实战Containerd系列之2 部署容器运行时Containerd

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1 Containerd启动容器涉及的模块

前面我们梳理了docker、k8s、containerd、runc之间的渊源,Containerd早已脱离Docker成为了一个稳定可靠的容器运行时。

单从containerd的角度来看启动一个容器的过程大致是下图所示的流程:

实战Containerd系列之2 部署容器运行时Containerd

我们可以使用Containerd的命令行工具ctr来启动一个容器,也可以在我们的应用中编写客户端程序为我们的应用加入启动容器的功能。

从containerd作为k8s的容器运行时来看,启动一个容器的过程大致是下图所示流程:

实战Containerd系列之2 部署容器运行时Containerd

containerd实现了k8s的CRI接口,提供容器运行时核心功能,如镜像管理、容器管理等,当前containerd实现CRI接口的代码位于containerd代码的pkg/cri包下。 也就是说containerd同样是一个k8s CRI的实现,可以使用k8s提供的cri-tools中的crictl命令行工具与containerd的CRI实现交互。

理解了上面这两幅图中各个组件之间的交互关系,接下来就可以部署containerd相关组件。

2 二进制部署containerd

下载安装包

wget https://github.com/opencontainers/runc/releases/download/v1.0.0-rc93/runc.amd64
wget https://github.com/containerd/containerd/releases/download/v1.4.4/containerd-1.4.4-linux-amd64.tar.gz
wget https://github.com/kubernetes-sigs/cri-tools/releases/download/v1.21.0/crictl-v1.21.0-linux-amd64.tar.gz

runc.amd64是runc的二进制文件

containerd-1.4.4-linux-amd64.tar.gz 包含 containerd 和它的 containerd-shim 以及命令行工具 ctr

crictl-v1.21.0-linux-amd64.tar.gz 包含 CRI 的命令行工具 crictl

下一步进行二进制文件的解压和安装:

mkdir /usr/local/containerd
mkdir /etc/containerd

mv runc.amd64 /usr/local/containerd/bin/runc
chmod +x /usr/local/containerd/bin/runc
tar -zxvf containerd-1.4.4-linux-amd64.tar.gz -C /usr/local/containerd
tar -zxvf crictl-v1.21.0-linux-amd64.tar.gz -C /usr/local/containerd/bin

ln -s /usr/local/containerd/bin/containerd /usr/local/bin/containerd
ln -s /usr/local/containerd/bin/ctr /usr/local/bin/ctr
ln -s /usr/local/containerd/bin/runc /usr/local/bin/runc
ln -s /usr/local/containerd/bin/crictl /usr/local/bin/crictl

安装的目录接口如下:

tree /usr/local/containerd/
/usr/local/containerd/
└── bin    
    ├── containerd
    ├── containerd-shim
    ├── containerd-shim-runc-v1    
    ├── containerd-shim-runc-v2
    ├── crictl
    ├── ctr
    └── runc

下一步生成containerd的默认配置文件/etc/containerd/config.toml

containerd config default > /etc/containerd/config.toml

查看一下配置文件(篇幅有限这里没有给出全部内容)

root@VM-16-16-centos ~]# cat /etc/containerd/config.toml 
version = 2
root = "/var/lib/containerd"
state = "/run/containerd"
plugin_dir = ""
disabled_plugins = []
required_plugins = []
oom_score = 0

[grpc]
  address = "/run/containerd/containerd.sock"
  tcp_address = ""
  tcp_tls_cert = ""
  tcp_tls_key = ""
  uid = 0
  gid = 0
  max_recv_message_size = 16777216
  max_send_message_size = 16777216

[ttrpc]
  address = ""
  uid = 0
  gid = 0

[debug]
  address = ""
  uid = 0
  gid = 0
  level = ""

创建 containerd 进程的 systemd 服务配置 containerd.service,containerd 源码的根目录中也给出了containerd.service这个文件的示例

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

[Service]
ExecStartPre=-/sbin/modprobe overlay
ExecStart=/usr/local/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=1048576
# 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
EOF

启动 containerd

# systemctl start containerd
# systemctl enable containerd
# systemctl status containerd
● containerd.service - containerd container runtime
   Loaded: loaded (/etc/systemd/system/containerd.service; enabled; vendor preset: disabled)
   Active: active (running) since Thu 2023-02-16 15:08:44 CST; 10s ago
     Docs: https://containerd.io
 Main PID: 13291 (containerd)
   CGroup: /system.slice/containerd.service
           └─13291 /usr/local/bin/containerd

