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Package management

Workflow

What is a package manager?

Modern operating systems use package managers to take care of the installation maintenance and removal of software. On Windows this is Windows Installer (formerly Microsoft Installer). On Linux there are two popular package managers:

  • APT (used by Debian, Ubuntu)
  • RPM (RedHat, CentOS, Fedora, SuSe)

Specific commands for each system vary, but at their core they all provide the same functionality:

  • Install and uninstall packages
  • Upgrade packages
  • Install packages from a central repository
  • Search for information on installed packages and files

RPM and yum (RedHat, CentOS, Fedora, Scientific Linux)

In the following examples, we will be using the dstat in our examples. The process however applies to any spftware you may want to install.

Yum provides a wrapper around RPM, which can be used to search, and install packages, from multiple package repositories.

If your Linux distribution uses RPM and yum, you can search search for packages by running:

bash-4.0$ yum search dstat
======================== N/S Matched: dstat =========================
dstat.noarch : Versatile resource statistics tool

Installing packages

You can install a package through yum, by running:

bash-4.0$ yum install dstat

=============================================================================
 Package        Arch            Version              Repository         Size
=============================================================================
Installing:
 dstat          noarch          0.7.0-1.el6          CentOS-6          144 k

Transaction Summary
=============================================================================
Install       1 Package(s)

Total download size: 144 k
Installed size: 660 k
Is this ok [y/N]:

If you have a downloaded RPM file, you can also install the package directly with the rpm command:

bash-4.0$ rpm -i dstat-0.7.0-1.el6.noarch.rpm

Upgrading packages

RPM and yum both make it easy to upgrade existing packages, too. Over time, new packages may be added to the yum repositories that are configured on your system, or you may have a newer RPM for an already installed package.

To upgrade using yum, when a newer package is available, simply ask yum to install it again:

bash-4.0$ yum install dstat

To upgrade a package with an RPM file, run:

bash-4.0$ rpm -Uvh dstat-0.7.1-1.el6.noarch.rpm

Uninstalling packages

To uninstall a package using yum, run:

bash-4.0$ yum remove dstat

Similarly, you can uninstall a package with rpm:

bash-4.0$ rpm -e dstat

Querying the RPM database

Ocassionally you will want to find out specific information regarding installed packages. The -q option to the rpm command comes in handy here. Let's take a look at a few examples:

One common task is to see if you have a package installed. The -qa option by itself will list ALL installed packages. You can also ask it to list specific packages if they are installed:

bash-4.0$ rpm -qa dstat
dstat-0.7.0-1.el6.noarch

Now let's say we want to list all of the files installed by a package. The -ql option is the one to use:

bash-4.0$ rpm -ql dstat
/usr/bin/dstat
/usr/share/doc/dstat-0.7.0
/usr/share/doc/dstat-0.7.0/AUTHORS
/usr/share/doc/dstat-0.7.0/COPYING
/usr/share/doc/dstat-0.7.0/ChangeLog
...

We can also do the reverse of the previous operation. If we have a file, and want to known which package it belongs to:

bash-4.0$ rpm -qf /usr/bin/dstat
dstat-0.7.0-1.el6.noarch

Creating packages

Mention spec files and roughly how RPMs are put together. Then introduce FPM and tell them not to bother with spec files yet.

dpkg and APT (Debian, Ubuntu)

In the following examples, we will be using the dstat in our examples. The process however applies to any spftware you may want to install.

apt provides a wrapper around dpkg, which can be used to search, and install packages, from multiple package repositories.

If your Linux distribution uses dpkg and apt, you can search search for packages by running:

bash-4.0$ apt-cache search dstat
dstat - versatile resource statistics tool

Installing packages

You can install a package through apt, by running:

bash-4.0$ apt-get install dstat

The following NEW packages will be installed:
  dstat
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/79.3 kB of archives.
After this operation, 351 kB of additional disk space will be used.
Selecting previously unselected package dstat.
(Reading database ... 124189 files and directories currently installed.)
Unpacking dstat (from .../archives/dstat_0.7.2-3_all.deb) ...
Processing triggers for man-db ...
Setting up dstat (0.7.2-3) ...

If you have a downloaded DEB file, you can also install the package directly with the dpkg command:

bash-4.0$ dpkg -i dstat_0.7.2-3_all.deb

Upgrading packages

dpkg and APT both make it easy to upgrade existing packages, too. Over time, new packages may be added to the apt repositories that are configured on your system, or you may have a newer deb for an already installed package.

To upgrade using apt, when a newer package is available, simply ask apt to install it again:

bash-4.0$ apt-get install dstat

To upgrade a package with an deb file, run:

bash-4.0$ dpkg -i dstat_0.7.2-3_all.deb

Uninstalling packages

To uninstall a package using apt, run:

bash-4.0$ apt-get remove dstat

Similarly, you can uninstall a package with dpkg:

bash-4.0$ dpkg -r dstat

With APT and dpkg, removing a package still leaves behind any configuration files, in cast you wish to reinstall the package again later. To full delete packages and their configuration files, you need to purge:

bash-4.0$ apt-get purge dstat

or:

bash-4.0$ dpkg -P dstat

Querying the dpkg database

Ocassionally you will want to find out specific information regarding installed packages. The dpkg-query command has many options to help with this. Let's take a look at a few examples:

One common task is to see if you have a package installed. The -l option by itself will list ALL installed packages. You can also ask it to list specific packages if they are installed:

bash-4.0$ dpkg-query -l dstat
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version      Architecture Description
+++-==============-============-============-==================================
ii  dstat          0.7.2-3      all          versatile resource statistics tool

Now let's say we want to list all of the files installed by a package. The -L option is the one to use:

bash-4.0$ dpkg-query -L dstat
/.
/usr
/usr/bin
/usr/bin/dstat
/usr/share
...

We can also do the reverse of the previous operation. If we have a file, and want to known which package it belongs to:

bash-4.0$ dpkg-query -S /usr/bin/dstat
dstat: /usr/bin/dstat

Creating packages

Mention spec files and roughly how debs are put together. Then introduce FPM and tell them not to bother with spec files yet.