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dpkg(1)                                     dpkg suite                                    dpkg(1)

NAME
       dpkg - package manager for Debian

SYNOPSIS
       dpkg [option...] action

WARNING
       This  manual  is  intended for users wishing to understand dpkg's command line options and
       package states in more detail than that provided by dpkg --help.

       It should not be used by package maintainers wishing to understand how dpkg  will  install
       their  packages.  The descriptions of what dpkg does when installing and removing packages
       are particularly inadequate.

DESCRIPTION
       dpkg is a tool to install, build, remove and manage Debian packages. The primary and  more
       user-friendly  front-end  for  dpkg is aptitude(1). dpkg itself is controlled entirely via
       command line parameters, which consist of exactly one action and zero or more options. The
       action-parameter  tells  dpkg what to do and options control the behavior of the action in
       some way.

       dpkg can also be used as a front-end to dpkg-deb(1) and dpkg-query(1). The  list  of  sup‐
       ported actions can be found later on in the ACTIONS section. If any such action is encoun‐
       tered dpkg just runs dpkg-deb or dpkg-query with the parameters given to it, but  no  spe‐
       cific  options  are currently passed to them, to use any such option the back-ends need to
       be called directly.

INFORMATION ABOUT PACKAGES
       dpkg maintains some usable  information  about  available  packages.  The  information  is
       divided in three classes: states, selection states and flags. These values are intended to
       be changed mainly with dselect.

   Package states
       not-installed
              The package is not installed on your system.

       config-files
              Only the configuration files of the package exist on the system.

       half-installed
              The installation of the package has been started, but not completed for  some  rea‐
              son.

       unpacked
              The package is unpacked, but not configured.

       half-configured
              The  package  is unpacked and configuration has been started, but not yet completed
              for some reason.

       triggers-awaited
              The package awaits trigger processing by another package.

       triggers-pending
              The package has been triggered.

       installed
              The package is correctly unpacked and configured.

   Package selection states
       install
              The package is selected for installation.

       hold   A package marked to be on hold is not handled by dpkg, unless  forced  to  do  that
              with option --force-hold.

       deinstall
              The  package  is  selected  for  deinstallation  (i.e. we want to remove all files,
              except configuration files).

       purge  The package is selected to be purged (i.e. we want to remove everything from system
              directories, even configuration files).

   Package flags
       reinst-required
              A package marked reinst-required is broken and requires reinstallation. These pack‐
              ages cannot be removed, unless forced with option --force-remove-reinstreq.

ACTIONS
       -i, --install package-file...
              Install the package. If --recursive or -R option is  specified,  package-file  must
              refer to a directory instead.

              Installation consists of the following steps:

              1. Extract the control files of the new package.

              2.  If  another  version of the same package was installed before the new installa‐
              tion, execute prerm script of the old package.

              3. Run preinst script, if provided by the package.

              4. Unpack the new files, and at the same time back up the old  files,  so  that  if
              something goes wrong, they can be restored.

              5.  If  another  version of the same package was installed before the new installa‐
              tion, execute the postrm script of the old package. Note that this script  is  exe‐
              cuted after the preinst script of the new package, because new files are written at
              the same time old files are removed.

              6. Configure the package. See --configure for detailed information about  how  this
              is done.

       --unpack package-file...
              Unpack  the  package, but don't configure it. If --recursive or -R option is speci‐
              fied, package-file must refer to a directory instead.

       --configure package...|-a|--pending
              Configure a package which has been unpacked but  not  yet  configured.   If  -a  or
              --pending  is  given instead of package, all unpacked but unconfigured packages are
              configured.

              To reconfigure a package which has already been configured, try the  dpkg-reconfig‐
              ure(8) command instead.

              Configuring consists of the following steps:

              1.  Unpack  the  conffiles, and at the same time back up the old conffiles, so that
              they can be restored if something goes wrong.

              2. Run postinst script, if provided by the package.

       --triggers-only package...|-a|--pending
              Processes only triggers (since dpkg 1.14.17).  All pending triggers  will  be  pro‐
              cessed.   If  package names are supplied only those packages' triggers will be pro‐
              cessed, exactly once each where necessary. Use of this option may leave packages in
              the  improper triggers-awaited and triggers-pending states. This can be fixed later
              by running: dpkg --configure --pending.

