Enabling cgroup v2 on RHEL 8

Enabling cgroup v2 on RHEL 8 for Docker/Podman

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AKSHAY SIV
·

2 min read

Issue

  • Fix container runtime issues when running images with cgroup v2 on a cgroup v1 host.

  • How to enable cgroup v2 on RHEL 8?

  • Is Docker/Podman compatible with cgroup v2 on RHEL 8?

Resolution

By default, RHEL 8 runs on cgroup v1. However, you can switch to using cgroup v2 by adding the systemd.unified_cgroup_hierarchy=1 parameter to the kernel command line and rebooting.

Using the grubby Tool

To modify the kernel command line, use the grubby tool:

# grubby --update-kernel=ALL --args="systemd.unified_cgroup_hierarchy=1"

After applying the change, reboot your system:

# reboot

Verify cgroup v2 Activation

Once the system has rebooted, check whether cgroup v2 is enabled by running:

# mount -l | grep cgroup

Expected output:

cgroup2 on /sys/fs/cgroup type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate)

If you see cgroup2 mounted at /sys/fs/cgroup, cgroup v2 is successfully enabled.

Configuring Docker/Podman to Use cgroup v2

Docker

To ensure Docker runs with cgroup v2, create or modify the Docker daemon configuration file:

# mkdir -p /etc/docker
# echo '{"exec-opts": ["native.cgroupdriver=systemd"]}' > /etc/docker/daemon.json
# systemctl restart docker

Podman

Podman natively supports cgroup v2. Ensure that your system is using the systemd driver:

# echo 'cgroup_manager = "systemd"' >> /etc/containers/containers.conf

Restart any running containers or services using Podman to apply the changes.

Additional Notes

  • Ensure that your container runtime (Docker/Podman) fully supports cgroup v2 before making the switch.

  • Some workloads may require additional configuration adjustments.

  • Use docker info or podman info to verify that cgroup v2 is being used.

By following these steps, you can successfully enable and configure cgroup v2 on RHEL 8 for Docker and Podman.

DockerpodmancgroupsRHEL8