Debian – How to Check if a Specific Package is Installed

aptdebiandpkgpackage-management

I'm working with a Raspberry Pi B+ and Raspbian 5/5/2015 and some guides that are a few years old. I've got an external NTFS HDD hooked up to the Pi. Due to the articles age(s), common practices have changed, and it turns out that certain packages and features and functions are now built-in and/or automatic.

For example, I found out that Raspbian will handle the automounting of an NTFS drive/volume if you just install ntfs-3g. All instructions and guidance I could find (IRC, raspberry pi forum, and a Linux dude I know) all went extremely technical doing who-knows-what to my system to try to assist me, when in reality we were all tripping over automatic features that no one knew about or thought to check. I've since installed Raspbian fresh to a new SD card and so far just turned on SSH, updated apt-get, and installed ntfs-3g.

This is the article I am using right now: http://www.howtogeek.com/139433/how-to-turn-a-raspberry-pi-into-a-low-power-network-storage-device/?PageSpeed=noscript

My next step is to get Samba up and running. Yes, I know Linux people hate Windows, but I'm a Windows guy, so until I can know enough about Linux for a Linux system to be my fallback, Windows machines are my fallbacks. Eventually this Raspberry Pi will get a multi-TB drive, though for right now it's just a few GB; which is why it needs to be NTFS.

I would like to check if Samba is installed, since the next step in my instructions tell me how to install and configure it. I've tried a few commands and I'm not sure what to do with the results or how to use them. I searched here and the technical details are above my capabilities and I don't think they address my seemingly simple need to find out if a package is installed or not.

I tried:

apt-cache dump

this gave me way too much data. It scrolled down for a few minutes. I got this from The Raspberry Pi Handbook 3rd Edition (Link – Amazon)

I tried

apt-cache showpkg samba
Package: samba
Versions:
2:3.6.6-6+deb7u5 (/var/lib/apt/lists/mirrordirector.raspbian.org_raspbian_dists_                                  wheezy_main_binary-armhf_Packages)
 Description Language:
                 File: /var/lib/apt/lists/mirrordirector.raspbian.org_raspbian_d                                  ists_wheezy_main_binary-armhf_Packages
                  MD5: 0122ac62ef5f4ae21eb2e195eb45ad1d


Reverse Depends:
  winbind,samba 2.2.3-2
  task-file-server,samba
  swat,samba 2:3.6.6-6+deb7u5
  smbclient,samba 2.999+3.0.alpha21-4
  samba4-common-bin,samba 2:3.3.0~rc2-5
  samba4,samba 2:3.3.0~rc2-5
  samba-dbg,samba 2:3.6.6-6+deb7u5
  samba-common-bin,samba 3.0.20b-1
  samba-common,samba 3.0.20b-1
  qtsmbstatus-server,samba
  qemu-system,samba
  nautilus-share,samba 3.0.27a
  libwbclient0,samba 2:3.4.1
  libpam-winbind,samba 2.2.3-2
  libpam-smbpass,samba
  libnss-winbind,samba 2.2.3-2
  gadmin-samba,samba
  education-main-server,samba
  dpsyco-samba,samba
Dependencies:
2:3.6.6-6+deb7u5 - samba-common (5 2:3.6.6-6+deb7u5) libwbclient0 (5 2:3.6.6-6+d                                  eb7u5) libacl1 (2 2.2.51-8) libattr1 (2 1:2.4.46-8) libc6 (2 2.13-28) libcap2 (2                                   2.10) libcomerr2 (2 1.01) libcups2 (2 1.4.0) libgcc1 (2 1:4.4.0) libgssapi-krb5                                  -2 (2 1.10+dfsg~) libk5crypto3 (2 1.6.dfsg.2) libkrb5-3 (2 1.10+dfsg~) libldap-2                                  .4-2 (2 2.4.7) libpam0g (2 0.99.7.1) libpopt0 (2 1.14) libtalloc2 (2 2.0.4~git20                                  101213) libtdb1 (2 1.2.7+git20101214) zlib1g (2 1:1.1.4) debconf (18 0.5) debcon                                  f-2.0 (0 (null)) libpam-runtime (2 1.0.1-11) libpam-modules (0 (null)) lsb-base                                   (2 3.2-13) procps (0 (null)) update-inetd (0 (null)) adduser (0 (null)) dpkg (2                                   1.15.7.2) openbsd-inetd (16 (null)) inet-superserver (0 (null)) smbldap-tools (0                                   (null)) ldb-tools (0 (null)) ctdb (0 (null)) logrotate (0 (null)) tdb-tools (0                                   (null)) samba4 (3 4.0.0~alpha6-2) samba-common (1 2.0.5a-2)
Provides:
2:3.6.6-6+deb7u5 -
Reverse Provides:
pi@raspberrypi ~ $ apt-cache showpkg ntfs-3g
Package: ntfs-3g
Versions:
1:2012.1.15AR.5-2.1+deb7u2 (/var/lib/apt/lists/mirrordirector.raspbian.org_raspbian_dists_wheezy_main_binary-armhf_Packages) (/var/lib/dpkg/status)
 Description Language:
                 File: /var/lib/apt/lists/mirrordirector.raspbian.org_raspbian_dists_wheezy_main_binary-armhf_Packages
                  MD5: b2df024e8627b5d253b85f35263376ef


