A method to check whether a package is installed in Debian Linux

If you are managing an Debian or Ubuntu server, you may often use the dpkg or apt-get commands. These two commands are used to install, uninstall, and update packages.

In this article, let's look at how to check if a package is installed on an DEB-based system.

To check if a particular package, such as firefox, is installed, use this command:

  dpkg -s firefox

Sample output:

  Package: firefox
  Status: install ok installed
  Priority: optional
  Section: web
  Installed-Size: 93339
  Maintainer: Ubuntu Mozilla Team <ubuntu-mozillateam@lists.ubuntu.com>
  Architecture: amd64
  Version: 35.0+build3-0ubuntu0.14.04.2
  Replaces: kubuntu-firefox-installer
  Provides: gnome-www-browser, iceweasel, www-browser
  Depends: lsb-release, libasound2 (>= 1.0.16), libatk1.0-0 (>= 1.12.4), libc6 (>= 2.17), libcairo2 (>= 1.2.4), libdbus-1-3 (>= 1.0.2), libdbus-glib-1-2 (>= 0.78), libfontconfig1 (>= 2.9.0), libfreetype6 (>= 2.2.1), libgcc1 (>= 1:4.1.1), libgdk-pixbuf2.0-0 (>= 2.22.0), libglib2.0-0 (>= 2.37.3), libgtk2.0-0 (>= 2.24.0), libpango-1.0-0 (>= 1.22.0), libpangocairo-1.0-0 (>= 1.14.0), libstartup-notification0 (>= 0.8), libstdc++6 (>= 4.6), libx11-6, libxcomposite1 (>= 1:0.3-1), libxdamage1 (>= 1:1.1), libxext6, libxfixes3, libxrender1, libxt6
  Recommends: xul-ext-ubufox, libcanberra0, libdbusmenu-glib4, libdbusmenu-gtk4
  Suggests: ttf-lyx
  Conffiles:
  /etc/firefox/syspref.js 09e457e65435a1a043521f2bd19cd2a1
  /etc/apport/blacklist.d/firefox ee63264f847e671832d42255912ce144
  /etc/apport/native-origins.d/firefox 7c26b75c7c2b715c89cc6d85338252a4
  /etc/apparmor.d/usr.bin.firefox f54f7a43361c7ecfa3874abca2f292cf
  Description: Safe and easy web browser from Mozilla
  Firefox delivers safe, easy web browsing. A familiar user interface,
  enhanced security features including protection from online identity theft,
  and integrated search let you get the most out of the web.
  Xul-Appid: {ec8030f7-c20a-464f-9b0e-13a3a9e97384}

As you can see above, firefox is already installed.

Again, you can use the dpkg-query command. This command will have a better output, of course, you can use wildcards.

  dpkg-query -l firefox

Sample output:

  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 firefox 35.0+build3-0ubuntu0.14 amd64 Safe and easy web browser from Mozilla

To list all the packages installed on your system, type the following command:

  dpkg --get-selections

Sample output:

  abiword install
  abiword-common install
  accountsservice install
  acl install
  adduser install
  alsa-base install
  alsa-utils install
  anacron install
  app-install-data install
  apparmor install
  .
  .
  .
  zeitgeist install
  zeitgeist-core install
  zeitgeist-datahub install
  zenity install
  zenity-common install
  zip install
  zlib1g:amd64 install
  zlib1g:i386 install

The output above can be very long, depending on the packages you have installed on your system.

You can also filter through grep to get more precise packets. For example, I want to view the gcc package installed on the system using the dpkg command:

  dpkg --get-selections | grep gcc

Sample output:

  gcc install
  gcc-4.8 install
  gcc-4.8-base:amd64 install
  gcc-4.8-base:i386 install
  gcc-4.9-base:amd64 install
  gcc-4.9-base:i386 install
  libgcc-4.8-dev:amd64 install
  libgcc1:amd64 install
  libgcc1:i386 install

In addition, you can use the "-L" parameter to locate the files in the package.

dpkg -L gcc-4.8

Sample output:

  /.
  /usr
  /usr/share
  /usr/share/doc
  /usr/share/doc/gcc-4.8-base
  /usr/share/doc/gcc-4.8-base/README.Bugs
  /usr/share/doc/gcc-4.8-base/NEWS.html
  /usr/share/doc/gcc-4.8-base/quadmath
  /usr/share/doc/gcc-4.8-base/quadmath/changelog.gz
  /usr/share/doc/gcc-4.8-base/gcc
  .
  .
  .
  /usr/bin/x86_64-linux-gnu-gcc-4.8
  /usr/bin/x86_64-linux-gnu-gcc-ar-4.8
  /usr/bin/x86_64-linux-gnu-gcov-4.8