Special Permissions
Besides read, write and execute permissions for user, group and others, each file can have three other special permissions which can alter the way a directory works or how a program runs.
| Special Permission | Description |
|---|---|
SetUID or Set User ID--- s on the user permissions --- |
The file that has this permission enable will be executed with the permissions of the user who owns the file. |
SetGID or Set Group ID--- s on the group permissions --- |
This can be applied to executable files or directories. - On executable files, it will grant the process resulting from executing the file access to the privileges of the group who owns the file. - When applied to directories, it will make every file or directory created under it inherit the group from the parent directory. |
Sticky Bit or Restricted deletion flag--- t on the others permissions --- |
This applies only to directories, and on Linux it prevents users from removing or renaming a file in a directory unless they own that file or directory. |