How to use nerdctl if you are familiar with Docker CLI

nerdctl is a relatively new command-line client for containerd. Unlike ctr, nerdctl aims to be user-friendly and Docker-compatible. To some extent, nerdctl + containerd can seamlessly replace docker + dockerd. However, [this does not seem to be the main goal of the project(https://medium.com/nttlabs/nerdctl-359311b32d0e)].

From the basic usage standpoint, comparing to ctr, nerdctl supports:

Image building with nerdctl build (BuildKit required) Container networking management
Docker Compose with nerdctl compose up

And the coolest part about it isthat nerdctl tries to provide the identical to docker command-line UX. So, if you are familiar with docker CLI,you are allready familiar with nerdctl.

Basic usage

To run a container with the default bridge CNI network (10.4.0.0/24):

# nerdctl run -it --rm alpine

To build an image using BuildKit:

# nerdctl build -t foo /some-dockerfile-directory
# nerdctl run -it --rm foo

To build and send output to a local directory using BuildKit:

# nerdctl build -o type=local,dest=. /some-dockerfile-directory

To run containers from docker-compose.yaml:

# nerdctl compose -f ./examples/compose-wordpress/docker-compose.yaml up

Debugging Kubernetes

To list local Kubernetes containers:

# nerdctl --namespace k8s.io ps -a

To build an image for local Kubernetes without using registry:

# nerdctl --namespace k8s.io build -t foo /some-dockerfile-directory
# kubectl apply -f - <<EOF
apiVersion: v1
kind: Pod
metadata:
  name: foo
spec:
  containers:
    - name: foo
      image: foo
      imagePullPolicy: Never
EOF

To load an image archive (docker save format or OCI format) into local Kubernetes:

# nerdctl --namespace k8s.io load < /path/to/image.tar

To read logs (experimental):

# nerdctl --namespace=k8s.io ps -a
CONTAINER ID    IMAGE                                                      COMMAND                   CREATED          STATUS    PORTS    NAMES
...
e8793b8cca8b    registry.k8s.io/coredns/coredns:v1.9.3                     "/coredns -conf /etc…"    2 minutes ago    Up                 k8s://kube-system/coredns-787d4945fb-mfx6b/coredns
...

# nerdctl --namespace=k8s.io logs -f e8793b8cca8b
[INFO] plugin/reload: Running configuration SHA512 = 591cf328cccc12bc490481273e738df59329c62c0b729d94e8b61db9961c2fa5f046dd37f1cf888b953814040d180f52594972691cd6ff41be96639138a43908
CoreDNS-1.9.3
linux/amd64, go1.18.2, 45b0a11
...

Source:
https://labs.iximiuz.com/courses/containerd-cli/nerdctl/nerdctl
https://github.com/containerd/nerdctl/blob/main/README.md

Check:
https://labs.iximiuz.com/courses/containerd-cli/crictl/crictl

Last updated on 20 Jun 2023
Published on 20 Jun 2023
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