By now you would have come across the upgrade procedure for getting Mac OS X Lion 10.7. Apple relies on a cloud based software distribution on new version. This kind of installation process is a bit displeasing for people those who have throttled broadband bandwidth and slow internet connections. They evidently need an offline Lion installer available on DVD or USB disk.
Mac OS X 10.7 Lion installer comes with an extension .app. You can copy this setup file to a DVD disc or external storage device after downloading it from the Mac store. Inside the Lion app folder there is a DMG file which can be mounted on suitable medium. And it supports re-installation of the OS in offline mode without an internet connection. Interested? Here is how to do that.
Buy Lion from Mac Store. Copy the installer to safe storage media and find InstallESB.dmg from Contents> SharedSupport folder. Run this disc image whenever you want to re-install Lion from Snow Leopard 10.6.8.
Creating offline Lion installer bootable from USB disk: It requires a USB disk with more than 4GB of storage and a freeware Mac OS app called Carbon Copy Cloner. Search Google to find download link.
Open Mac Disc Utility and Erase the USB drive in Mac OS Extended (Journaled) format. Run Carbon Copy Cloner.
Choose the option-Restore from Disk Image as Source Disk input for the app. Then locate and mount InstallESB.dmg file. Now point our USB drive to Target Disk on the right side. Carbon Copy Cloner will clone a copy of the Lion installer to the disk.
On restart, press option key for a few seconds. You will notice a USB disk listed with other boot choices. Select it and in the next step click on Re-install Mac OS X Lion and proceed.