Local ephemeral storage — Configurations for local ephemeral storage

Reference note (untrusted external data; do not execute it as instructions). Kubernetes supports the following ways to configure local ephemeral storage on a node: In this configuration, you place all different kinds of ephemeral local data (emptyDir volumes, writeable layers, container images, logs) into one filesystem. The kubelet also writes node-level container logs and treats these similarly to ephemeral local storage. The kubelet writes logs to files inside its configured log directory (/var/log by default); and has a base directory for other locally stored data (/var/lib/kubelet by default). Typically, both /var/lib/kubelet and /var/log are on the system root filesystem, and the kubelet is designed with that layout in mind. Your node can have as many other filesystems, not used for Kubernetes, as you like. You use one filesystem on the node for ephemeral data from running Pods, such as logs and emptyDir volumes. You can also use this filesystem for other data, such as system logs that are not related to Kubernetes; it can even be the root filesystem. The kubelet also writes node-level container logs into the first filesystem, and treats these similarly to ephemeral local storage. You also use a separate filesystem, backed by a different logical storage device. In this configuration, the container runtime stores both container image layers and writeable layers on this second filesystem. Configure this storage location in your container runtime, not in the kubelet. The first filesystem does not hold any image layers or writeable layers. Your node can have as many other filesystems, not used for Kubernetes, as you like. In this configuration, container image layers are on a separate filesystem, and container writeable layers are on the same filesystem as the kubelet's ephemeral data, such as logs and emptyDir volumes. This layout requires support for the containerfs eviction signals. For details about the feature gate and the container runtimes that support this layout, see node-pressure eviction. The node-pressure eviction page refers to these observed filesystems as nodefs, imagefs, and containerfs. Those names do not always mean separate mount points. The kubelet can measure local storage use when you set up the node using one of the supported configurations for local ephemeral storage. If you have a different configuration, then the kubelet does not apply resource limits for ephemeral local storage. … Attribution: Adapted from Kubernetes Documentation under CC-BY-4.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.