Traditional UNIX/Linux divided everyone on Earth into three groups:
- The owner of the file. This is usually the file creator.
- The team of the owner. This is usually other members on the same project so they can share files easily.
- Everyone else who can get access to the system.
As UNIX/Linux moved to larger platforms, and gained a larger user complement, the original groupings did not allow enough flexibility to manage users, auditors, developers, production streams, and on all the rest. ACL is a bolt-on accessory used to implement this fine level of resource control.
ACLs have been around for a long, long time; I first encountered ACLs way back in the late 70’s and they show up everywhere. Must have been a good idea.