       -r, --remove package...|-a|--pending
              Remove an installed package. This removes everything except  conffiles,  which  may
              avoid  having  to reconfigure the package if it is reinstalled later (conffiles are
              configuration files that are listed in the DEBIAN/conffiles control file).   If  -a
              or  --pending  is  given instead of a package name, then all packages unpacked, but
              marked to be removed in file /var/lib/dpkg/status, are removed.

              Removing of a package consists of the following steps:

              1. Run prerm script

              2. Remove the installed files

              3. Run postrm script

       -P, --purge package...|-a|--pending
              Purge an installed or already removed package. This removes  everything,  including
              conffiles.   If  -a or --pending is given instead of a package name, then all pack‐
              ages unpacked or removed, but marked to be purged in file /var/lib/dpkg/status, are
              purged.

              Note:  some  configuration  files might be unknown to dpkg because they are created
              and handled separately through the configuration scripts. In that case, dpkg  won't
              remove  them  by itself, but the package's postrm script (which is called by dpkg),
              has to take care of their removal during purge. Of course,  this  only  applies  to
              files  in  system directories, not configuration files written to individual users'
              home directories.

              Purging of a package consists of the following steps:

              1. Remove the package, if not already removed. See --remove for  detailed  informa‐
              tion about how this is done.

              2. Run postrm script.

       -V, --verify [package-name...]
              Verifies  the  integrity  of  package-name or all packages if omitted, by comparing
              information from the files installed by a package with the files metadata  informa‐
              tion  stored  in  the  dpkg  database (since dpkg 1.17.2).  The origin of the files
              metadata information in the database is the binary packages themselves. That  meta‐
              data gets collected at package unpack time during the installation process.

              Currently the only functional check performed is an md5sum verification of the file
              contents against the stored value in the files database.  It will only get  checked
              if  the database contains the file md5sum. To check for any missing metadata in the
              database, the --audit command can be used.

              The output format is selectable with the --verify-format option, which  by  default
              uses  the  rpm  format,  but that might change in the future, and as such, programs
              parsing this command output should be explicit about the format they expect.

       --update-avail [Packages-file]
       --merge-avail [Packages-file]
              Update dpkg's and dselect's idea of  which  packages  are  available.  With  action
              --merge-avail,  old  information  is  combined with information from Packages-file.
              With action --update-avail, old information is replaced with the information in the
              Packages-file.  The Packages-file distributed with Debian is simply named Packages.
              If the Packages-file argument is missing or named - then it will be read from stan‐
              dard  input  (since  dpkg  1.17.7).  dpkg keeps its record of available packages in
              /var/lib/dpkg/available.

              A simpler one-shot command to retrieve and update the  available  file  is  dselect
              update.  Note that this file is mostly useless if you don't use dselect but an APT-
              based frontend: APT has its own system to keep track of available packages.

       -A, --record-avail package-file...
              Update dpkg and dselect's idea of which packages  are  available  with  information
              from  the  package package-file. If --recursive or -R option is specified, package-
              file must refer to a directory instead.

       --forget-old-unavail
              Now obsolete and a no-op as dpkg will automatically forget uninstalled  unavailable
              packages (since dpkg 1.15.4).

       --clear-avail
              Erase the existing information about what packages are available.

       -C, --audit [package-name...]
              Performs database sanity and consistency checks for package-name or all packages if
              omitted (per package checks since dpkg 1.17.10).  For example, searches  for  pack‐
              ages  that  have been installed only partially on your system or that have missing,
              wrong or obsolete control data or files. dpkg will suggest what to do with them  to
              get them fixed.

       --get-selections [package-name-pattern...]
              Get  list  of  package  selections, and write it to stdout. Without a pattern, non-
              installed packages (i.e. those which have  been  previously  purged)  will  not  be
              shown.

       --set-selections
              Set  package selections using file read from stdin. This file should be in the for‐
              mat “package state”, where state is one of install, hold, deinstall or purge. Blank
              lines and comment lines beginning with ‘#’ are also permitted.

              The  available file needs to be up-to-date for this command to be useful, otherwise
              unknown packages will be  ignored  with  a  warning.  See  the  --update-avail  and
              --merge-avail commands for more information.

