# Enable user namespace support

- Source: https://support.icompaas.com/support/solutions/articles/62000234317-enable-user-namespace-support
- Section: [Solutions](https://support.icompaas.com/support/solutions) › [CIS Docker Benchmark v1.7.0](https://support.icompaas.com/support/solutions/62000112687) › [CIS Docker Benchmark](https://support.icompaas.com/support/solutions/folders/62000169241)
- Last updated: 2026-05-29
- Publisher: iCompaas, Inc. (https://www.icompaas.com)

**Profile Applicability:**

-   **Level 2** 
    

**Description:**

User namespace support should be enabled in the Docker daemon to utilize container user-to-host user remapping. This configuration provides an additional security layer by isolating container users from host system users.  

**Rationale:**

Enabling user namespaces in Docker allows containers to have their own range of user and group IDs (UID/GID), separate from those used by the host system. This enhances security by ensuring that the root user inside the container is mapped to a non-privileged user on the host system.  

**Impact:**

**Pros:**  

-   Provides better security by mapping the container's root user to a non-root user on the host.  
    
-   Limits the potential for privilege escalation attacks between containers and the host system.  
    

**Cons:**  

-   User namespace remapping is still in its early stages and may cause issues or difficulty in configuring some container images, especially if they rely on specific user IDs.  
    

**Default Value:**

-   By default, user namespaces are not enabled in Docker. Docker containers typically share the user namespaces with the host unless configured otherwise.  
    

**Pre-requisites:**

-   Administrative access to the Docker host system.  
    
-   Docker daemon must be restarted to apply changes.  
    

**Remediation**

**Test Plan:**

**Using AWS Console:**

1.  Log in to the EC2 instance running Docker.  
    
2.  Check if user namespace support is enabled by running the following command:  
    
    docker info --format '{{ .SecurityOptions }}'
    
      
    
3.  Using AWS CLI:
    
4.  Connect to the EC2 instance where Docker is running.  
    
5.  Run the following command to check for user namespace support:  
    
    docker info --format '{{ .SecurityOptions }}'
    
      
    

**Implementation Plan:**

**Using AWS Console:**

1.  Log in to the EC2 instance.  
    
2.  Ensure that the /etc/subuid and /etc/subgid files exist. If they do not, create them:
    
    touch /etc/subuid /etc/subgid
    
3.  Modify the Docker daemon configuration file /etc/docker/daemon.json to enable user namespace remapping:
    
    {
      "userns-remap": "default"
    }
    
4.  Restart Docker to apply the configuration:  
    
    sudo systemctl restart docker
    

**Using AWS CLI:**

1.  Use SSM to ensure the /etc/subuid and /etc/subgid files exist and apply the user namespace remapping:
    
    aws ssm send-command --document-name "AWS-RunShellScript" --targets "Key=instanceIds,Values=instance\_id" --parameters 'commands=\["touch /etc/subuid /etc/subgid && echo \\'{\\"userns-remap\\": \\"default\\"}\\' > /etc/docker/daemon.json && sudo systemctl restart docker"\]'
    
      
    

**Backout Plan:**

1.  Using AWS Console:
    
2.  Log in to the EC2 instance.  
    
3.  Revert the Docker configuration by disabling user namespace remapping in /etc/docker/daemon.json:  
    
4.  {
      "userns-remap": "default"
    }
    
5.  Restart Docker:  
    
    sudo systemctl restart docker
    
      
    

**Using AWS CLI:**

1.  Use SSM to disable user namespace remapping and restart Docker:  
    
    aws ssm send-command --document-name "AWS-RunShellScript" --targets "Key=instanceIds,Values=instance\_id" --parameters 'commands=\["echo \\'{\\"userns-remap\\": \\"default\\"}\\' > /etc/docker/daemon.json && sudo systemctl restart docker"\]'
    
      
    

**References:**

-   CIS Docker Benchmark v1.7
    
-   Docker Documentation on User Namespace: [https://docs.docker.com/engine/security/userns-remap/](https://docs.docker.com/engine/security/userns-remap/)[  
      
    ](https://docs.docker.com/engine/security/userns-remap/)

## Related compliance guidance

- [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Configuration checks like this one are the technical half of a SOC 2 / ISO 27001 programme — the guide shows where they fit, what else an auditor expects, and how to evidence them.
- [ISO/IEC 27001:2022 compliance: a practical implementation guide](https://support.icompaas.com/compliance/iso-27001-2022): ISO 27001 Annex A.8 (technological controls) is where cloud hardening evidence lands; the guide shows how to run the ISMS around it.