View Full Version : Need help compressing Mac install .app

Jul 29, 2012, 07:59 PM
Hey all,

I have a copy of my Install Mac OS X Lion.app saved on a thumb drive, just in case I ever want to perform a clean install, or access any of the files inside with the handy program Pacifist. However, a 4.2GB file is somewhat burdensome on my USB drive, so I wanted to know if there was a way I could compress the .app to save space. I have used Keka, which is a very nice freeware compress and uncompress utility for OSX, but even when I set the compression setting to maximum, the file only shrinks by about 100MB. I've tried using both 7z and zip formats, but neither seems to work very well.

Is there an app, format, or method that I could use instead that would allow me to compress the install app to a more reasonable size? I could see myself using an archive utility to break the file into multiple .rar archives, but that wouldn't be an optimal solution. Could I put the .app inside of a compressed .img via Disk Utility?

Any suggestions would be most appreciated!

Matthew Yohe
Jul 29, 2012, 08:03 PM
If you have Lion already installed, then you don't need some thumb drive floating around, you have a recovery partition that you can boot from and reinstall Lion from.

Mr. Retrofire
Jul 29, 2012, 08:34 PM
I've tried using both 7z and zip formats, but neither seems to work very well. Any suggestions would be most appreciated!
1. The biggest file (InstallESD.dmg) in the application bundle is a zlib-compressed .dmg-file.
2. The biggest files inside the InstallESD.dmg are already compressed .pkg-files (XAR format) or other compressed .dmg-files like BaseSystem.dmg (invisible).

Could I put the .app inside of a compressed .img via Disk Utility?
The installation app contains already a compressed .dmg-file, InstallESD.dmg under:
/Install OS X Mountain Lion.app/Contents/SharedSupport/

Jul 30, 2012, 05:32 PM
Um, 4GB for the system installer is quite reasonable.

Anything smaller, like breaking it into pieces, would be a waste of time and difficult. How would you reassemble it if your machine is tanked? If this taxes your USB drive you have other problems, so perhaps you'd actually be better off with a bootable Lion installer. Even bigger, but much faster and more versatile.

Aug 2, 2012, 02:01 AM
Thanks for the prompt and helpful replies everyone! Ok, so what I can take away from everyone's comments is:

1.) I can't compress the installer anymore than it already is, since it contains compressed data to begin with.

2.) I can always use the Recovery Partition to reinstall or repair a Lion installation, rather than relying on a disk.

3.) Fragmenting the installer would be difficult because not only does the installer contain compressed content, but it would be difficult to consolidate the separate zip or rar archives in the event of a system failure.

4.) Keeping a dedicated USB drive with the Lion installer on it may be a better solution than lugging it around on a standard data-storage thumb drive.

Ok, so attempting to compress the Lion installer isn't worthwhile, I understand that now. However, I have other, larger files, some 8GB and up, such as .img and .dmg files, and some standard file formats. Is there any compression techniques or programs that anyone here could recommend to shrink them to smaller sizes?