       --clear-selections
              Set  the  requested  state  of every non-essential package to deinstall (since dpkg
              1.13.18).  This is intended to be  used  immediately  before  --set-selections,  to
              deinstall any packages not in list given to --set-selections.

       --yet-to-unpack
              Searches  for  packages  selected for installation, but which for some reason still
              haven't been installed.

       --predep-package
              Print a single package which is the target of one or more relevant pre-dependencies
              and has itself no unsatisfied pre-dependencies.

              If such a package is present, output it as a Packages file entry, which can be mas‐
              saged as appropriate.

              Returns 0 when a package is printed, 1 when no suitable package is available and  2
              on error.

       --add-architecture architecture
              Add  architecture  to the list of architectures for which packages can be installed
              without using --force-architecture (since dpkg 1.16.2).  The architecture  dpkg  is
              built for (i.e. the output of --print-architecture) is always part of that list.

       --remove-architecture architecture
              Remove  architecture  from  the  list  of  architectures  for which packages can be
              installed without using --force-architecture (since dpkg 1.16.2). If the  architec‐
              ture is currently in use in the database then the operation will be refused, except
              if --force-architecture is specified. The architecture dpkg is built for (i.e.  the
              output of --print-architecture) can never be removed from that list.

       --print-architecture
              Print architecture of packages dpkg installs (for example, “i386”).

       --print-foreign-architectures
              Print  a  newline-separated  list  of the extra architectures dpkg is configured to
              allow packages to be installed for (since dpkg 1.16.2).

       --assert-feature
              Asserts that dpkg supports the requested feature.  Returns  0  if  the  feature  is
              fully  supported,  1 if the feature is known but dpkg cannot provide support for it
              yet, and 2 if the feature is unknown.  The current list of assertable features is:

              support-predepends
                     Supports the Pre-Depends field (since dpkg 1.1.0).

              working-epoch
                     Supports epochs in version strings (since dpkg 1.4.0.7).

              long-filenames
                     Supports long filenames in deb(5) archives (since dpkg 1.4.1.17).

              multi-conrep
                     Supports multiple Conflicts and Replaces (since dpkg 1.4.1.19).

              multi-arch
                     Supports multi-arch fields and semantics (since dpkg 1.16.2).

              versioned-provides
                     Supports versioned Provides (since dpkg 1.17.11).

       --compare-versions ver1 op ver2
              Compare version numbers, where op is a binary operator. dpkg returns success  (zero
              result)  if the specified condition is satisfied, and failure (nonzero result) oth‐
              erwise. There are two groups of operators, which differ in how they treat an  empty
              ver1 or ver2. These treat an empty version as earlier than any version: lt le eq ne
              ge gt. These treat an empty version as later than any version:  lt-nl  le-nl  ge-nl
              gt-nl.  These are provided only for compatibility with control file syntax: < << <=
              = >= >> >. The < and > operators are obsolete and should not be used, due  to  con‐
              fusing semantics. To illustrate: 0.1 < 0.1 evaluates to true.

       -?, --help
              Display a brief help message.

       --force-help
              Give help about the --force-thing options.

       -Dh, --debug=help
              Give help about debugging options.

       --version
              Display dpkg version information.

       dpkg-deb actions
              See dpkg-deb(1) for more information about the following actions.

              -b, --build directory [archive|directory]
                  Build a deb package.
              -c, --contents archive
                  List contents of a deb package.
              -e, --control archive [directory]
                  Extract control-information from a package.
              -x, --extract archive directory
                  Extract the files contained by package.
              -X, --vextract archive directory
                  Extract and display the filenames contained by a
                  package.
              -f, --field  archive [control-field...]
                  Display control field(s) of a package.
              --ctrl-tarfile archive
                  Output the control tar-file contained in a Debian package.
              --fsys-tarfile archive
                  Output the filesystem tar-file contained by a Debian package.
              -I, --info archive [control-file...]
                  Show information about a package.

       dpkg-query actions
              See dpkg-query(1) for more information about the following actions.

              -l, --list package-name-pattern...
                  List packages matching given pattern.
              -s, --status package-name...
                  Report status of specified package.
              -L, --listfiles package-name...
                  List files installed to your system from package-name.
              -S, --search filename-search-pattern...
                  Search for a filename from installed packages.
              -p, --print-avail package-name...
                  Display details about package-name, as found in
                  /var/lib/dpkg/available. Users of APT-based frontends
                  should use apt-cache show package-name instead.

