

dpkg -L amarok

Will show all the files which are going to be installed by package amarok. You don't have to be root to run it.

Upgrade your system using a one-liner
Type as root:

apt-get update && apt-get dist-upgrade

This command will update your list of packages, and if its return status is successful, it will proceed to the next command, apt-get dist-upgrade, which will upgrade all of your packages and will install new dependencies if needed. Use dist-upgrade when you want all of your packages to be installed, and no package left as being kept back.

Install the dependencies of an application
Sometimes you need to compile from source a newer version of an application which is already included in the repositories. For example, to install the development libraries for BasKet, you would run as root:

apt-get build-dep basket

And then you can proceed to compile your application. Note that sometimes newer versions of applications may depend on newer libraries or other packages than you do not have in the repositories, so this won't always work.

Remove unused package files
When you install software using APT, the DEB packages are kept inside the /var/cache/apt/archives directory. In time, the size of it could get very large. To see what is the size of that directory, you can use:

$ du -h /var/cache/apt/archives/
4.0K    /var/cache/apt/archives/partial
956M    /var/cache/apt/archives/

In order to clean up all these packages you can use, as root:

apt-get clean

This command will remove all the packages except files which are locked. There is another command, apt-get autoclean, which will remove all the packages which are no longer available in the repository (older versions of packages which can't be downloaded any more).