# Cis Ubuntu1804 V220 4 5 3

> Ensure default group for the root account is GID 0

- Skill: `cyberstrikeus/cis-ubuntu1804-v220-4-5-3` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1804-v220-4-5-3`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu1804-v220-4-5-3/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-ubuntu1804-v220-4-5-3

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# CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 4.5.3

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Description

The `usermod` command can be used to specify which group the root user belongs to. This affects permissions of files that are created by the root user.

## Rationale

Using GID 0 for the `root` account helps prevent `root`-owned files from accidentally becoming accessible to non-privileged users.

## Audit Procedure

### Command Line

Run the following command and verify the result is `0`:

```bash
grep "^root:" /etc/passwd | cut -f4 -d:
```

### Expected Result

```
0
```

## Remediation

### Command Line

Run the following command to set the `root` user default group to GID `0`:

```bash
usermod -g 0 root
```

## References

1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5

## CIS Controls

v8 - 3.3 Configure Data Access Control Lists - Configure data access control lists based on a user's need to know.

v7 - 14.6 Protect Information through Access Control Lists.

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Assessment Status

Automated