SELinux (Security-Enhanced Linux) stands as a crucial security mechanism in Linux distributions, based on policies that provide support for security access control. When working with Docker containers on CentOS 7, SELinux can pose issues regarding access to volume mounts, as it inherently restricts which processes can access files on the host system. This article elucidates how to configure SELinux to permit running Docker containers with custom volume mounts.

Overview of the Procedure

Configuring SELinux to allow Docker containers with custom volume mounts encompasses several steps, including setting appropriate SELinux contexts on shared directories and adjusting SELinux policies for Docker. This guide walks you through the entire process step by step.

Step 1: Checking the SELinux Status

Firstly, it's imperative to ascertain whether SELinux is active. This can be accomplished using the following command:

getenforce

If the command returns Enforcing, SELinux is active and enforcing security policies.

Step 2: Setting SELinux Contexts

To enable access to volume mounts, it's necessary to set the correct SELinux context on directories to be mounted into containers. Utilize the chcon command to set the svirt_sandbox_file_t context, which allows container access:

chcon -Rt svirt_sandbox_file_t /path/to/volume

Replace /path/to/volume with the actual path to the directory you wish to use as a volume.

Step 3: Utilizing SELinux Boolean Rules

SELinux offers boolean variables that enable finer control over access rights. For Docker, relevant ones include:

• docker_can_network
• container_manage_cgroup

To permit running Docker containers with custom volume mounts, it might be necessary to enable the following boolean:

setsebool -P container_manage_cgroup on

 

Step 4: Audit and Troubleshooting

In case of access issues, you can employ the audit2allow tool to analyze audit logs and identify necessary SELinux policy changes. This tool can also generate SELinux modules that you can install to address specific access issues.

 

Configuring SELinux for Docker container management on CentOS 7 requires attention to detail and comprehension of SELinux basic principles. By setting proper contexts and utilizing SELinux boolean variables, you can ensure that your Docker containers can securely access volume mounts. If needed, don't hesitate to leverage audit logs for further troubleshooting and customization of SELinux policies.