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su is a utility to run a shell or other command as another user (root by default).

su is a utility that runs a shell or a specified command as another user. By default, the other user is root, and su, with , is one of the two common ways of obtaining administrator privileges. Calling su usually requires typing the target user's password.

su originally stood for “super user” (it was only for running a root shell), and became later known as “substitute user” (or “switch user” or a number of similar backronyms) when it started accepting the target user name as an argument.

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