Quiz Entry - updated: 2026.07.14
What are the three types of users in Linux and their UID ranges?
Root (UID 0), system/service users (1–999), and regular human users (1000–60000) — the kernel only cares about the number; the name in /etc/passwd is for humans.
The UID is what the kernel actually checks for every permission decision; the username is just a label looked up from the number. This is why UID 0 is special no matter what it's called: any account with UID 0 is root. The ranges below are conventions set in /etc/login.defs, not hard kernel rules.
| Type | UID Range | Purpose |
|---|---|---|
| Root | 0 | Superuser with full system access |
| System users | 1-200 (static), 201-999 (dynamic) | Services and daemons |
| Regular users | 1000-60000 | Human users |
Root (UID 0):
- Full system access, no permission checks
- Can read/write/delete any file
- Should only be used when necessary
System users (UID 1-999):
- Run services (apache, mysql, nginx)
- Usually no login shell (
/sbin/nologin) - Created automatically by packages
Regular users (UID 1000+):
- Human users for daily work
- Have home directories in
/home/ - Subject to permission checks
Check your UID:
id # Shows UID, GID, groups
id -u # Just the UID