Basic information about the characteristics of a user’s account can be found in:

Users and Groups >>> Basic information about the characteristics of a user’s account can be found in: >>> Linux for Developers

 

This is a standard important file

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usermod can add a user to a group.

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sudo is much more controlled than su and has good auditing facilities.

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Yes, this is a correct statement.

su without the dash preserves information

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Without the -c option, echo sudo would not be accessing the root-owned file