Historically, configuring the correct cgroup driver has been a pain point for users running new
Kubernetes clusters. On Linux systems, there are two different cgroup drivers:
cgroupfs and systemd. In the past, both the kubelet
and CRI implementation (like CRI-O or containerd) needed to be configured to use
the same cgroup driver, or else the kubelet would exit with an error. This was a
source of headaches for many cluster admins. However, there is light at the end of the tunnel!
Automated cgroup driver detection
In v1.28.0, the SIG Node community introduced the feature gate
KubeletCgroupDriverFromCRI, which instructs the kubelet to ask the CRI
implementation which cgroup driver to use. A few minor releases of Kubernetes
happened whilst we waited for support to land in the major two CRI implementations
(containerd and CRI-O), but as of v1.31.0, this feature is now beta!
In addition to setting the feature gate, a cluster admin needs to ensure their
CRI implementation is new enough:
- containerd: Support was added in v2.0.0
- CRI-O: Support was added in v1.28.0
Then, they should ensure their CRI implementation is configured to the
cgroup_driver they would like to use.
Future work
Eventually, support for the kubelet’s cgroupDriver configuration field will be
dropped, and the kubelet will fail to start if the CRI implementation isn’t new
enough to have support for this feature.