# Cis Ubuntu1804 V220 1 1 2 4

> Ensure nosuid option set on /tmp partition

- Skill: `cyberstrikeus/cis-ubuntu1804-v220-1-1-2-4` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1804-v220-1-1-2-4`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu1804-v220-1-1-2-4/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-v220-1-1-2-4

---


# Ensure nosuid option set on /tmp partition

## Profile

Level 1 - Server / Level 1 - Workstation, Assessment: Automated

## Description

The nosuid mount option specifies that the filesystem cannot contain setuid files.

## Rationale

Since the /tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /tmp.

## Impact

None noted.

## Audit Procedure

### Command Line

Verify that the nosuid option is set for the /tmp mount.

```bash
# findmnt -kn /tmp | grep nosuid
```

## Expected Result

```
/tmp     tmpfs  tmpfs   rw,nosuid,nodev,noexec,relatime,seclabel
```

## Remediation

### Command Line

Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /tmp partition.

```bash
# Example:
# <device> /tmp   <fstype>   defaults,rw,nosuid,nodev,noexec,relatime   0 0

# Run the following command to remount /tmp with the configured options:
mount -o remount /tmp
```

## Default Value

Not set by default.

## References

1. See the fstab(5) manual page for more information.
2. NIST SP 800-53 Rev. 5: AC-3, MP-2

## CIS Controls

v8 - 3.3 Configure Data Access Control Lists (IG 1, IG 2, IG 3)
v7 - 14.6 Protect Information through Access Control Lists (IG 1, IG 2, IG 3)

MITRE ATT&CK Mappings: T1548, T1548.001 (TA0005) - M1022, M1038