dpkg is the base command for handling Debian packages on the system. If you have .deb packages, it is dpkg that allows installation or analysis of their contents. But this program only has a partial view of the Debian universe: it knows what is installed on the system, and whatever it is given on the command line, but knows nothing of the other available packages. As such, it will fail if a dependency is not met. Tools such as apt, on the contrary, will create a list of dependencies to install everything as automatically as possible.
dpkg is, above all, the tool for installing an already available Debian package (because it does not download anything). To do this, we use its -i or --install option.
Παράδειγμα 5.2. Installation of a package with dpkg
#dpkg -i man-db_2.7.6.1-2_amd64.deb(Reading database ... 110431 files and directories currently installed.) Preparing to unpack man-db_2.7.6.1-2_amd64.deb ... Unpacking man-db (2.7.6.1-2) over (2.7.6.1-1) ... Setting up man-db (2.7.6.1-2) ... Updating database of manual pages ... Processing triggers for mime-support (3.60) ...
dpkg; we know, thus, at what point any error may have occurred. The installation can also be effected in two stages: first unpacking, then configuration. apt-get takes advantage of this, limiting the number of calls to dpkg (since each call is costly, due to loading of the database in memory, especially the list of already installed files).
Παράδειγμα 5.3. Separate unpacking and configuration
#dpkg --unpack man-db_2.7.6.1-2_amd64.deb(Reading database ... 110431 files and directories currently installed.) Preparing to unpack man-db_2.7.6.1-2_amd64.deb ... Unpacking man-db (2.7.6.1-2) over (2.7.6.1-2) ... Processing triggers for mime-support (3.60) ... #dpkg --configure man-dbSetting up man-db (2.7.6.1-2) ... Updating database of manual pages ...
dpkg will fail to install a package and return an error; if the user orders it to ignore this, it will only issue a warning; it is for this reason that we have the different --force-* options. The dpkg --force-help command, or documentation of this command, will give a complete list of these options. The most frequent error, which you are bound to encounter sooner or later, is a file collision. When a package contains a file that is already installed by another package, dpkg will refuse to install it. The following messages will then appear:
Unpacking libgdm (from .../libgdm_3.8.3-2_amd64.deb) ...
dpkg: error processing /var/cache/apt/archives/libgdm_3.8.3-2_amd64.deb (--unpack):
trying to overwrite '/usr/bin/gdmflexiserver', which is also in package gdm3 3.4.1-9--force-overwrite, which tells dpkg to ignore this error and overwrite the file.
--force-* options, only --force-overwrite is likely to be used regularly. These options only exist for exceptional situations, and it is better to leave them alone as much as possible in order to respect the rules imposed by the packaging mechanism. Do not forget, these rules ensure the consistency and stability of your system.
dpkg with the -r or --remove option, followed by the name of a package, removes that package. This removal is, however, not complete: all of the configuration files, maintainer scripts, log files (system logs) and other user data handled by the package remain. That way disabling the program is easily done by uninstalling it, and it's still possible to quickly reinstall it with the same configuration. To completely remove everything associated with a package, use the -P or --purge option, followed by the package name.
Παράδειγμα 5.4. Removal and purge of the debian-cd package
#dpkg -r debian-cd(Reading database ... 112188 files and directories currently installed.) Removing debian-cd (3.1.20) ... #dpkg -P debian-cd(Reading database ... 111613 files and directories currently installed.) Purging configuration files for debian-cd (3.1.20) ...
dpkg options that query the internal database in order to obtain information. Giving first the long options and then corresponding short options (that will evidently take the same possible arguments) we cite --listfiles package (or -L), which lists the files installed by this package; --search file (or -S), which finds the package(s) containing the file; --status package (or -s), which displays the headers of an installed package; --list (or -l), which displays the list of packages known to the system and their installation status; --contents file.deb (or -c), which lists the files in the Debian package specified; --info file.deb (or -I), which displays the headers of this Debian package.
