UCF(1)                      Debian GNU/Linux manual                     UCF(1)

       ucf  -  Update Configuration File:  preserve user changes in configura-
       tion 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  (usu-
       ally under /etc) where the real configuration file lives, and is poten-
       tially 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  owner-
       ship  and  permission  of the New file as it is copied to the new loca-

       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,  pre-
       serving  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 cre-
       ated; 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 information.

       -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 vari-

       -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   configura-
              tion  file variable conf_source_dir.

       --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  tem-
              plate,  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

       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 contain-
       ing  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 com-
       plete, 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 file.

       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,

       /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 con-
       figuration 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 /usr/share/doc/ucf/examples):

       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 cur-
       rent  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-com-
       mon/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  <srivasta@debian.org>,
       for the Debian GNU/Linux system.

Debian                            May 30 2008                           UCF(1)
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