OPTIONS
       All  options  can be specified both on the command line and in the dpkg configuration file
       /etc/dpkg/dpkg.cfg or fragment files (with names matching this  shell  pattern  '[0-9a-zA-
       Z_-]*')  on the configuration directory /etc/dpkg/dpkg.cfg.d/. Each line in the configura‐
       tion file is either an option (exactly the same as the command  line  option  but  without
       leading hyphens) or a comment (if it starts with a #).

       --abort-after=number
              Change after how many errors dpkg will abort. The default is 50.

       -B, --auto-deconfigure
              When  a  package  is removed, there is a possibility that another installed package
              depended on the removed package. Specifying this option will cause automatic decon‐
              figuration of the package which depended on the removed package.

       -Doctal, --debug=octal
              Switch debugging on. octal is formed by bitwise-orring desired values together from
              the list below (note that these values may  change  in  future  releases).  -Dh  or
              --debug=help display these debugging values.

                  Number   Description
                       1   Generally helpful progress information
                       2   Invocation and status of maintainer scripts
                      10   Output for each file processed
                     100   Lots of output for each file processed
                      20   Output for each configuration file
                     200   Lots of output for each configuration file
                      40   Dependencies and conflicts
                     400   Lots of dependencies/conflicts output
                   10000   Trigger activation and processing
                   20000   Lots of output regarding triggers
                   40000   Silly amounts of output regarding triggers
                    1000   Lots of drivel about e.g. the dpkg/info dir
                    2000   Insane amounts of drivel

       --force-things
       --no-force-things, --refuse-things
              Force or refuse (no-force and refuse mean the same thing) to do some things. things
              is a comma separated list of things specified below. --force-help displays  a  mes‐
              sage describing them.  Things marked with (*) are forced by default.

              Warning:  These  options are mostly intended to be used by experts only. Using them
              without fully understanding their effects may break your whole system.

              all: Turns on (or off) all force options.

              downgrade(*): Install a package, even if newer version of it is already installed.

              Warning: At present dpkg does not do any  dependency  checking  on  downgrades  and
              therefore  will  not  warn you if the downgrade breaks the dependency of some other
              package. This can have serious side effects, downgrading  essential  system  compo‐
              nents can even make your whole system unusable. Use with care.

              configure-any:  Configure  also any unpacked but unconfigured packages on which the
              current package depends.

              hold: Process packages even when marked “hold”.

              remove-reinstreq: Remove a package, even if it's broken and marked to require rein‐
              stallation. This may, for example, cause parts of the package to remain on the sys‐
              tem, which will then be forgotten by dpkg.

              remove-essential: Remove, even if the package is  considered  essential.  Essential
              packages  contain  mostly  very  basic Unix commands. Removing them might cause the
              whole system to stop working, so use with caution.

              depends: Turn all dependency problems into warnings.

              depends-version: Don't care about versions when checking dependencies.

              breaks: Install, even if this would break another package (since dpkg 1.14.6).

              conflicts: Install, even if it conflicts with another package. This  is  dangerous,
              for it will usually cause overwriting of some files.

              confmiss:  If  a  conffile  is  missing  and the version in the package did change,
              always install the missing conffile without prompting. This is dangerous, since  it
              means not preserving a change (removing) made to the file.

              confnew: If a conffile has been modified and the version in the package did change,
              always install the new version without prompting,  unless  the  --force-confdef  is
              also specified, in which case the default action is preferred.

              confold: If a conffile has been modified and the version in the package did change,
              always keep the old version without prompting, unless the --force-confdef  is  also
              specified, in which case the default action is preferred.

              confdef: If a conffile has been modified and the version in the package did change,
              always choose the default action without prompting. If there is no  default  action
              it will stop to ask the user unless --force-confnew or --force-confold is also been
              given, in which case it will use that to decide the final action.

              confask: If a conffile has been modified always offer to replace it with  the  ver‐
              sion  in the package, even if the version in the package did not change (since dpkg
              1.15.8).   If  any  of  --force-confmiss,  --force-confnew,   --force-confold,   or
              --force-confdef is also given, it will be used to decide the final action.

              overwrite: Overwrite one package's file with another's file.

              overwrite-dir: Overwrite one package's directory with another's file.

              overwrite-diverted: Overwrite a diverted file with an undiverted version.

              unsafe-io: Do not perform safe I/O operations when unpacking (since dpkg 1.15.8.6).
              Currently this implies not performing file system syncs before file renames,  which
              is  known to cause substantial performance degradation on some file systems, unfor‐
              tunately the ones that require the safe I/O on the first place due to their unreli‐
              able behaviour causing zero-length files on abrupt system crashes.

