Managing Packages

Package Management is the subsystem that allows you to install, upgrade or remove software from your system. Linux offers a variety of different package management systems. For the purpose of our intro we will focus on two popular ones apt and yum. Used by Debian and RedHat based/like distributions respectively. Be aware that most actions concerning packages require root access. I will skip the sudo in front of each command and let you figure out what that means.

APT

In Debian based systems the lowest level of package interaction is done via dpkg which can be a tricky command for novice users. To help newbies along their path the advanced package tool apt serves as a frontend to dpkg and makes managing packages easier. We would not be in the Linux world if there would not be some alternatives. Most notably aptitude and for the GUI lovers synaptic. By convention packages meant for Debian have an extension of .deb.

Installing Software

apt by default accesses the Debian repositories, which host multiple ten-thousands of packages. To update the list of available packages you use the apt-get command like this

apt-get update

Searching for a specific package in apt's cache is similarity intuitive

apt-cache search keyword

Installing is done via apt-get install.

TIP

Go on and install something fancy, lets say the latest ruby with development headers that is available in the repository.

A side note here. If you are trying to install software you already have it will be updated if there is a new version available or nothing will be changed.

Keeping up-to-date

Upgrading all installed software to the latest version is fairly simple

apt-get update
apt-get upgrade

At some point in time you will notice that upgrade warns you about some packages that have been kept back.

This is the time to acquaint yourself with dist-upgrade. Roughly speaking dist-upgrade will handle some upgrades that upgrade is to conservative for. For example it will perform upgrades that require the removal or installation of additional packages. The reasoning here is that upgrade should under all circumstances avoid breaking things. Note that while this holds for upgrade it might not hold for the software you are upgrading.

Removing Software

Removing a package might result in cascading removal due to dependencies. That is if package A depends on B and you remove B then A will also be removed. The same holds true for everything depending on B, so removal is a transitive operation. To remove a package simply

apt-get remove package-name

This will remove the package but keep the configuration files.

TIP

Go ahead and figure out how to remove those as well.
Hint: There are at least 3 solutions two of which are not nasty.

dpkg magic

For more advanced interaction lets dive a bit deeper and interact with dpkg directly.

Command	Meaning
dpkg -l	List all packages installed on a system
dpkg -L package	List all files of a package
dpkg -S /path/to/file	Show which package a file belongs to

TIP

Now go and find out which package id belongs to and how dpkg reacts if you try doing the same thing for a random log file.

YUM

Like apt, yum is a frontend to a more basic package management system rpm. rpm is mainly used by RedHat and its derivates but can also be found in non RedHat distributions like SuSe. Alternatives include up2date or if you like visuals yumex.

Installing Software

Use yum search and yum install to get your packages.

Keeping up-to-date

For individual packages use yum update package or just type yum update to update everything that there is to update.

Be aware that the philosophy between Debian and RedHat is very different when it comes to updates. If you want to update everything but exclude the kernel modules you would need to run yum update with an option.

TIP

Go and figure out which option that is.
In addition read up on yum upgrade and what it does for you.

Removing Software

As you would expect yum remove package will remove the given package and related dependencies.

TIP

Figure out what rpm would do.
Also find out what happens to configuration files on package removal with yum and rpm.

rpm magic

As with dpkg lets dive into some backend features. Interacting with rpm directly will save you the overhead of some network request if your actions are only interacting with local packages.

Command	Meaning
rpm -qa	List all packages installed on a system
rpm -ql package	List all files of a package
rpm -qi package	Get information on a package
rpm -qf /path/to/file	Show which package a file belongs to