tainer scripts

       dpkg-maintscript-helper command [parameter...] --  maint-script-parame-

       rm_conffile conffile [lastversion [package]]

       mv_conffile oldconffile newconffile [lastversion [package]]

       This program is designed to be run within maintainer scripts to achieve
       some tasks that dpkg can't (yet)  handle  natively  either  because  of
       design decisions or due to current limitations.

       Many of those tasks require coordinated actions from several maintainer
       scripts (preinst, postinst, prerm, postrm). To avoid mistakes the  same
       call  simply  needs to be put in all scripts and the program will auto-
       matically  adapt  its  behaviour  based  on  the  environment  variable
       DPKG_MAINTSCRIPT_NAME  and on the maintainer scripts arguments that you
       have to forward after a double dash.

       When upgrading a package, dpkg will not automatically remove a conffile
       (a  configuration  file for which dpkg should preserve user changes) if
       it is not present in the newer version. There are two principal reasons
       for this; the first is that the conffile could've been dropped by acci-
       dent and the next version could restore it, users wouldn't  want  their
       changes  thrown  away.  The  second  is to allow packages to transition
       files from a dpkg-maintained conffile to a file maintained by the pack-
       age's maintainer scripts, usually with a tool like debconf or ucf.

       This  means  that  if a package is intended to rename or remove a conf-
       file, it must explicitly do so and dpkg-maintscript-helper can be  used
       to  implement  graceful  deletion  and moving of conffiles within main-
       tainer scripts.

       If a conffile is completely removed, it should be  removed  from  disk,
       unless the user has modified it. If there are local modifications, they
       should be preserved. If the package upgrades aborts, the newly obsolete
       conffile should not disappear.

       All  of  this  is implemented by putting the following shell snippet in
       the preinst, postinst and postrm maintainer scripts:

           dpkg-maintscript-helper rm_conffile \
               conffile lastversion package -- "$@"

       conffile is the filename of the conffile to remove.  lastversion is the
       last  version  of  the package that contained the conffile (or the last
       version of the package that did not take care to  remove  the  obsolete
       conffile  if  this was not immediately implemented).  If lastversion is
       During purge, the postrm will also delete the .dpkg-bak file kept up to

       If  a  conffile is moved from one location to another, you need to make
       sure you move across any changes the user has made.  This  may  seem  a
       simple  change to the preinst script at first, however that will result
       in the user being prompted by dpkg to approve the conffile  edits  even
       though they are not responsible of them.

       Graceful  renaming  can  be  implemented by putting the following shell
       snippet in the preinst, postinst and postrm maintainer scripts:

           dpkg-maintscript-helper mv_conffile \
               oldconffile newconffile lastversion package -- "$@"

       oldconffile and newconffile are the old and new name of the conffile to
       rename.  lastversion  is the last version of the package that contained
       the conffile with the old name. If lastversion  is  empty  or  omitted,
       then  the operation is tried on every upgrade (note: it's safer to give
       the version and have the operation tried only  once).  package  is  the
       package    name,    it's    optional    as    it    will   default   to
       $DPKG_MAINTSCRIPT_PACKAGE (this variable is set by dpkg to the name  of
       the  package  acted upon). All the parameters of the maintainer scripts
       have to be forwarded to the program after "--".

       Current implementation: the preinst checks if  the  conffile  has  been
       modified,  if yes it's left on place otherwise it's renamed to oldconf-
       file.dpkg-remove.  On  configuration,  the  postinst  removes  oldconf-
       file.dpkg-remove  and renames oldconffile to newconffile if oldconffile
       is still available. On abort-upgrade/abort-install, the postrm  renames
       oldconffile.dpkg-remove back to oldconffile if required.

       Given  that  dpkg-maintscript-helper  is  used in the preinst, using it
       unconditionally requires a pre-dependency to ensure that  the  required
       version  of dpkg has been unpacked before. The required version depends
       on the command used, for rm_conffile and mv_conffile it is

           Pre-Depends: dpkg (>=

       But in many cases the operation done by the program is not critical for
       the package, and instead of using a pre-dependency we can call the pro-
       gram only if we know that the required command is supported by the cur-
       rently installed dpkg:

           if dpkg-maintscript-helper supports command; then
               dpkg-maintscript-helper command ...

       Copyright (C) 2010 Raphael Hertzog
       Copyright (C) 2008 Joey Hess
       Copyright (C) 2007 Guillem Jover
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