3 ctr 命令工具使用

3.1 打印服务端和客户端版本

[root@VM-16-16-centos ~]# ctr version
Client:
  Version:  v1.4.4
  Revision: 05f951a3781f4f2c1911b05e61c160e9c30eaa8e
  Go version: go1.15.8

Server:
  Version:  v1.4.4
  Revision: 05f951a3781f4f2c1911b05e61c160e9c30eaa8e
  UUID: f4d6ec71-79e8-44d2-ad92-333b369aae79

3.2 pull docker hub中的redis镜像

# pull镜像
ctr images pull docker.io/library/redis:alpine3.13

# 查看镜像
ctr i ls

3.3 pull私有仓库的镜像

需要使用-u <username>:<password>给定镜像仓库的用户名和密码

ctr images pull -u user:password own.harbor.xxx.com/library/nginx:1.1

3.4 启动redis容器

ctr run -d docker.io/library/redis:alpine3.13 redis

3.5 查看容器

ctr task ls
TASK     PID      STATUS    
redis    14348    RUNNING

ctr container ls
CONTAINER    IMAGE                                 RUNTIME                  
redis        docker.io/library/redis:alpine3.13    io.containerd.runc.v2 

注意: 在 containerd 中,container 和 task 是分离的,container 描述的是容器分配和附加资源的元数据对象,是静态内容,task 是任务是系统上一个活动的、正在运行的进程。 task 应该在每次运行后删除,而 container可以被多次使用、更新和查询。这点和 docker 中 container 定义是不一样的

3.6 进入到容器中

ctr task exec -t --exec-id redis-sh redis sh
/data # redis-cli
127.0.0.1:6379> ping
PONG
127.0.0.1:6379>

3.7 查看进程信息

ps -ef | grep runc | grep redis
/usr/local/containerd/bin/containerd-shim-runc-v2 -namespace default -id redis -address /run/containerd/containerd.sock

可以看出containerd中是存在namespace概念的,这样可以将不同业务和应用进行隔离,例如k8s使用containerd和直接使用ctr创建的容器可以隔离开。查看一下当前的namespace

[root@VM-16-16-centos ~]# ctr ns ls
NAME    LABELS 
default

不同namespace下pull的镜像也是隔离显示的,可以使用-n指定具体的namespace

ctr -n default i ls
ctr -n k8s.io i ls

4 crictl命令行工具配置

crictlk8s cri-tools的一部分,它提供了类似于docker的命令行工具,不需要kubelet就可以通过CRI跟容器运行时通信。 crictl是专门为k8s设计的,提供了Pod、容器和镜像等资源的管理命令,可以帮助用户调试容器应用或者排查异常问题。 crictl 可以用于所有实现了CRI接口的容器运行时

尝试使用ctictl命令行工具查看一下镜像,给了一个警告信息

[root@VM-16-16-centos ~]# crictl images
WARN[0000] image connect using default endpoints: [unix:///var/run/dockershim.sock unix:///run/containerd/containerd.sock unix:///run/crio/crio.sock]. As the default settings are now deprecated, you should set the endpoint instead. 
ERRO[0002] connect endpoint 'unix:///var/run/dockershim.sock', make sure you are running as root and the endpoint has been started: context deadline exceeded 
IMAGE               TAG                 IMAGE ID            SIZE

需要我们显示配置默认的endpoints

crictl config runtime-endpoint unix:///run/containerd/containerd.sock
crictl config image-endpoint unix:///run/containerd/containerd.sock

上面的命令执行完成后将生成配置文件/etc/crictl.yaml

[root@VM-16-16-centos ~]# cat /etc/crictl.yaml 
runtime-endpoint: "unix:///run/containerd/containerd.sock"
image-endpoint: "unix:///run/containerd/containerd.sock"
timeout: 0
debug: false
pull-image-on-create: false
disable-pull-on-run: false

