# Cis Ubuntu1604 V200 1 1 4

> Ensure nosuid option set on /tmp partition

- Skill: `cyberstrikeus/cis-ubuntu1604-v200-1-1-4` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1604-v200-1-1-4`
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- 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-ubuntu1604-v200-1-1-4

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# Ensure nosuid option set on /tmp partition

## 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

```bash
# If a /tmp partition exists, verify that the nosuid option is set
# Run the following command and verify that nothing is returned:
findmnt -n /tmp | grep -v nosuid
```

## Expected Result

No output should be returned.

## Remediation

### Command Line

```bash
# Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /tmp partition.
# See the fstab(5) manual page for more information.
# Run the following command to remount /tmp:
mount -o remount,nosuid /tmp

# OR Edit /etc/systemd/system/local-fs.target.wants/tmp.mount to add nosuid to the /tmp mount options:
# [Mount]
# Options=mode=1777,strictatime,noexec,nodev,nosuid

# Run the following command to remount /tmp:
mount -o remount,nosuid /tmp
```

## Default Value

Not set by default.

## References

- CIS Controls Version 7 - 5.1 Establish Secure Configurations: Maintain documented, standard security configuration standards for all authorized operating systems and software.

## Profile

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