containerd简介

containerd是一个标准的容器运行时，它强调简单性、健壮性和可移植性，containerd主要可以实现以下功能：

• 容器生命周期管理（从创建到删除）
• 容器镜像pull和push
• 存储管理（管理镜像和容器数据的存储）
• 管理容器网络接口及网络
• 与容器运行时进行交互（比如调用runc运行容器）

containerd的目的并不是面向最终用户，而是为了集成到更上层的系统中，例如Swarm、Kubernetes、Mesos等容器编排系统。

安装

下载安装包

这里采用二进制安装的方式，首先到github下载containerd的安装包：https://github.com/containerd/containerd/releases

wget https://github.com/containerd/containerd/releases/download/v1.6.6/containerd-1.6.6-linux-amd64.tar.gz
mkdir /tmp/containerd/
tar xvf containerd-1.6.6-linux-amd64.tar.gz -C /tmp/containerd/
cp /tmp/containerd/bin/* /usr/bin/

准备contained.service文件

cat /lib/systemd/system/containerd.service
[Unit]
Description=containerd container runtime
Documentation=https://containerd.io
After=network.target local-fs.target

[Service]
#uncomment to enable the experimental sbservice (sandboxed) version of containerd/cri integration
#Environment="ENABLE_CRI_SANDBOXES=sandboxed"
ExecStartPre=-/sbin/modprobe overlay
ExecStart=/usr/bin/containerd

Type=notify
Delegate=yes
KillMode=process
Restart=always
RestartSec=5
# Having non-zero Limit*s causes performance problems due to accounting overhead
# in the kernel. We recommend using cgroups to do container-local accounting.
LimitNPROC=infinity
LimitCORE=infinity
LimitNOFILE=infinity
# Comment TasksMax if your systemd version does not supports it.
# Only systemd 226 and above support this version.
TasksMax=infinity
OOMScoreAdjust=-999

[Install]
WantedBy=multi-user.target

准备配置文件

containerd的默认配置文件为/etc/containerd/config.toml，可以通过下面的命令生成一个默认配置，然后配置一下镜像加速：

mkdir /etc/containerd
containerd config default > /etc/containerd/config.toml
cat /etc/containerd/config.toml	#添加了镜像加速配置
153       [plugins."io.containerd.grpc.v1.cri".registry.mirrors]
154         [plugins."io.containerd.grpc.v1.cri".registry.mirrors."docker.io"]
155           endpoint=[
156             "http://docker.mirrors.ustc.edu.cn",
157             "http://hub-mirror.c.163.com"
158           ]

部署runc

wget https://github.com/opencontainers/runc/releases/download/v1.1.3/runc.amd64 -O /usr/bin/runc
chmod +x /usr/bin/runc

测试

启动服务

systemctl daemon-reload
systemctl start containerd

下载镜像启动容器

ctr images pull docker.io/library/alpine:latest
ctr run -t --net-host docker.io/library/alpine:latest test-container sh

containerd命令行工具

因为containerd提供的ctr命令比较简单，所以推荐使用nerdctl命令来代替ctr命令，nerdctl的github地址是：https://github.com/containerd/nerdctl

安装nerdctl

wget https://github.com/containerd/nerdctl/releases/download/v0.22.0/nerdctl-0.22.0-linux-amd64.tar.gz
tar xvf nerdctl-0.22.0-linux-amd64.tar.gz
cp nerdctl /usr/bin/
nerdctl version

安装cni

wget https://github.com/containernetworking/plugins/releases/download/v1.1.1/cni-plugins-linux-amd64-v1.1.1.tgz
mkdir -p /opt/cni/bin
tar xvf cni-plugins-linux-amd64-v1.1.1.tgz -C /opt/cni/bin/

使用nerdct下载镜像启动容器

nerdctl pull nginx
nerdctl run -d -p 80:80 --name nginx --restart=always nginx
nerdctl exec -it nginx sh