UID GID

🪪 What Are UID and GID?

✅ UID (User ID)

The User ID is a number that identifies a user on a Unix-like system.

• Each user (like root, alice, bob) has a unique UID.

• The root user always has:

UID = 0

🧠 UID controls what files and actions a process is allowed to access.

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✅ GID (Group ID)

The Group ID is a number that identifies a group of users.

• Each user can be part of one or more groups.

• Each file or process can belong to a group (via GID), and group permissions apply.

🧠 GID controls access rights shared across users in the same group.

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🔧 Example:

Let’s say you have a user named alice:

$ id alice uid=1001(alice) gid=1001(alice) groups=1001(alice),27(sudo)

• UID = 1001 → This is Alice’s identity.

• GID = 1001 → Alice’s main group.

• Groups → Alice is also in the sudo group (which lets her run admin commands).