On CoreOS, Git and Perl

Posted by Katie McLaughlin on November 20, 2014

“Git submodule init requires perl. Cannot install Perl, am running CoreOS. Sadness.”

  • https://twitter.com/glasnt/status/534926961957535744

I’ve been recently pushed head first into the land of CoreOS and Docker, attempting to get a consolidation of efforts together to get our Haskell project widgets in an automatically deployable, scalable state, and I hit this particular issue.

CoreOS doesn’t come with any scripting languages. Which is a good thing, because it means CoreOS is very light.

But it becomes an issue when executing git submodule ... requires Perl.

$ git submodule init
/usr/libexec/git-core/git-submodule: line 159: perl: command not found

So I thought “why is this so?”, and executed a command I never thought I’d have to do:

git clone https://code.google.com/p/git-core/

A few minutes in the code base and I find that there’s a little shell file called git-submodule.sh which has a function called module_list that embeds raw Perl in order to do some fancy pattern matching. This method is used by about half the functions in the file, so it’s a little bit important.

The INSTALL file mentions that Perl is just in just a little bit of the system, but fails to mention this submodule limitation.

The work around? git clone <submodule repo> in my repo.

The actual fix? Work out how/if you can do the same sort of functionality in pure shell.

Probaility of success - probably limited.

It’s always interesting, however, to see that even some of the fundemental Linux constructs are just shell, Perl and C all the way down.