Παράδειγμα 5.5. Various queries with dpkg
$dpkg -L base-passwd/. /usr /usr/sbin /usr/sbin/update-passwd /usr/share /usr/share/base-passwd /usr/share/base-passwd/group.master /usr/share/base-passwd/passwd.master /usr/share/doc /usr/share/doc/base-passwd /usr/share/doc/base-passwd/README /usr/share/doc/base-passwd/changelog.gz /usr/share/doc/base-passwd/copyright /usr/share/doc/base-passwd/users-and-groups.html /usr/share/doc/base-passwd/users-and-groups.txt.gz /usr/share/doc-base /usr/share/doc-base/users-and-groups /usr/share/lintian /usr/share/lintian/overrides /usr/share/lintian/overrides/base-passwd /usr/share/man /usr/share/man/de /usr/share/man/de/man8 /usr/share/man/de/man8/update-passwd.8.gz /usr/share/man/es /usr/share/man/es/man8 /usr/share/man/es/man8/update-passwd.8.gz /usr/share/man/fr /usr/share/man/fr/man8 /usr/share/man/fr/man8/update-passwd.8.gz /usr/share/man/ja /usr/share/man/ja/man8 /usr/share/man/ja/man8/update-passwd.8.gz /usr/share/man/man8 /usr/share/man/man8/update-passwd.8.gz /usr/share/man/pl /usr/share/man/pl/man8 /usr/share/man/pl/man8/update-passwd.8.gz /usr/share/man/ru /usr/share/man/ru/man8 /usr/share/man/ru/man8/update-passwd.8.gz $dpkg -S /bin/datecoreutils: /bin/date $dpkg -s coreutilsPackage: coreutils Essential: yes Status: install ok installed Priority: required Section: utils Installed-Size: 15103 Maintainer: Michael Stone <mstone@debian.org> Architecture: amd64 Multi-Arch: foreign Version: 8.26-3 Replaces: mktemp, realpath, timeout Pre-Depends: libacl1 (>= 2.2.51-8), libattr1 (>= 1:2.4.46-8), libc6 (>= 2.17), libselinux1 (>= 2.1.13) Conflicts: timeout Description: GNU core utilities This package contains the basic file, shell and text manipulation utilities which are expected to exist on every operating system. . Specifically, this package includes: arch base64 basename cat chcon chgrp chmod chown chroot cksum comm cp csplit cut date dd df dir dircolors dirname du echo env expand expr factor false flock fmt fold groups head hostid id install join link ln logname ls md5sum mkdir mkfifo mknod mktemp mv nice nl nohup nproc numfmt od paste pathchk pinky pr printenv printf ptx pwd readlink realpath rm rmdir runcon sha*sum seq shred sleep sort split stat stty sum sync tac tail tee test timeout touch tr true truncate tsort tty uname unexpand uniq unlink users vdir wc who whoami yes Homepage: http://gnu.org/software/coreutils $dpkg -l 'b*'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 +++-====================-===============-===============-============================================= un backupninja <none> <none> (no description available) un backuppc <none> <none> (no description available) un baekmuk-ttf <none> <none> (no description available) un base <none> <none> (no description available) un base-config <none> <none> (no description available) ii base-files 9.9+deb9u1 amd64 Debian base system miscellaneous files ii base-passwd 3.5.43 amd64 Debian base system master password and group ii bash 4.4-5 amd64 GNU Bourne Again SHell [...] $dpkg -c /var/cache/apt/archives/gnupg_2.1.18-8~deb9u1_amd64.debdrwxr-xr-x root/root 0 2017-09-18 20:41 ./ drwxr-xr-x root/root 0 2017-09-18 20:41 ./usr/ drwxr-xr-x root/root 0 2017-09-18 20:41 ./usr/bin/ -rwxr-xr-x root/root 996648 2017-09-18 20:41 ./usr/bin/gpg -rwxr-xr-x root/root 3444 2017-09-18 20:41 ./usr/bin/gpg-zip -rwxr-xr-x root/root 161192 2017-09-18 20:41 ./usr/bin/gpgconf -rwxr-xr-x root/root 26696 2017-09-18 20:41 ./usr/bin/gpgparsemail -rwxr-xr-x root/root 76112 2017-09-18 20:41 ./usr/bin/gpgsplit -rwxr-xr-x root/root 158344 2017-09-18 20:41 ./usr/bin/kbxutil -rwxr-xr-x root/root 1081 2014-06-25 16:17 ./usr/bin/lspgpot -rwxr-xr-x root/root 2194 2017-09-18 20:41 ./usr/bin/migrate-pubring-from-classic-gpg -rwxr-xr-x root/root 14328 2017-09-18 20:41 ./usr/bin/watchgnupg drwxr-xr-x root/root 0 2017-09-18 20:41 ./usr/sbin/ -rwxr-xr-x root/root 3078 2017-09-18 20:41 ./usr/sbin/addgnupghome -rwxr-xr-x root/root 2219 2017-09-18 20:41 ./usr/sbin/applygnupgdefaults drwxr-xr-x root/root 0 2017-09-18 20:41 ./usr/share/ drwxr-xr-x root/root 0 2017-09-18 20:41 ./usr/share/doc/ drwxr-xr-x root/root 0 2017-09-18 20:41 ./usr/share/doc/gnupg/ -rw-r--r-- root/root 18964 2017-01-23 18:39 ./usr/share/doc/gnupg/DETAILS.gz [...] $dpkg -I /var/cache/apt/archives/gnupg_2.1.18-8~deb9u1_amd64.debnew debian package, version 2.0. size 1124042 bytes: control archive=2221 bytes. 1388 bytes, 24 lines control 2764 bytes, 43 lines md5sums Package: gnupg Source: gnupg2 Version: 2.1.18-8~deb9u1 Architecture: amd64 Maintainer: Debian GnuPG Maintainers <pkg-gnupg-maint@lists.alioth.debian.org> Installed-Size: 2088 Depends: gnupg-agent (= 2.1.18-8~deb9u1), libassuan0 (>= 2.0.1), libbz2-1.0, libc6 (>= 2.15), libgcrypt20 (>= 1.7.0), libgpg-error0 (>= 1.14), libksba8 (>= 1.3.4), libreadline7 (>= 6.0), libsqlite3-0 (>= 3.7.15), zlib1g (>= 1:1.1.4) Recommends: dirmngr (= 2.1.18-8~deb9u1), gnupg-l10n (= 2.1.18-8~deb9u1) Suggests: parcimonie, xloadimage Breaks: debsig-verify (<< 0.15), dirmngr (<< 2.1.18-8~deb9u1), gnupg2 (<< 2.1.11-7+exp1), libgnupg-interface-perl (<< 0.52-3), libgnupg-perl (<= 0.19-1), libmail-gnupg-perl (<= 0.22-1), monkeysphere (<< 0.38~), php-crypt-gpg (<= 1.4.1-1), python-apt (<= 1.1.0~beta4), python-gnupg (<< 0.3.8-3), python3-apt (<= 1.1.0~beta4) Replaces: gnupg2 (<< 2.1.11-7+exp1) Provides: gpg Section: utils Priority: optional Multi-Arch: foreign Homepage: https://www.gnupg.org/ Description: GNU privacy guard - a free PGP replacement GnuPG is GNU's tool for secure communication and data storage. It can be used to encrypt data and to create digital signatures. It includes an advanced key management facility and is compliant with the proposed OpenPGP Internet standard as described in RFC4880. [...]
