Episode 36 — Users, groups, and identity: UID, GID, EUID, EGID explained simply
Linux+ tests identity concepts because permissions, auditing, and service behavior all depend on which identity the system believes is acting. This episode explains UID and GID as the core numeric identities for users and groups, then clarifies the “effective” identities—EUID and EGID—that determine what access checks actually use at runtime. You’ll learn why the exam emphasizes numbers, not names: names are labels, but UIDs and GIDs are the real keys stored on files and evaluated by the kernel. Understanding the difference between real and effective identity helps you interpret common scenarios like a process that can access a resource only when run a certain way, or a command that behaves differently under sudo, setuid programs, or service accounts.
we connect identity theory to practical troubleshooting and least-privilege design. You’ll practice reasoning through cases where file ownership looks correct but access is still denied because the effective group membership is not what you think, or where a service fails because it runs under a restricted account without needed permissions. We also cover best practices: assign groups based on functional access, avoid broad shared accounts, and treat changes to UID/GID assignments as high-impact because they can orphan files or break applications that expect stable identities. Finally, you’ll learn an exam-ready verification mindset: confirm the running identity, confirm group memberships as they are actually applied to the session or process, and confirm file and directory permissions in the path, not just the final target. Produced by BareMetalCyber.com, where you’ll find more cyber audio courses, books, and information to strengthen your educational path. Also, if you want to stay up to date with the latest news, visit DailyCyber.News for a newsletter you can use, and a daily podcast you can commute with.
