The Sticky Bit

One last special permission bit I want to talk about is the sticky bit.

This permission bit, "sticks a file/directory" this means that only the owner or the root user can delete or modify the file. This is very useful for shared directories. Take a look at the example below:

$ ls -ld /tmp
drwxrwxrwt 6 root root 4096 Dec 15 11:45 /tmp

You'll see a special permission bit at the end here t. Notice it sits where the execute bit for other users would normally be. It means that although anyone may create files in /tmp, you can only delete or rename a file in there if you own it. Without the sticky bit, write permission on a directory would let anybody remove anybody else's files from it, which on a shared directory like /tmp would be a disaster.

Modify sticky bit

$ sudo chmod +t mydir

$ sudo chmod 1755 mydir

The numerical representation for the sticky bit is 1