# Cis GCP Cos 1.3.1

> Ensure authentication required for single user mode

- Skill: `cyberstrikeus/cis-gcp-cos-1-3-1` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-gcp-cos-1-3-1`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-gcp-cos-1-3-1/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-gcp-cos-1-3-1

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# 1.3.1 Ensure authentication required for single user mode (Automated)

## Description

Single user mode (rescue mode) is used for recovery when the system detects an issue during boot or by manual selection from the bootloader.

## Rationale

Requiring authentication in single user mode (rescue mode) prevents an unauthorized user from rebooting the system into single user to gain root privileges without credentials.

## Audit Procedure

Run the following commands and verify that `/sbin/sulogin` or `/usr/sbin/sulogin` is used as shown:

```bash
# grep /systemd-sulogin-shell /usr/lib/systemd/system/rescue.service

ExecStart=-/usr/lib/systemd/systemd-sulogin-shell rescue

# grep /systemd-sulogin-shell /usr/lib/systemd/system/emergency.service

ExecStart=-/usr/lib/systemd/systemd-sulogin-shell emergency
```

## Expected Result

The output should show `ExecStart=-/usr/lib/systemd/systemd-sulogin-shell rescue` for rescue.service and `ExecStart=-/usr/lib/systemd/systemd-sulogin-shell emergency` for emergency.service.

## Remediation

Rootfs is read-only file system. Therefore, update to an OS image which requires single user mode authentication.

## CIS Controls

| Controls Version | Control                                                       | IG 1 | IG 2 | IG 3 |
| ---------------- | ------------------------------------------------------------- | ---- | ---- | ---- |
| v8               | 4.7 Manage Default Accounts on Enterprise Assets and Software | x    | x    | x    |
| v7               | 5.1 Establish Secure Configurations                           | x    | x    | x    |

## Profile

Level 1 - Server | Automated