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Systems & Data Center · Advanced

POSIX Access Control List (ACL)

Extended Linux permissions that grant specific users or groups access to a file beyond the single owner, group and others classes.

Definition

ACLs are managed with setfacl and viewed with getfacl; a + at the end of ls -l permissions indicates an ACL is present. A mask entry limits the maximum effective permissions for named users and groups, and default ACLs on directories are inherited by new files.

Example

setfacl -m u:auditor:r /srv/finance/report.csv grants one user read access.

Exam tip

The ACL mask can silently reduce named-user permissions; check the effective rights shown by getfacl.

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