Editing Package manager (section)

===Maintenance of configuration===
Particularly troublesome with software [[upgrade]]s are upgrades of configuration files. Since package managers, at least on Unix systems, originated as extensions of [[file archiver|file archiving utilities]], they can usually only either overwrite or retain configuration files, rather than applying rules to them. There are exceptions to this that usually apply to kernel configuration (which, if broken, will render the computer unusable after a restart). Problems can be caused if the format of configuration files changes; for instance, if the old configuration file does not explicitly disable new options that should be disabled. Some package managers, such as [[Debian]]'s [[dpkg]], allow configuration during installation. In other situations, it is desirable to install packages with the default configuration and then overwrite this configuration, for instance, in [[Headless system|headless]] installations to a large number of computers. This kind of pre-configured installation is also supported by dpkg.