i'm new user in Back Track 5 but i don't know commands for Back Track 5. where can i study ?

Go to the BT Linux site. This is a distribution intended for security professionals who need to do sophisticated system/network penetration testing. If that is your intended goal, then great! If not, then you should try another, more user friendly, distribution, such as Ubuntu, Mint, etc.

Anyway, here is a link to the BT web site: http://www.backtrack-linux.org/
They have tutorials, FAQs, user forums, and other helpful tools.

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