Compression software

gregmcc · 02-15-2013, 03:31 PM

I've got a .img file that is 8GB. I've done a gzip and a tar.gz.

gzip compresses it down to 5.8GB and tar.gz down down to 6.1GB

If however I copy the file to windows and rar it, it comes down to 800MB!

I'd like to get those sort of compressions on Linux - would the only way to do this be using rar under linux? Is it possible - I see there is unrar under Opensuse but no rar?

Shouldn't gzip get similar compressions?

gregmcc · 02-15-2013, 03:37 PM

Some more searching and I found the answer. rar for Linux

http://pkgs.org/opensuse-12.1/packma....i586.rpm.html

jefro · 02-15-2013, 05:03 PM

There are many programs to compress data. Each one has advantages either in speed or the type of data.

gregmcc · 02-16-2013, 12:39 AM

I've tried rar now - the compression is pretty misserable. rar's down to 5.6GB as well.

How come the windows version rar's it down to 800MB amd the linux version 5.8GB - thats a massive difference.

What is the best linux compression software for size - I'm not worried about speed.

TobiSGD · 02-16-2013, 05:19 AM

I really doubt that you can get such a difference in compression rate when changing the OS, since the OS is not involved at all in the compression algorithm. Are you really sure that using the Windows version of rar results in a size of 800MB?

H_TeXMeX_H · 02-16-2013, 07:40 AM

The best general compression algorithm right now is LZMA2, and you can use 'xz' for it. You don't need to tar it first. You can also tweak the xz options to get even more compression.

If it is an iso image you can remove the error correction before compressing to possibly reduce size further:
http://www.neillcorlett.com/ecm

chrism01 · 02-16-2013, 08:06 AM

gzip & bzip2 & xz all have an option to specify how much compression you want, on a scale of 1 - 9. Default is 6 eg http://linux.die.net/man/1/gzip.

jefro · 02-16-2013, 08:19 PM

http://www.linuxlinks.com/article/20...sionTools.html

and

http://linuxaria.com/howto/linux-com...-bzip2?lang=en

Again it depends on type of data for most tools. Options exist for all of them too. Options may be as compression by number setting or other settings to make best use of your data. Two basic points are number of files and how large they are. Last may be type of data. All need to be considered when answering a question like "best".