File permissions

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chmod

Adminstrators can change file permissions with:

user $chmod [u][g][o] [file]
  • [u] is the number for user permissions
  • [g] is the number for group permissions
  • [o] is the number for other users permissions

Numbers are obtained in the following way:

  • 7 = 4 + 2 + 1 (read/write/execute)
  • 6 = 4 + 2 (read/write)
  • 5 = 4 + 1 (read/execute)
  • 4 = 4 (read)
  • 3 = 2 + 1 (write/execute)
  • 2 = 2 (write)
  • 1 = 1 (execute)

chown

Administrators can change owner and group of a file with:

root #chown [user]:[group] [file]

Administrators can change owner of a folder and files inside recursively with:

root #chown -R [user]:[group] [folder]

gpasswd

Administrators can add a user to a group with:

root #gpasswd -a [user] [group]

Administrators can remove a user from a group with:

root #gpasswd -d [user] [group]