Reverse Depends:
  udisks,ntfs-3g
  ntfsprogs,ntfs-3g
  ntfs-config,ntfs-3g
  ntfs-3g-dev,ntfs-3g 1:2012.1.15AR.5-2.1+deb7u2
  ntfs-3g-dbg,ntfs-3g 1:2012.1.15AR.5-2.1+deb7u2
  kvpm,ntfs-3g
  fsarchiver,ntfs-3g
Dependencies:
1:2012.1.15AR.5-2.1+deb7u2 - debconf (18 0.5) debconf-2.0 (0 (null)) libc6 (2 2.13-28) libfuse2 (2 2.8.1) libgcc1 (2 1:4.4.0) libgcrypt11 (2 1.4.5) libgnutls26 (2 2.12.17-0) multiarch-support (0 (null)) fuse (0 (null)) libntfs-3g75 (0 (null)) ntfsprogs (3 1:2011.10.9AR.1-3~) libntfs-3g75 (0 (null)) ntfsprogs (0 (null))
Provides:
1:2012.1.15AR.5-2.1+deb7u2 -
Reverse Provides:
pi@raspberrypi ~ $ apt-cache showpkg ntfsprogs
Package: ntfsprogs
Versions:
1:2012.1.15AR.5-2.1+deb7u2 (/var/lib/apt/lists/mirrordirector.raspbian.org_raspbian_dists_wheezy_main_binary-armhf_Packages)
 Description Language:
                 File: /var/lib/apt/lists/mirrordirector.raspbian.org_raspbian_dists_wheezy_main_binary-armhf_Packages
                  MD5: 95f41af9cf1d0b5b66afb7d2a9e7c75d


Reverse Depends:
  partitionmanager,ntfsprogs
  ntfs-3g,ntfsprogs
  ntfs-3g,ntfsprogs 1:2011.10.9AR.1-3~
  gparted,ntfsprogs
  fsarchiver,ntfsprogs
  fai-setup-storage,ntfsprogs
Dependencies:
1:2012.1.15AR.5-2.1+deb7u2 - ntfs-3g (0 (null))
Provides:
1:2012.1.15AR.5-2.1+deb7u2 -
Reverse Provides:

but I'm not sure what to make of the results. I can't tell if it's going to apt-get the servers and getting information, or pulling it from my system.

I tried :

dpkg --get-selections

which I got from here:
http://www.howtogeek.com/howto/linux/show-the-list-of-installed-packages-on-ubuntu-or-debian/?PageSpeed=noscript
but I think I'm running into the same problem. It seems the syntax has changed since 2007. The man page / help file seems to lead me to believe that the command should work

Usage: dpkg [<option> ...] <command>

--get-selections [<pattern> ...] Get list of selections to stdout.

but I get an error:

dpkg –get-selections samba
dpkg: error: need an action option

I found a few wuestions here that are related, but don't give me what I am looking for. I am interested in just knowing what's installed, but I guess that's a topic for another question.

Best Answer

apt-cache showpkg shows detailed information about potentially installable packages. It does indicate whether the package is installed, kind of, but not in a very readable way:

Versions:
2:3.6.6-6+deb7u5 (/var/lib/apt/lists/mirrordirector.raspbian.org_raspbian_dists_wheezy_main_binary-armhf_Packages)

If the package was installed, you'd see (/var/lib/dpkg/status) at the end of the line. However, this isn't fully reliable, because you'd also see this indication if the package was known to your system but not fully installed, e.g. if it was in the “package uninstalled but configuration files left over” state.

A more useful apt-cache subcommand is apt-cache policy. It clearly shows the installed version (if any) and the available version(s). For example, here's output from a machine which has samba installed but not samba-dev:

samba:
  Installed: 2:4.1.17+dfsg-2
  Candidate: 2:4.1.17+dfsg-2
  Version table:
 *** 2:4.1.17+dfsg-2 0
        500 http://ftp.fr.debian.org/debian/ jessie/main amd64 Packages
        100 /var/lib/dpkg/status
samba-dev:
  Installed: (none)
  Candidate: 2:4.1.17+dfsg-2
  Version table:
     2:4.1.17+dfsg-2 0
        500 http://ftp.fr.debian.org/debian/ jessie/main amd64 Packages

Alternatively, you can use the dpkg command to get information about your current system. APT is the software that manages the download of packages, dependency analysis, etc. Dpkg is the low-level software that carries out the actual installation of a package file.

dpkg -l samba

This shows a line beginning with i if the package is installed, and a line beginning with u or p or nothing at all if the package is not installed.

$ dpkg -l samba samba-dev
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  samba          2:4.1.17+dfs amd64        SMB/CIFS file, print, and login s
dpkg-query: no packages found matching samba-dev

(dpkg-query is the dpkg subcommand that returns information about the package database.)

Note that if you just want to ensure that a package is installed, you can simply run

apt-get install samba

This won't do anything if the latest version of the package that's available in your distribution is already installed. It will install the package if it isn't installed yet, and it will upgrade it if you have an older version.