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Linux Intermediate

What is ACL (Access Control List)?

An extension to standard Linux file permissions that allows setting fine-grained access rights for specific users and groups beyond owner/group/other.

Standard Unix permissions only allow three access levels: owner, group, and others. ACLs extend this by letting administrators grant permissions to any number of specific users or groups on a single file. For example, user alice can have read-write access while user bob gets read-only, without changing file ownership or group. Commands include getfacl (view ACLs), setfacl -m u:alice:rw file (set ACL), and setfacl -x u:alice file (remove ACL). Default ACLs on directories automatically apply to new files created within. ACLs require filesystem support (enabled in ext4, XFS by default).

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