Provided by: dpkg_1.19.0.5ubuntu2_amd64 bug


       dpkg - package manager for Debian


       dpkg [option...] action


       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.


       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
       supported  actions  can  be  found  later on in the ACTIONS section. If any such action is
       encountered dpkg just runs dpkg-deb or dpkg-query with the parameters given to it, but  no
       specific  options  are currently passed to them, to use any such option the back-ends need
       to be called directly.


       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
              The package is not installed on your system.

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

              The installation of the package has  been  started,  but  not  completed  for  some

              The package is unpacked, but not configured.

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

              The package awaits trigger processing by another package.

              The package has been triggered.

              The package is correctly unpacked and configured.

   Package selection states
              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.

              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
       ok     A package marked ok is in a known state, but might need further processing.

              A  package  marked  reinstreq is broken and requires reinstallation. These packages
              cannot be removed, unless forced with option --force-remove-reinstreq.


       -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
              installation, 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
              installation, execute the postrm script of the old package. Note that  this  script
              is  executed  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
              specified, 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

              To  reconfigure  a  package  which   has   already   been   configured,   try   the
              dpkg-reconfigure(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
              processed.   If  package  names  are supplied only those packages' triggers will be
              processed, 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
              packages 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
              information 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
              information  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
              metadata 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.

       -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
              packages 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.

       --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  standard  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.

              Now obsolete and a no-op as dpkg will automatically forget uninstalled  unavailable
              packages  (since  dpkg 1.15.4), but only those that do not contain user information
              such as package selections.

              Erase the existing information about what packages are available.

       --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

              Set package selections using file read from stdin.  This  file  should  be  in  the
              format  “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.

              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.

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

              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
              massaged 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
              architecture 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

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

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

              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:

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

                     Supports epochs in version strings (since dpkg

                     Supports long filenames in deb(5) archives (since dpkg

                     Supports multiple Conflicts and Replaces (since dpkg

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

                     Supports versioned Provides (since dpkg 1.17.11).

       --validate-thing string
              Validate that the thing string has a correct syntax (since dpkg 1.18.16).   Returns
              0  if  the string is valid, 1 if the string is invalid but might be accepted in lax
              contexts, and 2 if the string is invalid.  The current list of  validatable  things

                     Validates the given package name (since dpkg 1.18.16).

                     Validates the given trigger name (since dpkg 1.18.16).

                     Validates the given architecture name (since dpkg 1.18.16).

                     Validates the given version (since dpkg 1.18.16).

       --compare-versions ver1 op ver2
              Compare  version  numbers,  where op is a binary operator. dpkg returns true (0) if
              the specified condition is satisfied, and false (1) otherwise. 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 confusing semantics. To
              illustrate: 0.1 < 0.1 evaluates to true.

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

              Give help about the --force-thing options.

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

              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
              -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.


       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
       configuration  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 ‘#’).

              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
              deconfiguration of the package which depended on the removed package.

       -Doctal, --debug=octal
              Switch debugging on. octal is formed by bitwise-oring 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

       --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
              message 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
              components 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
              reinstallation. This may, for example, cause parts of the package to remain on  the
              system, 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: 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
              version  in  the  package, even if the version in the package did not change (since
              dpkg 1.15.8).  If any of --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
              Currently this implies not performing file system syncs before file renames,  which
              is  known  to  cause  substantial  performance  degradation  on  some file systems,
              unfortunately the ones that require the safe I/O on the first place  due  to  their
              unreliable behaviour causing zero-length files on abrupt system crashes.

              Note:  For  ext4,  the  main  offender,  consider  using  instead  the mount option
              nodelalloc, 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.

              script-chrootless:  Run maintainer scrips without chroot(2)ing into instdir even if
              the package does not support this mode of operation (since dpkg 1.18.5).

              Warning: This can destroy your host system, use with extreme 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 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

              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 --record-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.

              Change  default  administrative  directory,  which  contains  many  files that give
              information about status of installed or uninstalled packages, etc.   (Defaults  to

              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
              running package's installation scripts, which means that the scripts see instdir as
              a root directory.  (Defaults to «/»)

              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.

              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
              multiple 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.

              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
              completely 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


              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.

