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Ubuntu Unleashed 2014 Edition: Covering 13.10 and 14.04,Ninth Edition by Paul Hudson, Andrew Hudson, Matthew Helmke

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Altering File Permissions with chmod

You can use the chmod command to alter a file’s permissions. This command uses various forms of command syntax, including octal or a mnemonic form (such as u, g, o, or a and rwx, and so on) to specify a desired change. You can use the chmod command to add, remove, or modify file or directory permissions to protect, hide, or open up access to a file by other users (except for the root account or a user with super user permission and using sudo, either of which can access any file or directory on a Linux system).

The mnemonic forms of chmod’s options are (when used with a plus character, +, to add, or a minus sign, -, to remove):

uAdds or removes user (owner) read, write, or execute permission

gAdds or removes ...

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