容器引擎说明——Contianerd与Docker的区别以及Containerd换源操作

容器引擎是Kubernetes最重要的组件之一，负责管理镜像和容器的生命周期。Kubelet通过Container Runtime Interface (CRI) 与容器引擎交互，以管理镜像和容器。

表1 容器引擎对比

Containerd和Docker组件常用命令对比#

表2 镜像相关功能

表3 容器相关功能

表4 Pod相关功能

说明：
Containerd创建并启动的容器会被kubelet立即删除，不支持暂停、恢复、重启、重命名、等待容器，Containerd不具备docker构建、导入、导出、比较、推送、查找、打标签镜像的能力，Containerd不支持复制文件，可通过修改containerd的配置文件实现登录镜像仓库。

调用链区别#

Docker（Kubernetes 1.23及以下版本）：
kubelet --> docker shim （在kubelet 进程中） --> docker --> containerd
Docker（Kubernetes 1.24及以上版本社区方案）：
kubelet --> cri-dockerd （kubelet使用cri接口对接cri-dockerd） --> docker --> containerd
Containerd：
kubelet --> cri plugin（在containerd进程中） --> containerd

其中Docker虽增加了swarm cluster、docker build、docker API等功能，但也会引入一些bug，并且与Containerd相比，多了一层调用，因此Containerd被认为更加节省资源且更安全。

Contianerd换源#

Containerd通过在启动时指定一个配置文件夹，使后续所有镜像仓库相关的配置都可以在里面热加载，无需重启Containerd。

如果/etc/containerd/config.toml配置文件中已包含config_path配置（例如"/etc/containerd/cert.d"），则无需执行此步骤；如果不存在，您可以在配置文件中添加以下config_path并重启Containerd使更改生效。

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config_path = "/etc/containerd/certs.d"

在步骤一中指定的config_path路径中创建docker.io/hosts.toml文件。
在文件中写入如下配置。

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server = "https://registry-1.docker.io"

[host."$(镜像加速器地址，如https://xxx.mirror.aliyuncs.com)"]
  capabilities = ["pull", "resolve", "push"]

镜像加速配置：

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# docker hub镜像加速
mkdir -p /etc/containerd/certs.d/docker.io
cat > /etc/containerd/certs.d/docker.io/hosts.toml << EOF
server = "https://docker.io"
[host."https://dockerproxy.com"]
  capabilities = ["pull", "resolve"]

[host."https://docker.m.daocloud.io"]
  capabilities = ["pull", "resolve"]

[host."https://reg-mirror.qiniu.com"]
  capabilities = ["pull", "resolve"]

[host."https://registry.docker-cn.com"]
  capabilities = ["pull", "resolve"]

[host."http://hub-mirror.c.163.com"]
  capabilities = ["pull", "resolve"]

EOF

# registry.k8s.io镜像加速
mkdir -p /etc/containerd/certs.d/registry.k8s.io
tee /etc/containerd/certs.d/registry.k8s.io/hosts.toml << 'EOF'
server = "https://registry.k8s.io"

[host."https://k8s.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF

# docker.elastic.co镜像加速
mkdir -p /etc/containerd/certs.d/docker.elastic.co
tee /etc/containerd/certs.d/docker.elastic.co/hosts.toml << 'EOF'
server = "https://docker.elastic.co"

[host."https://elastic.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF

# gcr.io镜像加速
mkdir -p /etc/containerd/certs.d/gcr.io
tee /etc/containerd/certs.d/gcr.io/hosts.toml << 'EOF'
server = "https://gcr.io"

[host."https://gcr.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF

# ghcr.io镜像加速
mkdir -p /etc/containerd/certs.d/ghcr.io
tee /etc/containerd/certs.d/ghcr.io/hosts.toml << 'EOF'
server = "https://ghcr.io"

[host."https://ghcr.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF

# k8s.gcr.io镜像加速
mkdir -p /etc/containerd/certs.d/k8s.gcr.io
tee /etc/containerd/certs.d/k8s.gcr.io/hosts.toml << 'EOF'
server = "https://k8s.gcr.io"

[host."https://k8s-gcr.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF

# mcr.m.daocloud.io镜像加速
mkdir -p /etc/containerd/certs.d/mcr.microsoft.com
tee /etc/containerd/certs.d/mcr.microsoft.com/hosts.toml << 'EOF'
server = "https://mcr.microsoft.com"

[host."https://mcr.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF

# nvcr.io镜像加速
mkdir -p /etc/containerd/certs.d/nvcr.io
tee /etc/containerd/certs.d/nvcr.io/hosts.toml << 'EOF'
server = "https://nvcr.io"

[host."https://nvcr.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF

# quay.io镜像加速
mkdir -p /etc/containerd/certs.d/quay.io
tee /etc/containerd/certs.d/quay.io/hosts.toml << 'EOF'
server = "https://quay.io"

[host."https://quay.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF

# registry.jujucharms.com镜像加速
mkdir -p /etc/containerd/certs.d/registry.jujucharms.com
tee /etc/containerd/certs.d/registry.jujucharms.com/hosts.toml << 'EOF'
server = "https://registry.jujucharms.com"

[host."https://jujucharms.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF

# rocks.canonical.com镜像加速
mkdir -p /etc/containerd/certs.d/rocks.canonical.com
tee /etc/containerd/certs.d/rocks.canonical.com/hosts.toml << 'EOF'
server = "https://rocks.canonical.com"

[host."https://rocks-canonical.m.daocloud.io"]
  capabilities = ["pull", "resolve", "push"]
EOF