              Note: For ext4, the main offender, consider using instead the mount option nodelal‐
              loc, which will fix both the performance degradation and the  data  safety  issues,
              the latter by making the file system not produce zero-length files on abrupt system
              crashes with any software not doing syncs before atomic renames.

              Warning: Using this option might improve performance at the cost  of  losing  data,
              use with care.

              architecture: Process even packages with wrong or no architecture.

              bad-version: Process even packages with wrong versions (since dpkg 1.16.1).

              bad-path: PATH is missing important programs, so problems are likely.

              not-root: Try to (de)install things even when not root.

              bad-verify: Install a package even if it fails authenticity check.

       --ignore-depends=package,...
              Ignore dependency-checking for specified packages (actually, checking is performed,
              but only warnings about conflicts are given, nothing else).

       --no-act, --dry-run, --simulate
              Do everything which is supposed to be done, but don't write any  changes.  This  is
              used to see what would happen with the specified action, without actually modifying
              anything.

              Be sure to give --no-act before the action-parameter, or  you  might  end  up  with
              undesirable  results.  (e.g. dpkg --purge foo --no-act will first purge package foo
              and then try to purge package --no-act, even though you  probably  expected  it  to
              actually do nothing)

       -R, --recursive
              Recursively  handle  all  regular  files  matching pattern *.deb found at specified
              directories and all of its subdirectories. This can be used with -i, -A, --install,
              --unpack and --avail actions.

       -G     Don't  install  a  package  if  a  newer  version  of  the  same package is already
              installed. This is an alias of --refuse-downgrade.

       --admindir=dir
              Change default administrative directory, which contains many files that give infor‐
              mation  about  status  of  installed  or  uninstalled  packages, etc.  (Defaults to
              /var/lib/dpkg)

       --instdir=dir
              Change default installation directory which refers to the directory where  packages
              are  to be installed. instdir is also the directory passed to chroot(2) before run‐
              ning package's installation scripts, which means that the scripts see instdir as  a
              root directory.  (Defaults to /)

       --root=dir
              Changing root changes instdir to dir and admindir to dir/var/lib/dpkg.

       -O, --selected-only
              Only process the packages that are selected for installation. The actual marking is
              done with dselect or by dpkg, when it handles packages. For example, when a package
              is removed, it will be marked selected for deinstallation.

       -E, --skip-same-version
              Don't install the package if the same version of the package is already installed.

       --pre-invoke=command
       --post-invoke=command
              Set  an  invoke hook command to be run via “sh -c” before or after the dpkg run for
              the unpack, configure, install, triggers-only, remove, purge, add-architecture  and
              remove-architecture   dpkg   actions   (since  dpkg  1.15.4;  add-architecture  and
              remove-architecture actions since dpkg 1.17.19). This option can be specified  mul‐
              tiple  times.  The order the options are specified is preserved, with the ones from
              the   configuration   files   taking   precedence.    The   environment    variable
              DPKG_HOOK_ACTION  is set for the hooks to the current dpkg action. Note: front-ends
              might call dpkg several times per invocation, which might run the hooks more  times
              than expected.

       --path-exclude=glob-pattern
       --path-include=glob-pattern
              Set  glob-pattern  as a path filter, either by excluding or re-including previously
              excluded paths matching the specified patterns during install (since dpkg 1.15.8).

              Warning: take into account that depending on the  excluded  paths  you  might  com‐
              pletely break your system, use with caution.

              The  glob  patterns  use the same wildcards used in the shell, were ‘*’ matches any
              sequence of characters, including the empty string  and  also  ‘/’.   For  example,
              «/usr/*/READ*»  matches «/usr/share/doc/package/README».  As usual, ‘?’ matches any
              single character (again, including ‘/’).  And ‘[’ starts a character  class,  which
              can  contain  a  list  of  characters, ranges and complementations. See glob(7) for
              detailed information about globbing. Note: the  current  implementation  might  re-
              include more directories and symlinks than needed, to be on the safe side and avoid
              possible unpack failures, future work might fix this.

