Red Hat engineers have been developing Initoverlayfs as a scalable initial file-system. The code is currently in early form and the developers are still looking for feedback from the community as well as figuring out whether it properly belongs in kernel or user-space.

Red Hat is looking at Initoverlayfs as an alternative to Initramfs. Initoverlayfs is to combine the read-only EROFS and Overlayfs to provide an initial file-system that can start "significantly faster" and leverage features like transparent file-system decompression. Red Hat also hopes that Initoverlayfs leads to less fear around initial file-system bloat.

"We implemented the first version of this, by creating a small initramfs that only contains storage drivers, udev and a couple of 100 lines of C code, just enough userspace to mount an erofs with transient overlay. Then we build a second initramfs which has all the contents of a normal everyday initramfs with all the bells and whistles and convert this into an erofs.

Then at boot time you basically transition to this erofs+overlayfs in userspace and everything works as normal as it would in a traditional initramfs."

Those wishing to learn more about the early discussions around Initoverlayfs can see this kernel mailing list thread . Earlier discussions have also taken place on the systemd mailing list .

We'll see where this work on Initoverlayfs leads and if it will ultimately replace initramfs usage on more Linux systems.