Provided by: ucf_3.0038+nmu1_all bug


       ucf - Update Configuration File:  preserve user changes in configuration files


       ucf [options] <New File> <Destination>

       ucf [options] --purge <Destination>


       This  utility provides a means of asking the user whether or not to accept new versions of
       configuration files provided by the package maintainer, with various  heuristics  designed
       to  minimize  interaction  time.  It uses debconf to interact with the user, as per Debian
       policy.  In the SYNOPSIS above, New file is the configuration  file  as  provided  by  the
       package  (either  shipped  with the package, or generated by the maintainer scripts on the
       fly), and Destination is the location (usually under /etc) where  the  real  configuration
       file  lives, and is potentially modified by the end user.  Since the files edited would be
       real files, and not symbolic links, ucf follows and resolves symbolic links before acting.
       As  far as possible, ucf attempts to preserve the ownership and permission of the New file
       as it is copied to the new location.

       This script attempts to provide conffile like handling for files installed under /etc  not
       shipped  in  a  Debian package, but handled by the postinst instead.  Debian policy states
       that files under /etc which are configuration files must preserve user changes,  and  this
       applies to files handled by maintainer scripts as well. Using ucf, one may ship a bunch of
       default configuration files somewhere in /usr ( /usr/share/<pkg> is a good location),  and
       maintain  files  in  /etc,  preserving  user  changes  and  in  general  offering the same
       facilities while upgrading that dpkg normally provides for “conffiles”

       Additionally, this script provides facilities for transitioning a file that had  not  been
       provided  conffile  like  protection  to  come under this schema, and attempts to minimize
       questions asked at install time. Indeed, the transitioning facility is better than the one
       offered  by  dpkg  while  transitioning a file from a non-conffile to conffile status. The
       second form in the SYNOPSIS above is for purging information about the configuration  file
       when the package is purged; and is critical for allowing smooth reinstallations.

       During  the  course  of  operations, when working with configuration files, ucf optionally
       creates copies of versions of the configuration file in question. For example, a file with
       the  suffix  ucf-old holds the old version of a configuration file replaced by ucf.  Also,
       copies of the configuration file with the suffixes ucf-new and ucf-dist  may  be  created;
       and  the  maintainer scripts should consider purging copies of the configuration file with
       these extensions during purge.


       -h, --help
              Print a short usage message

       -n, --no-action
              Dry run. Print the actions that would be taken if the script is invoked,  but  take
              no action.

       -d[n], --debug=[n]
              Set  the debug level to the (optional) level n (n defaults to 1). Please note there
              must be no spaces before the optional digit n.  This  turns  on  copious  debugging

       -p, --purge
              Removes all vestiges of the file from the state hashfile. This is required to allow
              a package to  be  reinstalled  after  it  is  purged;  since  otherwise,  the  real
              configuration file is removed, but it remains in the hash file; and on reinstall no
              action is taken, since the md5sum of the new file matches that in the hashfile.  In
              short,  remember  to  use  this  option  in the postrm for every configuration file
              managed by ucf when the package is  being  purged  (assuming  ucf  itself  exists).
              Note:  ucf  does not actually touch the file on disk in this operation, so any file
              removals are still the responsibility of the calling package.

       -v, --verbose
              Make the script be very verbose about setting internal variables.

       -s foo, --src-dir  foo
              Set the source directory (historical md5sums are expected to live in files and  sub
              directories of this directory) to foo. By default, the directory the new_file lives
              in is assumed to be the source directory. Setting this option overrides settings in
              the  environment  variable UCF_SOURCE_DIR, and in the  configuration  file variable

       --sum-file  foo
              Force the historical md5sums to be read from this file, rather than  defaulting  to
              living  in  the  source  directory.   Setting this option overrides settings in the
              environment variable UCF_OLD_MDSUM_FILE, and in the  configuration   file  variable

              This  turns on the option, during installation, for the user to be offered a chance
              to see a merge of the changes between old maintainer version and the new maintainer
              version  into the local copy of the configuration file. If the user likes what they
              see, they can ask to have these changes merged in.  This  allows  one  to  get  new
              upstream  changes  merged  in  even  while  retaining  local  modifications  to the
              configuration file. This is accomplished  by  taking  the  configuration  file  and
              stashing it in a cache area during registration, and using diff3 during the install
              (the stashed file name is a munged version of the full path  of  the  configuration
              file to avoid name space clashes).

              Indicate  that  it  is  ok  for  ucf to use an already running debconf instance for
              prompting (it has always been ok to use ucf when debconf is not running -- it shall
              invoke debconf as needed).

       --debconf-template  foo
              Instruct  ucf  to  use the named multiselect debconf template instead of the normal
              ucf-provided debconf template.  The caller is responsible  for  ensuring  that  the
              named  template exists and has a list of choices matching those for the default ucf
              template, and should set Choices-C: ${CHOICES} to ensure the returned values  match
              those from the default template.  Note that the choices must be different according
              to whether the --three-way option is also set.

       --state-dir /path/to/dir
              Set the state directory to /path/to/dir instead of the default /var/lib/ucf.   Used
              mostly for testing.


