Several users can write to /srv/dropbox.
Prevent users from freely deleting files owned by other users while preserving ordinary permissions.
Which command is appropriate?
A directory sticky bit restricts deletion and renaming in a shared writable directory to the file owner, directory owner, or a privileged process.
Detailed explanation
chmod +t /srv/dropboxCorrect. chmod +t /srv/dropbox sets the directory sticky bit.
chmod u+s /srv/dropboxIncorrect. u+s sets setuid.
chmod g+s /srv/dropboxIncorrect. g+s sets setgid.
chmod a-x /srv/dropboxIncorrect. Removing execute permission would affect traversal rather than enforce restricted deletion.
Try it yourself
An example you can run in a temporary verification environment.
stat --format=%A /tmpExpected result
一般的なLinuxでは末尾tを含むdrwxrwxrwtKey points
- +t sets sticky bit
- Restricted deletion
- Shared writable directories
Notes
- Environment: GNU coreutils 9.x／Linux
- Command output formatting can vary slightly by distribution or tool version.
- Run the example in a temporary directory or process when possible.
Foundation review
Read the scope first
Check whether the command acts on the current shell, a new process, an existing process, or a file.
Verify the observable result
Use the supplied command and compare the output with the expected result.