Advanced permissions
This covers the basic permissions for Linux. There are, however, some advanced topics that we'd like to point out, but we will not be discussing them at length. For more information on these topics, check the Further reading section at the end of this chapter. We have included a reference for file attributes, special file permissions, and access control lists.
File attributes
Files can also have attributes that are expressed in another way than the permissions we have seen so far. An example of this is making a file immutable (a fancy word, which means it cannot be changed). An immutable file still has normal ownership and group and RWX permissions, but it will not allow the user to change it, even if it contains the writable permission. Another characteristic of this is that the file cannot be renamed.
Other file attributes include undeletable, append only, and compressed. For more information on file attributes, check the man pages for the lsattr and chattr commands ...
