Kakao DKOS: Analysis of Kubernetes Cgroup Driver and Decision to Retain cgroupfs

The Kakao Cloud Technology Team conducted an in-depth analysis of the role and operational structure of the Cgroup Driver to ensure the stable operation of DKOS, a Kubernetes-based container platform. While official Kubernetes documentation warns that using the cgroupfs Driver with kubelet and Docker in a systemd environment may cause system instability, the actual analysis confirmed that this issue stems from Cgroup management policy conflicts rather than system safety problems.

Cgroup is a Linux feature that isolates resources such as CPU and memory, with two control methods: directly manipulating cgroupfs and using the systemd API. The cgroupfs Driver controls Cgroups by creating file system directories and modifying files, while the systemd Driver manages Cgroups by communicating with systemd via D-Bus. Since both methods ultimately use the Linux Kernel's cgroupfs, there is no difference from the Kernel's perspective.

DKOS decided to continue using the existing cgroupfs Driver for the following reasons:

• Dedicated Node Environment: DKOS's Kubernetes nodes are configured as dedicated VMs/PMs, so conflicts between the cgroupfs Driver and systemd's management policies do not impact actual operations.
• Stability of Direct Control: It was judged that configuring cgroupfs directly is more stable than going through systemd, which is a User Level App.
• Proven Operational Experience: DKOS has used the cgroupfs Driver to date and has not experienced any issues as a result.