Issue: While updating a Debian package, wordpress in this case, the process fails mid-way: a conffile name is not an absolute pathname. Bummer!
Preparing to unpack .../wordpress_5.8.1+dfsg1-2_all.deb ... dpkg: error processing /var/cache/apt/archives/wordpress_5.8.1+dfsg1-2_all.deb (--unpack): conffile name »remove-on-upgrade /etc/wordpress/wp-config.php« is not an absolute pathname Errors were encountered while processing: /var/cache/apt/archives/wordpress_5.8.1+dfsg1-2_all.deb
Debian-helpers bark at the remove-on-upgrade tag. Usually, this kind of stuff means, the system packages in general are not up-to-date and in this particular case debian-helpers are out of date: They just lack support for remove-on-upgrade. Well, keeping systems always up-to-date is a daunting task. This issue is equally taking it’s toll.
Solution: Upon facing this issue, you can either
- upgrade system packages before upgrading wordpress (or any other non-essential package) or
- unpack the to-be-installed package and fixing the issue by hand:
Edit DEBIAN/conffiles:
~# grep remove-on-upgrade DEBIAN/conffiles remove-on-upgrade /etc/wordpress/wp-config.php
Just remove the remove-on-upgrade tag and any leading whitespace and you’re good to go.
Reasoning: Chances are, the system packages are outdated. In this case dpkg has no notion of a remove-on-upgrade tag in the package’s conffiles config file (yikes!) as of version 1.19-7. After upgrading[ dpkg], as of version 1.20.9, dpkg knows about this tag (the only one existing to date).