Access Control Lists provide detailed file permission management by specifying unique access rights for individual users and groups beyond owner, group, others.
Two common commands used to work with ACLs are getfacl and setfactl.
Example
Suppose we want to add permissions for a bob user, who needs to read/write to a specific file, but we do not want to change the general ownership/group/others permission structure. We can use setfacl as follows:
setfact -m u:bob:rw <file>
Note: ACLs don’t replace standard permissions; they extend them,