              The filters are applied when unpacking the binary packages, and as such  only  have
              knowledge  of  the type of object currently being filtered (e.g. a normal file or a
              directory) and have not visibility of what objects will come next.   Because  these
              filters  have  side  effects  (in  contrast to find(1) filters), excluding an exact
              pathname that happens to be a directory object like /usr/share/doc  will  not  have
              the  desired  result,  and  only  that  pathname  will  be excluded (which could be
              automatically reincluded  if  the  code  sees  the  need).   Any  subsequent  files
              contained within that directory will fail to unpack.

              Hint: make sure the globs are not expanded by your shell.

       --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.

              Send  machine-readable  package  status  and  progress  information  to  the  shell
              command'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

              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

              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.

              YYYY-MM-DD HH:MM:SS conffile filename decision
                     For conffile changes where decision is either install or keep.

              Do not try to verify package signatures.

              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

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


       0      The  requested  action was successfully performed.  Or a check or assertion command
              returned true.

       1      A check or assertion command returned false.

       2      Fatal or unrecoverable error due to invalid  command-line  usage,  or  interactions
              with the system, such as accesses to the database, memory allocations, etc.


   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
              programs are not found, dpkg will abort.

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

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

       PAGER  The program dpkg will execute when displaying the conffiles.

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

              Sets  the  number  of  columns  dpkg  should  use  when  displaying formatted text.
              Currently only used by --list.

              Sets the color mode (since dpkg 1.18.5).  The currently accepted values  are:  auto
              (default), always and never.

   Internal environment
              Defined by dpkg on the maintainer script environment to indicate which installation
              to act on (since dpkg 1.18.5).  The value is intended to be prepended to  any  path
              maintainer  scripts  operate  on.  During normal operation, this variable is empty.
              When installing packages into a different instdir, dpkg normally invokes maintainer
              scripts    using    chroot(2)    and   leaves   this   variable   empty,   but   if
              --force-script-chrootless is specified then  the  chroot(2)  call  is  skipped  and
              instdir is non-empty.

              Defined  by  dpkg  on  the  maintainer  script  environment  to  indicate  the dpkg
              administrative directory to use (since dpkg 1.16.0).  This variable is  always  set
              to the current --admindir value.

              Defined  by  dpkg  on  the  shell  spawned  on  the  conffile prompt to examine the
              situation (since dpkg 1.15.6).  Current valid value: conffile-prompt.

              Defined by dpkg on the  shell  spawned  on  the  conffile  prompt  to  examine  the
              situation (since dpkg 1.15.6).  Contains the path to the old conffile.

              Defined  by  dpkg  on  the  shell  spawned  on  the  conffile prompt to examine the
              situation (since dpkg 1.15.6).  Contains the path to the new conffile.

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

              Defined  by  dpkg  on  the  maintainer  script  environment  to  the version of the
              currently running dpkg instance (since dpkg 1.14.17).

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

              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).

              Defined  by  dpkg  on  the  maintainer  script  environment to the architecture the
              package got built for (since dpkg 1.15.4).

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

              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).


              Configuration fragment files (since dpkg 1.15.4).

              Configuration file with default options.

              Default log file (see /etc/dpkg/dpkg.cfg 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.

              List of available packages.

              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 format and contents of a binary package are described in deb(5).


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


       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 for more details), for example:
            apt-cache dumpavail | dpkg --merge-avail
       or with dpkg 1.17.6 and earlier:
            apt-cache dumpavail >"$avail"
            dpkg --merge-avail "$avail"
            rm "$avail"
       you can install it with:
            dpkg --clear-selections
            dpkg --set-selections <myselections

       Note that this will not actually install or remove anything, but just  set  the  selection
       state on the requested packages. You will need some other application to actually download
       and install the requested packages. For example, run apt-get dselect-upgrade.

       Ordinarily, you will find that dselect(1) provides a more convenient  way  to  modify  the
       package selection states.


       Additional  functionality  can be gained by installing any of the following packages: apt,
       aptitude and debsums.


       aptitude(1), apt(1), dselect(1), dpkg-deb(1), dpkg-query(1), deb(5), deb-control(5),
       dpkg.cfg(5), and dpkg-reconfigure(8).


       See /usr/share/doc/dpkg/THANKS for the list of people who have contributed to dpkg.