[lug] Max file size

[John Karns]

On Tue, 18 Dec 2001, Sean Reifschneider said:

> On Tue, Dec 18, 2001 at 01:53:02PM -0500, John Karns wrote:
> >I would like to use dd to create a compressed image file of a vfat
> >partition which exceeds 2GB in size, and I bump into the limit which
>
> Well, first of all you can use compression to bring the size down:
>
>    dd if=/dev/hdaN | bzip2 >hdaN.dd.bz2

I had tried compression, although with gzip.  The sectors in the free
space area of the vfat partition must have contained highly randomized
data; it didn't compress well at all.


> Another thing that can help is to mount the DOS partition and then do "dd
> if=/dev/zero of=/mnt/dosdrive/zero; rm /mnt/dosdrive/zero".  This fills up
> the partition with zeros, so that it compresses better.

This was a nice trick, and did indeed seem to make a difference.
Although I also had to use the split mechanism for that as well, despite
using a version of dd recompiled to handle large files.  Thus it appears
that the vfat handling in the 2.2.20 kernel is also limited to 2GB file
sizes ... or maybe there's something other factor involved.


> On my laptop, running KRUD 7.2, it seems to work fine with dd:
>
>    [2] guin:jafo# dd if=/dev/zero of=bigfile
>    <Control-C after a while>
>    [2] guin:jafo# ls -l bigfile
>    -rw-r--r--    1 root     root         2.9G Dec 18 18:01 bigfile

Out of curiosity, is that with ext2fs?

----------------------------------------------------------------
John Karns                                        jkarns at csd.net