4.1 pull 镜像

crictl pull docker.io/library/redis:alpine3.13
[root@VM-16-16-centos ~]# crictl images
IMAGE                     TAG                 IMAGE ID            SIZE
docker.io/library/redis   alpine3.13          1690b63e207f6       10.9MB

crictl pull的镜像实际上是在k8s.io namespace下,可以使用ctr -n k8s.io i ls查看

crictl不能像ctr那样通过参数给定用户名和密码的方式从开启认证的私有仓库中pull镜像。需要对containerd进行配置。 containerd提供的各种功能在其内部都是通过插件实现的,可以使用ctr plugins ls查看

root@VM-16-16-centos ~]# ctr plugins ls
TYPE                            ID                       PLATFORMS      STATUS    
io.containerd.content.v1        content                  -              ok        
io.containerd.snapshotter.v1    aufs                     linux/amd64    error     
io.containerd.snapshotter.v1    btrfs                    linux/amd64    error     
io.containerd.snapshotter.v1    devmapper                linux/amd64    error     
io.containerd.snapshotter.v1    native                   linux/amd64    ok        
io.containerd.snapshotter.v1    overlayfs                linux/amd64    ok        
io.containerd.snapshotter.v1    zfs                      linux/amd64    error     
io.containerd.metadata.v1       bolt                     -              ok        
io.containerd.differ.v1         walking                  linux/amd64    ok        
io.containerd.gc.v1             scheduler                -              ok        
io.containerd.service.v1        introspection-service    -              ok        
io.containerd.service.v1        containers-service       -              ok        
io.containerd.service.v1        content-service          -              ok        
io.containerd.service.v1        diff-service             -              ok        
io.containerd.service.v1        images-service           -              ok        
io.containerd.service.v1        leases-service           -              ok        
io.containerd.service.v1        namespaces-service       -              ok        
io.containerd.service.v1        snapshots-service        -              ok        
io.containerd.runtime.v1        linux                    linux/amd64    ok        
io.containerd.runtime.v2        task                     linux/amd64    ok        
io.containerd.monitor.v1        cgroups                  linux/amd64    ok        
io.containerd.service.v1        tasks-service            -              ok        
io.containerd.internal.v1       restart                  -              ok        
io.containerd.grpc.v1           containers               -              ok        
io.containerd.grpc.v1           content                  -              ok        
io.containerd.grpc.v1           diff                     -              ok        
io.containerd.grpc.v1           events                   -              ok        
io.containerd.grpc.v1           healthcheck              -              ok        
io.containerd.grpc.v1           images                   -              ok        
io.containerd.grpc.v1           leases                   -              ok        
io.containerd.grpc.v1           namespaces               -              ok        
io.containerd.internal.v1       opt                      -              ok        
io.containerd.grpc.v1           snapshots                -              ok        
io.containerd.grpc.v1           tasks                    -              ok        
io.containerd.grpc.v1           version                  -              ok        
io.containerd.grpc.v1           cri                      linux/amd64    ok        

私有镜像仓库相关的配置在cri插件中,文档Configure Image Registry中包含了镜像仓库的配置。

关于私有仓库和认证信息配置示例如下,修改/etc/containerd/config.toml

...
[plugins]
...
  [plugins."io.containerd.grpc.v1.cri"]
  ...
    [plugins."io.containerd.grpc.v1.cri".registry]
      [plugins."io.containerd.grpc.v1.cri".registry.mirrors]
        [plugins."io.containerd.grpc.v1.cri".registry.mirrors."docker.io"]
          endpoint = ["https://registry-1.docker.io"]
        [plugins."io.containerd.grpc.v1.cri".registry.mirrors."harbor.my.org"]
          endpoint = ["https://harbor.my.org"]
      [plugins."io.containerd.grpc.v1.cri".registry.configs]
        [plugins."io.containerd.grpc.v1.cri".registry.configs."harbor.my.org".tls]
          insecure_skip_verify = true
        [plugins."io.containerd.grpc.v1.cri".registry.configs."harbor.my.org".auth]
          username = "username"
          password = "passwd"
          # auth = "base64(username:password)"
...

配置完成后重启containerd,就可以使用crictl pull配置的私有仓库的镜像了

5 总结

我们已经部署了containerd,配置好了ctr和crictl工具,并使用ctr启动了第一个测试容器,但是此时容器还不具备网络能力,只能在容器内部自己玩。 下一步,将尝试手工配置containerd和cni及cni插件的集成,为容器加入基本的网络能力。

正文完
 
mervinwang
版权声明:本站原创文章,由 mervinwang 2023-02-22发表,共计8301字。
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