In the rapidly evolving landscape of cloud-native development and container orchestration, the underlying infrastructure often becomes an opaque black box. For developers and system administrators working with Kubernetes, containerd, or CRI-O, one acronym repeatedly surfaces when debugging storage issues: CRI .
"lowerdir": "/var/lib/containerd/io.containerd.snapshotter.v1.overlayfs/snapshots/12/fs:/var/lib/containerd/io.containerd.snapshotter.v1.overlayfs/snapshots/11/fs", "upperdir": "/var/lib/containerd/io.containerd.snapshotter.v1.overlayfs/snapshots/23/fs", "workdir": "/var/lib/containerd/io.containerd.snapshotter.v1.overlayfs/snapshots/23/work" The upperdir is where all write changes to the container are stored. Go there: cri file system tools install
But what exactly are "CRI file system tools," and why would you need to install them? This comprehensive guide will demystify the CRI (Container Runtime Interface) filesystem utilities, walk you through every installation method, and show you how to leverage these tools to inspect, debug, and optimize your container storage layers. Before diving into installation, we must clarify a common misconception. Unlike ext4 or NTFS tools, "CRI file system tools" refer to a suite of command-line utilities specifically designed to interact with the storage plugins and fileystem namespaces created by CRI-compliant runtimes (containerd, CRI-O). Go there: But what exactly are "CRI file
sudo du -sh /var/lib/containerd/io.containerd.snapshotter.v1.overlayfs/snapshots/*/fs | sort -h The largest directory is the culprit. With nerdctl , you can bypass low-level snapshot IDs: Unlike ext4 or NTFS tools, "CRI file system
VERSION="v1.30.0" curl -L https://github.com/kubernetes-sigs/cri-tools/releases/download/$VERSION/crictl-$VERSION-linux-amd64.tar.gz | sudo tar -xz -C /usr/local/bin crictl --version crictl info (shows runtime configuration) Part 2: Installing nerdctl (Full containerd Control) If your cluster runs containerd, nerdctl provides a Docker-like experience for filesystem inspection.
# List snapshots used by the pod's namespace nerdctl -n k8s.io ps -a # Get snapshot size directly (if using buildkit) nerdctl -n k8s.io image ls -a If you find orphaned overlay mounts ( findmnt | grep overlay shows many old pods):