sealer

# What is CloudRootfs

All the files which run a kubernetes cluster needs.

Contains:

  • Bin files, like docker containerd crictl kubeadm kubectl...
  • Config files, like kubelet systemd config, docker systemd config, docker daemon.json...
  • Registry docker image
  • Some Metadata, like Kubernetes version.
  • Registry files, contains all the docker image, like kubernetes core component docker images...
  • Scripts, some shell script using to install docker and kubelet... sealer will call init.sh and clean.sh.
  • Other static files
.
├── bin
│   ├── conntrack
│   ├── containerd-rootless-setuptool.sh
│   ├── containerd-rootless.sh
│   ├── crictl
│   ├── kubeadm
│   ├── kubectl
│   ├── kubelet
│   ├── nerdctl
│   └── seautil
├── cri
│   ├── containerd
│   ├── containerd-shim
│   ├── containerd-shim-runc-v2
│   ├── ctr
│   ├── docker
│   ├── dockerd
│   ├── docker-init
│   ├── docker-proxy
│   ├── rootlesskit
│   ├── rootlesskit-docker-proxy
│   ├── runc
│   └── vpnkit
├── etc
│   ├── 10-kubeadm.conf
│   ├── Clusterfile  # image default Clusterfile
│   ├── daemon.json
│   ├── docker.service
│   ├── kubeadm-config.yaml
│   └── kubelet.service
├── images
│   └── registry.tar  # registry docker image, will load this image and run a local registry in cluster
├── Kubefile
├── Metadata
├── README.md
├── registry # will mount this dir to local registry
│   └── docker
│       └── registry
├── scripts
│   ├── clean.sh
│   ├── docker.sh
│   ├── init-kube.sh
│   ├── init-registry.sh
│   ├── init.sh
│   └── kubelet-pre-start.sh
└── statics # yaml files, sealer will render values in those files
    └── audit-policy.yml

# How can I get CloudRootfs

  1. Pull a BaseImage sealer pull kubernetes:v1.19.8-alpine
  2. View the image layer information sealer inspect kubernetes:v1.19.8-alpine
  3. Get into the BaseImage Layer ls /var/lib/sealer/data/overlay2/{layer-id}

You will found the CloudRootfs layer.

# Build your own BaseImage

You can edit any files in CloudRootfs you want, for example you want to define your own docker daemon.json, just edit it and build a new CloudImage.

FROM scratch
COPY . .

sealer build -t user-defined-kubernetes:v1.19.8 .

Then you can use this image as a BaseImage.

# OverWrite CloudRootfs files

Sometimes you don't want to care about the CloudRootfs context, but need custom some config.

You can use kubernetes:v1.19.8 as BaseImage, and use your own config file to overwrite the default file in CloudRootfs.

For example: daemon.json is your docker engine config, using it to overwrite default config:

FROM kubernetes:v1.19.8
COPY daemon.json etc/

sealer build -t user-defined-kubernetes:v1.19.8 .

← Clusterfile →