ACL masks let you set the maximum allowed permissions for a file on Linux. Find out what they mean, and why they’re so essential.
Are you using Access Control Lists (ACLs) but are confused about the concept of masks? You’re not alone. Let’s dive into this important concept by taking a look at what they are and how they interact with Linux file system permissions.
ACL masks are a way to ensure permissions interoperability with programs and utilities that aren’t ACL-aware.
An ACL mask on a file or directory equates to the maximum permissions allowed to any user or group object that isn’t the owning user, group, or “other” class of the user/group/other class paradigm. To put it another way, it translates ACL entries into POSIX permissions for the sake of backward compatibility.
