How do I get apt-get to ignore some dependencies?

Question

How do I make apt-get ignore some dependencies? For example, I wanted to install mailx so I can use it to send email from cron scripts/report-generating tools. However, installing mailx also installs exim4 and a whole bunch of dependencies (I already have Postfix installed) I don't really need and which I guess mailx can also live without.

How do I ignore some dependencies but still use apt-get since it's a nice tool?

Answer 1

You can try the --nodeps flag with apt-get.
Or download the package and install it using dpkg with the option --ignore-depends.

Answer 2

Since you installed postfix from source, you need to install a "dummy" package which will satisfy the mail-transport-agent dependency of mailx (or bsd-mailx). The "equivs" package in debian exists to create such a dummy package which you can install to tell dpkg "this dependency is satisfied"

The reason that telling dpkg to simply ignore dependencies is not a good solution, is that you are only telling dpkg/apt to ignore it for a single transaction, you can't tell it to ignore dependencies forever. Everytime you use apt it checks the dependencies on all packages

Answer 3

For the purposes of this, you could just install nail which I don't think has these dependencies?

apt-get install nail

Answer 4

On my debian system, bsd-mailx actually depends on default-mta | mail-transport-agent (you can check what a package depends on with apt-cache show <pkg> for anything in the archive or dpkg -s <pkg> for installed packages.

It may be that your postfix package doesn't have Provides: mail-transport-agent so apt doesn't realize you have an MTA installed. It would be worth filing a bug for that if it's an official package.

Answer 5

You can change the dependencies of a deb package like this:

1. Unpack deb: ar x golden-linux.deb (will create i.e. three files: debian-binary control.tar.gz data.tar.gz)
2. Unpack control archive: tar xzf control.tar.gz (will create: postinst postrm preinst prerm md5sums control)
3. Fix dependencies in control (use a text editor)
4. Repack control.tar.gz: tar c {post,pre}{inst,rm} md5sums control | gzip -c > control.tar.gz
5. Repack deb: ar rcs newpackage.deb debian-binary control.tar.gz data.tar.gz (order important! See [Note] )

[Note]: dpkg wouldn't be able to read the metadata of a package quickly if it had to search for where the data section ended!

Answer 6

I've been looking for this option on a Ubuntu 12.04 Server running Xen. In my domains I use the -virtual kernel, and apt persistently tried to install grub with every kernel package upgrade. Grub however is not needed inside the domU when using p[yv]grub.

I've been looking for the -nodeps option to apt-get as well, but it didn't work, so ended up uninstalling/purging grub* after each kernel upgrade.

After all, really reading a man page helps sometimes - it turns out a similar apt-get option on 12.04 seems to be --no-install-recommends, which actually works in this case, since grub is listed as 'recommended' in the package information (I guess so it is not a "real" dependency?).

I'm adding this here because in my case it solved a similar issue, and the hint for '--no-install-recommends' was not mentioned yet.

Answer 7

The dependencies required when you install a package through apt are listed by the package builder. So whoever built the mailx package decided that exim4 was a requirement (maybe mailx uses one of exim4's libraries?)

An alternative is to build mailx from source, and download the necessary libraries to do this. This will avoid involving the package manager.

Answer 8

After you install the package with the --ignore-depends option, go and edit the /var/lib/dpkg/status file, and remove whatever dependency you think is not needed. Just be very careful. In order a dep. to be required, it is more than likely to BE required

Answer 9

Well - don't.

Using other people's work is very important on the road to any success. When you build some software from source (tarball), you miss the opportunity to use the distro's package manager's work.

You won't get "free" updates. Most of the time none ever updates the packages they installed from source. Because they need to track the software for new versions, rebuild it and all the dependent programs (try to remember them).

You will have problems with other packages from your distribution's repos. This is exactly the case stated in the question: ubuntu has a great package manager and some very nice people maintaining the packages. And they have decided, that for the mailx program to work you need an MTA. So if you installed postfix from sources ubuntu wouldn't ask you to install exim.

If for some reason the maintenance of the server passes to some other person (e.g. your project becomes very successful and you decide to hire another guy to manager the servers while you are busy with other stuff) he will naturally expect to run dpkg --get-selections to get all the installed packages.

Try to use the distro's package management software as much as possible. Learn to build your own packages if you can't find one prebuilt and you'll become a better professional.