              This can be used to remove all paths except some particular ones;  a  typical  case
              is:

              --path-exclude=/usr/share/doc/*
              --path-include=/usr/share/doc/*/copyright

              to remove all documentation files except the copyright files.

              These two options can be specified multiple times, and interleaved with each other.
              Both are processed in the given order, with the last rule that matches a file  name
              making the decision.

       --verify-format format-name
              Sets the output format for the --verify command (since dpkg 1.17.2).

              The  only  currently  supported  output format is rpm, which consists of a line for
              every path that failed any check.  The lines start with 9 characters to report each
              specific  check result, a ‘?’ implies the check could not be done (lack of support,
              file permissions, etc), ‘.’ implies the check passed, and an alphanumeric character
              implies a specific check failed; the md5sum verification failure (the file contents
              have changed) is denoted with a ‘5’ on the third character.  The line  is  followed
              by  a space and an attribute character (currently ‘c’ for conffiles), another space
              and the pathname.

       --status-fd n
              Send machine-readable package status and progress information to file descriptor n.
              This  option  can  be  specified  multiple  times. The information is generally one
              record per line, in one of the following forms:

              status: package: status
                     Package status changed; status is as in the status file.

              status: package : error : extended-error-message
                     An error occurred. Any possible newlines in extended-error-message  will  be
                     converted to spaces before output.

              status: file : conffile-prompt : 'real-old' 'real-new' useredited distedited
                     User is being asked a conffile question.

              processing: stage: package
                     Sent just before a processing stage starts. stage is one of upgrade, install
                     (both sent before unpacking), configure, trigproc, disappear, remove, purge.

       --status-logger=command
              Send machine-readable package status and progress information  to  the  shell  com‐
              mand's  standard input, to be run via “sh -c” (since dpkg 1.16.0).  This option can
              be specified multiple times.  The output format used is the same as in --status-fd.

       --log=filename
              Log status  change  updates  and  actions  to  filename,  instead  of  the  default
              /var/log/dpkg.log.  If  this  option  is given multiple times, the last filename is
              used. Log messages are of the form ‘YYYY-MM-DD HH:MM:SS startup type  command’  for
              each  dpkg  invocation where type is archives (with a command of unpack or install)
              or packages (with a command of configure, triggers-only, remove or  purge);  ‘YYYY-
              MM-DD  HH:MM:SS  status  state  pkg  installed-version’  for status change updates;
              ‘YYYY-MM-DD HH:MM:SS action pkg installed-version  available-version’  for  actions
              where  action is one of install, upgrade, configure, trigproc, disappear, remove or
              purge; and ‘YYYY-MM-DD HH:MM:SS conffile filename decision’  for  conffile  changes
              where decision is either install or keep.

       --no-debsig
              Do not try to verify package signatures.

       --no-triggers
              Do  not  run  any  triggers  in this run (since dpkg 1.14.17), but activations will
              still be recorded.  If used with --configure  package  or  --triggers-only  package
              then  the  named  package postinst will still be run even if only a triggers run is
              needed. Use of this option may leave packages in the improper triggers-awaited  and
              triggers-pending  states.  This  can  be  fixed  later by running: dpkg --configure
              --pending.

       --triggers
              Cancels a previous --no-triggers (since dpkg 1.14.17).

ENVIRONMENT
   External environment
       PATH   This variable is expected to be defined in the environment and point to the  system
              paths  where several required programs are to be found. If it's not set or the pro‐
              grams are not found, dpkg will abort.

       HOME   If set, dpkg will use it as the directory from which to read the user specific con‐
              figuration file.

       TMPDIR If  set,  dpkg  will use it as the directory in which to create temporary files and
              directories.

       PAGER  The program dpkg will execute when displaying the conffiles.

       SHELL  The program dpkg will execute when starting a new interactive shell.

       COLUMNS
              Sets the number of columns dpkg should use when  displaying  formatted  text.  Cur‐
              rently only used by -l.

   Internal environment
       DPKG_SHELL_REASON
              Defined  by  dpkg on the shell spawned on the conffile prompt to examine the situa‐
              tion (since dpkg 1.15.6).  Current valid value: conffile-prompt.

