Explanation of Special Permissions
There are three special permissions for files and folders: setuid, setgid, and sticky bit. The setuid and setgid permissions mean that a command is executed as the file owner or group, not as the user or group who ran the command. The sticky bit permission imposes special restrictions on file deletion: only the file owner and root can delete files in the directory.
| Special Permission | Effect on Files | Effect on Directories |
|---|---|---|
| u+s (suid) | The file is executed as the file owner, not as the user who ran it. | No effect |
| g+s (sgid) | The file is executed as the group owner. | Newly created files in the directory inherit the directory’s group. |
| o+t (sticky) | No effect | Users with write permission to the directory can only delete files they own. They cannot delete or modify files owned by others. |
Setting Special Permissions
Symbolic: setuid = u+s; setgid = g+s; sticky = o+t Numeric: setuid = 4; setgid = 2; sticky = 1
Examples
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