Linux Permissions
Linux Permissions
Linux Special Permissions: sticky bit
NB: This tutorial has worked on Centos 6,7,8 and 9
The sticky bit, when set on a directory, is a special permission that has different effects depending on the user's relationship to the directory. This permission is primarily used on directories where multiple users have write access, such as the /tmp directory. When the sticky bit is set on a directory, only the owner of a file within that directory can delete or rename the file, even if other users have write permissions in that directory. This is often used to secure the /tmp directory, ensuring that users can only delete their own files.
| Special Permission | Letter Representation | Numerical (Octal) Representation | Types of files it works on |
|---|---|---|---|
| sticky bit | t | 1 | folders only |
Examples of sticky bit using letter representation
We can enable the sticky bit by using “o+t”. In this example, I enable it on the folder named “example” by running the command “chmod o+t example”. When we do a long listing using “ls -l”, we see that the letter “t” has been added to the “others” section of the permissions. This shows that the bit is enabled on the directory.
We can remove the sticky bit by running “o-t”. In this example, I have run the command “chmod o-t example” where example is the name of the folder. When we list using “ls -l”, we see that the letter “t” has been removed from the “others” section of the permissions. This shows that the bit had been removed.
Examples of sticky bit using numbers (octal) representation
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We can use the number “1” to add the sticky bit to a directory. The “1” is added in front of the 3 standard permissions. As seen in this figure, I run the command “chmod 1755 example”. The leftmost “1” is the sticky bit, followed by 3 standard permissions. When we do a long listing “ls -l”, we see that the letter “t” is in the “others” section of the permissions showing that the bit is enabled.
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We can then remove the sticky bit by using zero “0” in front of the standard permisions. In this case I ran “chmod 0755 example” to remove the sticky bit from the “example” folder. When we do the listing using “ls -l”, we see that the letter “t” is removed, meaning that the sticky bit is disabled on the folder.