       DPKG_CONFFILE_OLD
              Defined by dpkg on the shell spawned on the conffile prompt to examine  the  situa‐
              tion (since dpkg 1.15.6).  Contains the path to the old conffile.

       DPKG_CONFFILE_NEW
              Defined  by  dpkg on the shell spawned on the conffile prompt to examine the situa‐
              tion (since dpkg 1.15.6).  Contains the path to the new conffile.

       DPKG_HOOK_ACTION
              Defined by dpkg on the shell spawned when  executing  a  hook  action  (since  dpkg
              1.15.4).  Contains the current dpkg action.

       DPKG_RUNNING_VERSION
              Defined  by  dpkg  on  the maintainer script environment to the version of the cur‐
              rently running dpkg instance (since dpkg 1.14.17).

       DPKG_MAINTSCRIPT_PACKAGE
              Defined by dpkg on the maintainer script environment  to  the  (non-arch-qualified)
              package name being handled (since dpkg 1.14.17).

       DPKG_MAINTSCRIPT_PACKAGE_REFCOUNT
              Defined  by  dpkg  on  the  maintainer  script environment to the package reference
              count, i.e. the number of package instances with a state greater than not-installed
              (since dpkg 1.17.2).

       DPKG_MAINTSCRIPT_ARCH
              Defined  by dpkg on the maintainer script environment to the architecture the pack‐
              age got built for (since dpkg 1.15.4).

       DPKG_MAINTSCRIPT_NAME
              Defined by dpkg on the maintainer script environment to the name of the script run‐
              ning, one of preinst, postinst, prerm or postrm (since dpkg 1.15.7).

       DPKG_MAINTSCRIPT_DEBUG
              Defined by dpkg on the maintainer script environment to a value (‘0’ or ‘1’) noting
              whether debugging has been requested (with the --debug option) for  the  maintainer
              scripts (since dpkg 1.18.4).

FILES
       /etc/dpkg/dpkg.cfg.d/[0-9a-zA-Z_-]*
              Configuration fragment files (since dpkg 1.15.4).

       /etc/dpkg/dpkg.cfg
              Configuration file with default options.

       /var/log/dpkg.log
              Default log file (see /etc/dpkg/dpkg.cfg(5) and option --log).

       The  other  files  listed below are in their default directories, see option --admindir to
       see how to change locations of these files.

       /var/lib/dpkg/available
              List of available packages.

       /var/lib/dpkg/status
              Statuses of available packages. This file  contains  information  about  whether  a
              package  is  marked  for  removing or not, whether it is installed or not, etc. See
              section INFORMATION ABOUT PACKAGES for more info.

              The status file is backed up daily in /var/backups. It can be useful if  it's  lost
              or corrupted due to filesystems troubles.

       The  following  files  are components of a binary package. See deb(5) for more information
       about them:
              control
              conffiles
              preinst
              postinst
              prerm
              postrm
              triggers

BUGS
       --no-act usually gives less information than might be helpful.

EXAMPLES
       To list installed packages related to the editor vi(1) (note that dpkg-query does not load
       the  available  file  anymore by default, and the dpkg-query --load-avail option should be
       used instead for that):
            dpkg -l '*vi*'

       To see the entries in /var/lib/dpkg/available of two packages:
            dpkg --print-avail elvis vim | less

       To search the listing of packages yourself:
            less /var/lib/dpkg/available

       To remove an installed elvis package:
            dpkg -r elvis

       To install a package, you first need to find it in an archive or CDROM. The available file
       shows that the vim package is in section editors:
            cd /media/cdrom/pool/main/v/vim
            dpkg -i vim_4.5-3.deb

       To make a local copy of the package selection states:
            dpkg --get-selections >myselections

       You  might  transfer this file to another computer, and after having updated the available
       file    there    with    your    package    manager    frontend     of     choice     (see
       https://wiki.debian.org/Teams/Dpkg/FAQ for more details), for example:
            apt-cache dumpavail | dpkg --merge-avail
       or with dpkg 1.17.6 and earlier:
            avail=`mktemp`
            apt-cache dumpavail >"$avail"
            dpkg --merge-avail "$avail"
            rm "$avail"
       you can install it with:
            dpkg --clear-selections
            dpkg --set-selections 

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