LarsBlog

I've seen some benchmarks recently showing just how much smaller 7z compression can be than traditional zip/gzip/bzip.  This motivated me to update some regular archiving scripts to switch from gzip compression to 7z.

Normally to create a compressed tar archive under Linux, you do something like this:

tar cvzf <Destination archive>.tar.gz <source folder>

To use 7z instead, you first need to make sure it's installed - which on Ubuntu/Debian based systems you can do as follows:

sudo apt-get install p7zip p7zip-full

Then you can pipe your tar output through 7z:

tar cf - <source folder> | 7z a -mx=9 -si <Destination archive>.tar.7z

It really works!  Some of my text-heavy directories were 40% smaller using 7z "Ultra" compression.

The above command uses the following parameters.

tar:
cf -> create archive
- -> output to stdout instead of a file

7z:
a -> Add to archive
-mx=9 -> Use "ultra" compression (slower but smaller)
-si -> Read from stdin instead of from a file/folder.

On unix filesystems, it's recommended to use tar and 7z in combination in this way because 7z by itself will not preserve file permissions and ownership.