很多时候拿到SHELL后有权限拿到/etc/passwd和/etc/shadown文件，这样有一定几率能破解系统帐户！

Debian/Ubuntu

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$ sudo apt-get install john

CentOS/RHEL/Fedora/ReadHat
(Download Link)[http://dag.wieers.com/rpm/packages/john/]

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$ rpm -ivh john*

Crack Passwd

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$ unshadown /etc/passwd /etc/shadown > /tmp/crack.passwd.db

Crack

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$ john /tmp/crack.passwd.db

Show

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$ john -show /tmp/crack.passwd.db