# Cis Ubuntu2004 V300 1 1 1 2

> Ensure freevxfs kernel module is not available

- Skill: `cyberstrikeus/cis-ubuntu2004-v300-1-1-1-2` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu2004-v300-1-1-1-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu2004-v300-1-1-1-2/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-ubuntu2004-v300-1-1-1-2

---


# Ensure freevxfs kernel module is not available

## Profile

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

## Description

The `freevxfs` filesystem type is a free version of the Veritas type filesystem. This is the primary filesystem type for HP-UX operating systems.

## Rationale

Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it.

## Audit Procedure

### Command Line

Verify the `freevxfs` kernel module is not available on the system - OR - has been disabled.

Run the following script to determine if the `freevxfs` kernel module is available on the system:

```bash
#!/usr/bin/env bash

{
   l_mod_name="freevxfs" l_mod_type="fs"
   while IFS= read -r l_mod_path; do
      if [ -d "$l_mod_path/${l_mod_name}/-/\/" ] &&  [ -n "$(ls -A "$l_mod_path/${l_mod_name}/-/\/")" ]; then
         printf '%s\n' "$l_mod_name exists in $l_mod_path"
      fi
   done < <(readlink -f /usr/lib/modules/**/kernel/$l_mod_type || readlink -f /lib/modules/**/kernel/$l_mod_type)
}
```

If nothing is returned, the `freevxfs` kernel module is not available on the system and no further audit steps are required.

Note: Some systems may include the `freevxfs` filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state.

If anything is returned, verify the `freevxfs` kernel module is not loaded and not loadable by performing the following:

Run the following command to verify the `freevxfs` kernel module is not loaded:

```bash
# lsmod | grep 'freevxfs'
```

Nothing should be returned

Run the following command to verify the `freevxfs` kernel module is not loadable:

```bash
# modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+freevxfs\b'
```

Verify the output includes:

```
blacklist freevxfs
 -AND-
install freevxfs /bin/false
 -OR-
install freevxfs /bin/true
```

## Expected Result

```
blacklist freevxfs
install freevxfs /bin/false
```

## Remediation

### Command Line

Run the following to unload and disable the `freevxfs` kernel module:

```bash
# modprobe -r freevxfs 2>/dev/null
# rmmod freevxfs 2>/dev/null
```

Perform the following to disable the `freevxfs` kernel module:

Create a file ending in `.conf` with `install freevxfs /bin/false` in the `/etc/modprobe.d/` directory

Example:

```bash
# printf '\n%s\n' "install freevxfs /bin/false" >> freevxfs.conf
```

Create a file ending in `.conf` with `blacklist freevxfs` in the `/etc/modprobe.d/` directory

Example:

```bash
# printf '\n%s\n' "blacklist freevxfs" >> freevxfs.conf
```

## Default Value

Not disabled by default.

## References

1. NIST SP 800-53: CM-7 a
2. NIST SP 800-53A: CM-7.1 (ii)

## CIS Controls

v8 - 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software (IG 2, IG 3)
v7 - 9.2 Ensure Only Approved Ports, Protocols and Services Are Running (IG 2, IG 3)

MITRE ATT&CK Mappings: T1005, T1005.000 | TA0005 | M1050