Baslinux mailing list

[Christian Brandt <brandtc AT psi5.com>]

Ian Scott schrieb:

> One way to do this would be to create a new fs.img, cat /dev/zero into it,
> and cp -a all the contents to it. Then all unused bytes would be zero.
> Send instant messages to your online friends http://uk.messenger.yahoo.com 

 Using something like this should do the trick:

mount fs.img /mnt -o loop
cat /dev/zero >/mnt/zero
rm /mnt/zero
umount /mnt

 But even more effective should be recreating a new image and then 
copying the contents into it again:

 dd if=/dev/zero bs=512 of=fs.img count=howmanyblocks
 mkfs.ext2 -m1 fsnew.img
 mkdir /fsnew /fsold
 mount fsnew.img /fsnew -o loop
 cd /fsold
 tar -cf - | (cd /fsold && tar -xvpf - )
 umount /fsnew /fsold

The later one takes a bit more time but gives also slightly better 
results, that is 2% on a 5MB-file.

Read the manual of mkfs.ext2 as you might need smaller inodes or 
different root-reserves. You might also try ROMFS or minix instead which 
have a little less overhead. But you need a kernel with support for it.

Christian Brandt