Re: Large ramdisks, kernel memory space issue

[Goswin von Brederlow <brederlo@informatik.uni-tuebingen.de>]

salman h <salman_debian@yahoo.com> writes:

> Anyway, another user suggested a feasible sounding
> solution:
> Make the initrd small enough to fit in low mem.
> Mount more ramdisks later during the init process
> (either by downloading from the server, or from the CD
> if using ISOLinux, etc).
>
> I hope that makes sense.
>
> Thanks for your help.
>
> Salman

If you have a CD/DVD then place the filesystem in a file there. On
boot setup a loop device (or cloop for more space) for that file and a
second loop device on a sparse file in tmpfs (or use a ramdisk
ramdisk). Then setup the tmpfs loop device as copy-on-write storage
device for the first loop device (same config lvm snapshots use) with
dmsetup.

Now you have a writeable block device that starts of being completly
on cdrom and stores any changes in tmpfs. Much more memory efficient
and faster to boot too.

But beware, if you have too many changes and the COW device gets full
bad things tend to happen. Make it big enough / have enough ram.

MfG
        Goswin