Re: cron.daily error for apt
E.1 Automatic handling of configuration files by dpkg
A package may contain a control information file called
conffiles. This file should be a list of filenames of configuration
files needing automatic handling, separated by newlines. The
filenames should be absolute pathnames, and the files referred to
should actually exist in the package.
When a package is upgraded dpkg will process the configuration files
during the configuration stage, shortly before it runs the package's
For each file it checks to see whether the version of the file
included in the package is the same as the one that was included in
the last version of the package (the one that is being upgraded
from); it also compares the version currently installed on the system
with the one shipped with the last version.
If neither the user nor the package maintainer has changed the file,
it is left alone. If one or the other has changed their version, then
the changed version is preferred - i.e., if the user edits their
file, but the package maintainer doesn't ship a different version,
the user's changes will stay, silently, but if the maintainer ships a
new version and the user hasn't edited it the new version will be
installed (with an informative message). If both have changed their
version the user is prompted about the problem and must resolve the
The comparisons are done by calculating the MD5 message digests of
the files, and storing the MD5 of the file as it was included in the
most recent version of the package.
When a package is installed for the first time dpkg will install the
file that comes with it, unless that would mean overwriting a file
already on the file system.
However, note that dpkg will not replace a conffile that was removed
by the user (or by a script). This is necessary because with some
programs a missing file produces an effect hard or impossible to
achieve in another way, so that a missing file needs to be kept that
way if the user did it.
Note that a package should not modify a dpkg-handled conffile in its
maintainer scripts. Doing this will lead to dpkg giving the user
confusing and possibly dangerous options for conffile update when the
package is upgraded.