Well I have installed avast anti virus on Ubuntu 12.04. But after updating, it crashes! So I have made some tweaks like below: Press Ctrl+Alt+T to open the Terminal. When it opens, run the command below. sudo gedit /etc/init.d/rcS Type your password and hit Enter. When the text file opens, add the line: sysctl -w kernel.shmmax=128000000 Make sure the line you added is before: exec /etc/init.d/rc S This is what it should look like: #! /bin/sh # rcS # # Call all S??* scripts in /etc/rcS.d/ in numerical/alphabetical order # sysctl -w kernel.shmmax=128000000 exec /etc/init.d/rc S Save the file. Reboot. My question is: Did I do anything wrong? I mean as I have made some tweaks, will it lower the security of Avast down like viruses do? Please if you are a programmer check this if it contains bug or harmful intentions... Thanks.