UnionFS in Gentoo: It Aint Easy

The following text contains description that may be disturbing for newbies. Reader’s discretion is advised.

Folks, I can’t believe it. UnionFS is perhaps one of the most widely used undistributed file-systems I’ve ever seen. To prove my point: I’m sure all of you have heard of it, but when was the last time you installed and used it on your production machine?

Well, maybe I’m wrong and you guys’ve already taken the leap (or developers of your distribution of choice have) and you’ve already got unionfs doing all sorts of file system backflips for you, but I had yet to install, er, patch in support for it.

Turns out it’s pretty simple… sort of. All you have to do is download a patchfile for your relevant kernel version, patch your kernel source, compile that, and then watch it fail, google the error, find the solution, realize that that particular mailing list archiver does a terrible job of retaining all the right spacing, find a different page with the same message, patch your kernel again (probably by hand since the patchfile given doesn’t work on all kernel versions), and compile that one last time.

I’ve yet to reboot and see if UnionFS works (going to back everything up first), but I’m guessing that it’ll work for the most part. I don’t plan on it writing back to my file-system, so I shouldn’t see any corruption, but I’ve heard bad things about UnionFS, enough to make me wary.

Update (2009/04/04): Well, a month has gone by and so far everything has run beautifully. Have yet to test write support, but I give read support a “reasonably stable” rating.