Provided by: dpkg_1.18.4ubuntu1.7_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
              A  package  marked  reinst-required  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.

       --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

              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).

              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
              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.

       --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).

       --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)
              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-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

       --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: 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
              version 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
              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.

              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 --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.

       --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  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.

              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).


   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 -l.

              Set  by  a  package  manager frontend to notify dpkg that it should not acquire the
              frontend lock (since dpkg 1.19.1).

   Internal environment
              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(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.

              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 following files are components of a binary package. See deb(5)  for  more  information
       about them:


       --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.