12.04hardwareram
I have ubuntu 11 running off a 3.6gb usb flash/stick drive. System has 4gb ram and blank harddisk (wiped using DBAN tool). How do i check if there are no errors in my RAM ? Is there a guaranteed way to check that via some linux command ? If not, it would be great to know why.
Thanks.
Boot with Ubuntu Live CD/USB stick (or press & hold Shift before the splash screen, to enter GRUB menu), and select TEST MEMORY with memtest86+! See this illustration, don't wait for graphical UI!
Illustration:
To test HDD, you can use S.M.A.R.T. data reader, palimpsest disk utility, press Super/Dash button, start typing Disk Utility (for Gnome: System > Administration > Disk utility), and check your S.M.A.R.T. data (YOU MUST UNMOUNT THAT DISK FIRST, YOU WANT TO CHECK ITS FILESYSTEM - that's why, use a Live CD/USB stick - for S.M.A.R.T. reading, the disk could be mounted/used)!
Illustration: 
The best way would be to run through the Ubuntu Friendly Test Suite. Simply search for "Friendly" in the Apps lens, and run the "System Testing" app. This already has all hardware related cases, and is a quick, easy way to test through all hardware enablement test cases. More info can be found here: https://friendly.ubuntu.com/participate/
Best Answer
The Ubuntu Live CD includes a tool called Memtest86+ that will do just that—test your computer’s RAM. Boot up from the Ubuntu LiveCD, press and hold the Shift key, which will bring up the GRUB menu. Select Memory Test