How to check whether a software package is installed in Debian Linux

If you are managing a 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.

To check whether a specific 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.

Similarly, 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 packages installed on your system, enter 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 above output may be very long, depending on the packages your system has installed.

You can also use grep to filter and cut more precise packages. For example, I want to use the dpkg command to view the gcc package installed in the system:

  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 find out the location of the files in the package Location.

dpkg -l gcc-4.8

Example 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

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