docker change cgroup driver to systemd

Question

I want to docker to start with systemd cgroup driver. for some reason it using only cgroupfs on my centos 7 server.

here is startup config file.

# system         


        

Answer 1

Since I have two configuration file I need to add the entry in the second config file also -- /etc/systemd/system/docker.service.d/docker-thinpool.conf:

--exec-opt native.cgroupdriver=systemd \

Answer 2

Just to add, cgroupfs is dockers own control group manager. However, for the majority of Linux distributions ssytemd is the default init system now and systemd has tight integration with Linux control groups and In Kubernetes site, they recommend using systemd (see below) as using cgroupfs along with systemd seems to be non-optimal

So it is better to use systemd then for cgroup managment. kubelet is configured by default to use systemd. So it is easier and better to change Docker to use the systemd Cgroup driver

A history of this overlap is here https://lwn.net/Articles/676831/

In Kubernetes site, they recommend using systemd https://kubernetes.io/docs/setup/production-environment/container-runtimes/

Cgroup drivers When systemd is chosen as the init system for a Linux distribution, the init process generates and consumes a root control group (cgroup) and acts as a cgroup manager. Systemd has a tight integration with cgroups and will allocate cgroups per process. It’s possible to configure your container runtime and the kubelet to use cgroupfs. Using cgroupfs alongside systemd means that there will then be two different cgroup managers.

Control groups are used to constrain resources that are allocated to processes. A single cgroup manager will simplify the view of what resources are being allocated and will by default have a more consistent view of the available and in-use resources. When we have two managers we end up with two views of those resources. We have seen cases in the field where nodes that are configured to use cgroupfs for the kubelet and Docker, and systemd for the rest of the processes running on the node becomes unstable under resource pressure.

Answer 3

A solution that does not involve editing systemd units or drop-ins would be to create (or edit) the /etc/docker/daemon.json configuration file and to include the following:

{
  "exec-opts": ["native.cgroupdriver=systemd"]
}

After saving it, restart your docker service.

sudo systemctl restart docker

This solution obviously is only feasible if you would want to apply this system-wide.

Answer 4

Try to restart the docker service:

systemctl daemon-reload
systemctl restart docker.service