(Alternative ZIP method) : If you already have an older functional custom recovery installed, you can download the CWM v6.0.4.5 .zip file directly to your phone's external SD card. Step 2: Boot Galaxy S2 into Download Mode
Ensure you downloaded the .tar version of CWM, not a .zip file meant for custom recoveries.
It provides tools for formatting /system , /data , and /cache partitions, which is often required before a "clean" ROM install. Prerequisites Before You Begin
: Click on the PDA button (or AP button in newer Odin versions) and select the CWM-Recovery-6.0.4.5-i9100.tar file you downloaded.
While the app is a popular tool for installing CWM recovery on many devices, it is highly discouraged for the Galaxy S2 GT-I9100. Many developers on XDA have reported that ROM Manager can cause boot loops or permanent damage to the device due to the S2’s unique partition layout. It is recommended to stick with manual flashing via Odin or recovery.