Absinthe is multiplatform iOS5 JailBreak tool which can easily be used on iPhone 4S and iPad2. Absinthe have a linux version too. Jailbreaking is the process of modifying the iOS Kernel which enables you to install apps from sources other than Apple AppStore. You will need libimobildevice from its PPA or through following commands
sudo add-apt-repository ppa:pmcenery/ppa sudo apt-get update sudo apt-get install libimobiledevice-utils
If you have trouble installing through above instructions than you can always look libimobiledevice.org
Now download Asinthe 0.3 from following link
After download look for absinthe.x86 if you are on x86 Linux distribution and look for absinthe.x86_64 if you are on 64bit operating system.
After opening your required file a window of Absinthe will pop up, than just follow on screen instructions to jailbreak your device.