dpkg keeps a log of all of its actions in /var/log/dpkg.log. This log is extremely verbose, since it details every one of the stages through which packages handled by dpkg go. In addition to offering a way to track dpkg's behavior, it helps, above all, to keep a history of the development of the system: one can find the exact moment when each package has been installed or updated, and this information can be extremely useful in understanding a recent change in behavior. Additionally, all versions being recorded, it is easy to cross-check the information with the changelog.Debian.gz for packages in question, or even with online bug reports.
Architecture field in their control information. This field can contain either “all” (for packages that are architecture independent) or the name of the architecture that it targets (like “amd64”, “armhf”, …). In the latter case, by default, dpkg will only accept to install the package if its architecture matches the host's architecture as returned by dpkg --print-architecture.
dpkg's multi-arch support allows users to define “foreign architectures” that can be installed on the current system. This is simply done with dpkg --add-architecture like in the example below. There is a corresponding dpkg --remove-architecture to drop support of a foreign architecture, but it can only be used when no packages of this architecture remain.
#dpkg --print-architectureamd64 #dpkg --print-foreign-architectures#dpkg -i gcc-6-base_6.3.0-18_armhf.debdpkg: error processing archive gcc-6-base_6.3.0-18_armhf.deb (--install): package architecture (armhf) does not match system (amd64) Errors were encountered while processing: gcc-6-base_6.3.0-18_armhf.deb #dpkg --add-architecture armhf#dpkg --add-architecture armel#dpkg --print-foreign-architecturesarmhf armel #dpkg -i gcc-6-base_6.3.0-18_armhf.debSelecting previously unselected package gcc-6-base:armhf. (Reading database ... 112000 files and directories currently installed.) Preparing to unpack gcc-6-base_6.3.0-18_armhf.deb ... Unpacking gcc-6-base:armhf (6.3.0-18) ... Setting up gcc-6-base:armhf (6.3.0-18) ... #dpkg --remove-architecture armhfdpkg: error: cannot remove architecture 'armhf' currently in use by the database #dpkg --remove-architecture armel#dpkg --print-foreign-architecturesarmhf
Multi-Arch: same” header field to tell the packaging system that the various architectures of the package can be safely co-installed (and that those packages can only satisfy dependencies of packages of the same architecture). The most important libraries have been converted since the introduction of multi-arch in Debian Wheezy, but there are many libraries that will likely never be converted unless someone specifically requests it (through a bug report for example).
$dpkg -s gcc-6-basedpkg-query: error: --status needs a valid package name but 'gcc-6-base' is not: ambiguous package name 'gcc-6-base' with more than one installed instance Use --help for help about querying packages. $dpkg -s gcc-6-base:amd64 gcc-6-base:armhf | grep ^MultiMulti-Arch: same Multi-Arch: same $dpkg -L libgcc1:amd64 |grep .so/lib/x86_64-linux-gnu/libgcc_s.so.1 $dpkg -S /usr/share/doc/gcc-6-base/copyrightgcc-6-base:amd64, gcc-6-base:armhf: /usr/share/doc/gcc-6-base/copyright
Multi-Arch: same packages must have their names qualified with their architecture to be unambiguously identifiable. They also have the possibility to share files with other instances of the same package; dpkg ensures that all packages have bit-for-bit identical files when they are shared. Last but not least, all instances of a package must have the same version. They must thus be upgraded together.
Multi-Arch: foreign” or a package whose architecture matches the one of the package declaring the dependency (in this dependency resolution process, architecture-independent packages are assumed to be of the same architecture than the host). A dependency can also be weakened to allow any architecture to fulfill it, with the package:any syntax, but foreign packages can only satisfy such a dependency if they are marked “Multi-Arch: allowed”.