when creating a *.iso file, how to make the file size smaller?
 

Hello, is there a way to make a dvd iso file (i already know how to do this part but to make the file size smaller?

yeh, burn as an iso image. the size burned onto the cd is actually smaller than the size of the file

cloop - used by knoppix and other livecd's
squashfs - creates a high compression read-only filesystem(not iso specific)

well the dvd backup i did was 7 gigs... i wouldn't know how to burn it to the dvd..

Maybe you can just bzip2 it(the iso file).

Good suggestion. Sometimes the simple things escape me. ;)

how small does it make it?

It should make it about 25% smaller.

There is absolutely no way to measure that. If your dvd only contains document files or text, then it could possibly shrink it to 1/10th of it's original size. If your dvd contains files that are already zipped in some form, then the bzip2 compression could actually make the dvd larger. You'll just have to try it out.

Also, if you want good compression, but at a faster speed, use gzip. The bzip2 takes about 3 times longer than gzip. (I usually use bzip2 though, because for me space tends to be more valuable.)