How To Satisfy Debian Dependencies Without Installing The Stupid Package (Shallow Thoughts)

Akkana's Musings on Open Source Computing, Science, and Nature.

Wed, 14 Nov 2012

How To Satisfy Debian Dependencies Without Installing The Stupid Package

(This is a guest post by David North.)

Debian developers tend to get overzealous in their dependency lists, probably to avoid constant headaches from fringe cases whose favorite programs fail because they also need some obscure library or package support (and yes, I'm talking to you, Ubuntu). But what if you don't want some goofy dependency (and the cascade of other crap it pulls in?)

As a small aside, aptitude/apt-get hold <pkg> is terrific if you just want to keep a package at a pre-horkage level, but for some obcure reason you can't "hold" a package that isn't installed. So that won't work as of 11/2012.

You can however generate an equivalent package with a higher version number and install it, which naturally blocks the offending package. Even better, the replacement package need do nothing at all other than satisfy the apt database. Even better, the whole thing is incredibly simple.

First install the "equivs" package. This will deliver two programs:

Officially you should start with 'equivs-control <:pkgname>' which will create a file 'pkgname' in the current directory. Inside are various fields but you only need eight and can simply delete the rest. Here's approximately what you should end up with for a fictional package "pkgname":

Section: misc
Priority: optional
Standards-Version: 3.9.2

Package: pkgname
Version: 1:42
Maintainer: Your Name <your@email.address>
Architecture: all
Description: fake pkgname to block a dumb dependency

The first three lines are just boilerplate, though you may have to increment the standards-version at some point if you reuse the file. No changes are needed now.

The pkgname does actually have to match the name of the package you want to block. The version must be higher than that of the target package. Maintainer need not be you, but it's a good idea to at least use a name you recognize as yourself. Architecture can be left as "all" unless you're doing something extra tricky. Description is not necessary but a good idea; put your notes here.

The only trick is the version. Note the 1:42 structure here. The first number is the "epoch" in debian-speak, and may or may not be used. In practice I've never seen an epoch greater than one, so I suggest using either 1 or 2 here rather than just leaving it blank. You can see the epoch number in a package when you use aptitude show <pkgname>. The version is the number immediately after the colon, and for safety's sake should be considerably larger than the version you're trying to block (to avoid future updates). I like to use "42" for obvious reasons unless the actual package version is too close. Factoid: if no "epoch" is indicated debian will assume epoch 0, which will not show up as a zero in a .deb (or in aptitude show) but rather as a blank. The version number will have no colon in this event.

Having done this, all you need do is issue the command 'equivs-build path-to-pkgname' (preferably from the same directory) and you get a fake deb to install with dpkg -i. Say goodbye to the dependency.

One more trick: once you have your file <pkgname> with the Eight Important Fields, you can pretty much skip using equivs-control. All it does is make the initial text file, and it will be easier to edit the one you already have with a new package name (and rename the file at the same time). Note, however, this handy file will not necessarily be useful on other debian-based systems or later installs, so running equivs-control after a big upgrade or moving to another distro is very good practice. If you compare the files and they have the same entries, great. If not, use the new ones.

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[ 10:50 Nov 14, 2012    More linux/install | permalink to this entry | comments ]
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