8MB limit on genext2fs?

[Dan Kegel]

Back in April, I wrote:
> Thanks to Larry Doolittle, who pointed me to
> http://recycle.lbl.gov/~ldoolitt/bse/
> and genext2fs as a way to generate initrd images without root.
>
> It has a limit of 8MB or so
> (see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=122729 )
> This is a problem for embedded systems with big fat C++ apps.
>
> The code says:
> // I don't do triple indirect - it's such a small filesystem ...
> else
> errexit("file too big ! blocks list for inode %d extends past
> double indirect blocks!", nod);
>
> Has anyone implemented triple indirect in genext2fs yet?
> Or should I give it a shot?

Vasan Sundar implemented this while interning at Ixia Communications,
and we've been happily using it to generate 9 MB filesystems.
Hopefully the maintainer will pick up these patches, but in the
meantime, they're at
http://home.attbi.com/~vr_sundar/genext2fs.html

- Dan

[Grant Taylor]

Dan Kegel <da...@kegel.com> writes:

> Vasan Sundar implemented this while interning at Ixia Communications,
> and we've been happily using it to generate 9 MB filesystems.

> http://home.attbi.com/~vr_sundar/genext2fs.html

We routinely construct 200MB+ ramdisk images as a nonroot user, but
using a different trick.

The standard "tune2fs" program and libext2fs contain almost everything
necessary to write arbitrary stuff into a filesystem in a file. I
wrote a tune2fs script generator that took a filetree and output a set
of commands to replicate the tree using tune2fs.

Alas, it is not mine to post, but the script was exceptionally easy to
write. I ended up whacking tune2fs to exit(1) on error, added one
extra feature (chmod? long name symlinks? somesuch) and we were in
business.

--
Grant Taylor - gtaylor<at>picante.com - http://www.picante.com/~gtaylor/
Linux Printing Website and HOWTO: http://www.linuxprinting.org/