       The  most  common case usage is pretty simple: a single line invocation in the postinst on
       configure, and another single line  in  the  postrm  to  tell  ucf  to  forget  about  the
       configuration  file  on  purge (using the  --purge option) is all that is needed (assuming
       ucf is still on the system).

       It is recommended that you also register any file  being  managed  by  ucf  with  the  ucf
       registry;  this  associates the configuration file with the package it belongs to. This is
       done with a simple call  to  ucfr.   Users  may  then  query  the  association  between  a
       configuration file and the package using the tool ucfq.  Please see the appropriate manual
       pages for details.

       If a file maintained by maintainer scripts  is  being  transitioned  from  an  unprotected
       status  to  the  protection  afforded  by  the  script,  the  maintainer can help ease the
       transition by reducing the questions that may be asked at installation time. Specifically,
       questions  should  not  be asked if the file in question is an unmodified version that was
       one shipped in a previous version of this package; and the maintainer can help by  telling
       the script about the historical md5sums that published versions of this file contained.

       The way to do this is to either create a file called <New file>.md5sum, with one md5sum on
       each line, (the file names you use are ignored, except for the entry  named  default),  or
       create  a directory, called <New file>.md5sum.d, which should contain any number of files,
       each containing a single line, namely, the md5sum of a previous  version  of  <New  file>.
       The names of these files are not important, with one exception: The file called default is
       treated specially.  For example, the author personally uses either package version numbers
       or release code names, like 7.6.3, or potato.  If none of the historical md5sums match, we
       are almost certain that either the historical record of md5sums is not  complete,  or  the
       user has changed the configuration file.

   The default historical md5sum
       The  exception  to the rule about names mentioned earlier is that if no md5sums match, and
       if the file <New file>.md5sum.d/default exists, or if there is a line corresponding  to  a
       default  file in <New file>.md5sum, it shall be used as the default md5sum of the previous
       version of the package assumed to have been installed on this machine.  As  you  can  see,
       unless  there  are  limited  number  of  previously released packages (like just one), the
       maintainer is also making an informed guess, but the option is provided to the maintainer.

       If the file <New file>.md5sum, or the directory <New file>.md5sum.d  does  not  exist,  or
       none  of  the md5sums match, we test the installed <Destination> file to see whether it is
       the same as the <New file>.  If not, we ask the user whether they want us to  replace  the

       An  additional  facility is also offered: optionally, ucf can store one old version of the
       maintainers copy of the configuration file, and, on upgrade, calculate the changes made in
       the  maintainers  version  of  the  configuration  file, and apply that patch to the local
       version of the file (on user request, of course). There is also a preview  facility  where
       the user can inspect the results of such a merge, before asking the action to be taken.


       The  variable  UCF_FORCE_CONFFNEW,  if  set,  forces  the new file to always overwrite the
       installed destination file, while the variable UCF_FORCE_CONFFOLD, if set silently retains
       the installed file.  UCF_FORCE_CONFFMISS is only applicable when the installed destination
       file does not exist (perhaps due to user removal),and forces ucf to recreate  the  missing
       file  (the  default  behaviour  is  to honor the users wishes and not recreate the locally
       deleted file).


       This script creates the file new_file.md5sum, and it may copy the file (presumably shipped
       with the package) <New file> to its destination, <Destination>.

       /var/lib/ucf/hashfile,  and  /var/lib/ucf/hashfile.X,  where  X  is a small integer, where
       previous versions of the hashfile are stored.



       If the package foo wants to use ucf to handle  user  interaction  for  configuration  file
       foo.conf, a version of which is provided in the package as /usr/share/foo/configuration, a
       simple invocation of ucf in the post inst file is all that is needed:

       ucf /usr/share/foo/configuration /etc/foo.conf

       On purge, one should tell  ucf  to  forget  about  the  file  (see  detailed  examples  in

       ucf  --purge  /etc/foo.conf Please note that purge can also be used to make ucf forget the
       previous state of the files, and when the package is next installed or updated,  ucf  will
       ask  the user to replace the current cofiguration file. Do this if you want to change your
       decision to not update to a maintainer provided version of the configuration file.

       The motivation for this script was to provide conffile like handling for start  files  for
       emacs  lisp packages (for example, /etc/emacs21/site-start.d/50psgml-init.el ) These start
       files are not shipped with the package,  instead,  they  are  installed  during  the  post
       installation          configuration          phase          by          the         script
       /usr/lib/emacsen-common/emacs-package-install $package_name.

       This  script  is   meant   to   be   invoked   by   the   packages   install   script   at
       /usr/lib/emacsen-common/packages/install/$package_name   for  each  flavour  of  installed
       emacsen   by    calling    it    with    the    proper    values    of    new    file    (
       /usr/share/emacs/site-lisp/<pkg>/<pkg-init.el       ),      and      dest      file      (
       /etc/emacs21/site-start.d/50<pkg-init.el ), and it should do the rest.


       ucf.conf(5), ucfr(1), ucfq(1), and diff3(1).  The Debian Emacs policy,  shipped  with  the
       package emacsen-common.


       This  manual  page  was  written  Manoj  Srivastava  <>, for the Debian
       GNU/Linux system.