Dracut, dmsquash, and overlays

[Major Hayden]

On Jul 28, 2014, at 10:55, Fabian Deutsch <fabian.deutsch at gmx.de> wrote:

> 
> I am not completely if it is this issue you are seeing, but a squashfs image takes more memory then the image itself, becasue you first need to unsquash (in ram) and the load the fs pages into ram.
> Also take a look here: http://dummdida.tumblr.com/post/89051342705/taking-a-look-at-the-rootfs-footprint-of-a-livecd-and-a
> 
> - fabian

Hello Fabian,

That certainly helps.  I also discovered why the filesystem was filling up so quickly.  I didn't read the docs or the dmsquash-live-root.sh script closely enough.  There's a line where a 512MB snapshot overlay is created if you don't specify your own overlay filesystem[1]

There's another thread from way back in 2009 where the overlay file is discussed along with the lack of a stackable filesystem (AUFS, unionfs, or similar)[2].

Are there any other good options for persistent data for servers booted via live boot?  I'm writing some scripts now that make symlinks from certain directories back to a persistent storage volume on the host.

[1] https://github.com/zfsonlinux/dracut/blob/master/modules.d/90dmsquash-live/dmsquash-live-root.sh#L127
[2] http://fedora.12.x6.nabble.com/Anyone-using-the-overlay-file-td2652964.html

--
Major Hayden