What is the purpose of the sticky bit in Linux?

The sticky bit is a permission setting that is primarily used on directories in Linux. Its main purpose is to restrict deletion privileges within that directory. When the sticky bit is set on a directory, only the file's owner or the root user can delete or rename the files located within it. This is particularly useful in shared directories, such as /tmp, where multiple users can create files but should not have the ability to delete each other's files.

By using the sticky bit, system administrators can enhance security and avoid accidental or malicious deletions of files by users who do not own them. This helps maintain order and security in a multi-user environment, where users need to work collaboratively without compromising each other’s data.

The other options refer to different aspects of file permissions or execution. For instance, preventing file permissions from changing refers more to immutable attributes, ensuring execution of a file relates to the executable permission without the specific functionality of the sticky bit, and allowing unrestricted access contrasts with what the sticky bit actually does, which is to impose restrictions on file management within a directory.