Overlayfs for 3.10 [LWN.net]

By Jonathan Corbet
March 13, 2013

The "overlayfs" filesystem is one implementation of the union filesystem concept, whereby two or more filesystems can be combined into a single, virtual tree. LWN first reported on overlayfs in 2010; since then it has seen continued development and has been shipped by a number of distributors. It has not, however, managed to find its way into the mainline kernel.

In a recent posting of the overlayfs patch set, developer Miklos Szeredi asked if it could be considered for inclusion in the 3.10 development cycle. He has made such requests before, but, this time, Linus answered:

Yes, I think we should just do it. It's in use, it's pretty small, and the other alternatives are worse. Let's just plan on getting this thing done with.

At Linus's request, Al Viro has agreed to review the patches again, though he noted that he has not been entirely happy with them in the past. Unless something serious and unfixable emerges from that review, it looks like overlayfs is finally on track for merging into the mainline kernel.

Index entries for this article
Kernel	Filesystems/Union
Kernel	Overlayfs

to post comments

Overlayfs for 3.10

Posted Mar 14, 2013 12:37 UTC (Thu) by giggls (subscriber, #48434) [Link] (1 responses)

One of the typical deployment scenarios for a union type filesystem (actually the one I currently use aufs for) is diskless clients where /etc is made from 2-3 components:
global(ro), client-specific(rw via NFS), local (optional, rw on ramdisk)

AFAIR this can not be done in overlayfs. So this is going to be worthless for the diskless crowd right?

Sven

Overlayfs for 3.10

Posted Mar 21, 2013 2:08 UTC (Thu) by i3839 (guest, #31386) [Link]

I don't know about overlayfs, but considering /etc/ is tiny you could achieve the same result by copying the global components to a local ramdisk/tmpfs and mount-bind the client-specific NFS files/directories one by one with a script. If you don't need local rw, just bind directly on top of the global fs. Or do it the other way round, bind the global fs components on top of the NFS, whatever is more convenient.

Overlayfs for 3.10

Posted Mar 21, 2013 5:37 UTC (Thu) by heijo (guest, #88363) [Link]

Nice, how do we register for the celebrations?