[Docker学习笔记] Docker体系结构、镜像和容器的关系

我不是女神ヾ 2021-11-10 16:16 256阅读 0赞

1）看docker的进程树：

**ps axjf**

[root@localhost ~]# docker run -d busybox ping baidu.com
    docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.
    See 'docker run --help'.
    [root@localhost ~]#
    [root@localhost ~]# systemctl start docker
    [root@localhost ~]#
    [root@localhost ~]# docker ps
    CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
    [root@localhost ~]#
    [root@localhost ~]# docker run -d busybox ping baidu.com
    Unable to find image 'busybox:latest' locally
    latest: Pulling from library/busybox
    ee153a04d683: Pull complete
    Digest: sha256:9f1003c480699be56815db0f8146ad2e22efea85129b5b5983d0e0fb52d9ab70
    Status: Downloaded newer image for busybox:latest
    ebb7c712dea23c035ae4bb3260db8217ef69ae2723258ab159e14e531fdbb18d
    [root@localhost ~]#
    [root@localhost ~]#
    [root@localhost ~]# ps -ef | grep docker
    root       1711      1  1 15:20 ?        00:00:02 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
    root       1906   1709  0 15:21 ?        00:00:00 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/ebb7c712dea23c035ae4bb3260db8217ef69ae2723258ab159e14e531fdbb18d -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
    root       1965   1642  0 15:23 pts/0    00:00:00 grep --color=auto docker
    [root@localhost ~]#
    [root@localhost ~]# ps axjf -p 1711
      PPID    PID   PGID    SID TTY       TPGID STAT   UID   TIME COMMAND
    ……
         1   1709   1709   1709 ?            -1 Ssl      0   0:01 /usr/bin/containerd
      1709   1906   1906   1709 ?            -1 Sl       0   0:00  \_ containerd-shim -namespace moby -workdir /var/lib/containerd/
      1906   1921   1921   1921 ?            -1 Ss       0   0:00      \_ ping baidu.com
         1   1711   1711   1711 ?            -1 Ssl      0   0:02 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd
    [root@localhost ~]#

说明：docker client 将命令传给docker engine，本地有镜像则用本地的，没有则从image repository拉取。docker engine通知containerd进程创建容器，containerd启动shim创建容器，runC提供文件系统以提供容器运行环境。

**设置开机自启动：**

[root@localhost test]# systemctl enable docker
    Created symlink from /etc/systemd/system/multi-user.target.wants/docker.service to /usr/lib/systemd/system/docker.service.

2）内部组件

Namespace 命名空间  -> 容器内部只能看到自己的进程，不能看到宿主机的进程

CGroup 控制组  -> 对资源限制，如CPU、内存、网络等

UnionFS 联合文件系统  -> 镜像中的目录结构的分层

3）kill 所有容器：

**docker rm -f $(docker ps -q -a)**

其中，-q, --quiet           Only display numeric IDs

例如，\# docker ps -a -q，打印结果为 d96a8a2382a8

[root@localhost ~]# docker ps
    CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
    ebb7c712dea2        busybox             "ping baidu.com"    23 minutes ago      Up 23 minutes                           agitated_brahmagupta
    [root@localhost ~]#
    [root@localhost ~]# docker images
    REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
    busybox             latest              db8ee88ad75f        2 weeks ago         1.22MB
    hello-world         latest              fce289e99eb9        7 months ago        1.84kB
    [root@localhost ~]#
    [root@localhost ~]# docker rm -f $(docker ps -q -a)
    ebb7c712dea2
    c38ba80a5520
    a7fe13e2c182
    [root@localhost ~]# docker ps
    CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
    [root@localhost ~]#
    [root@localhost ~]# docker ps --help
    
    Usage:  docker ps [OPTIONS]
    
    List containers
    
    Options:
      -a, --all             Show all containers (default shows just running)
      -f, --filter filter   Filter output based on conditions provided
          --format string   Pretty-print containers using a Go template
      -n, --last int        Show n last created containers (includes all states) (default -1)
      -l, --latest          Show the latest created container (includes all states)
          --no-trunc        Don't truncate output
      -q, --quiet           Only display numeric IDs
      -s, --size            Display total file sizes

4）docker pull 很慢，可以在 Docker 守护进程启动时传入 --registry-mirror 参数

为了永久性保留更改，可以修改 /etc/docker/daemon.json 文件的 registry-mirrors 键值。

[root@localhost ~]# cat /etc/docker/daemon.json
    {
    "registry-mirrors":["https://registry.docker-cn.com"]
    }
    [root@localhost ~]#
    [root@localhost ~]# vi /etc/docker/daemon.json
    [root@localhost ~]#
    [root@localhost ~]# systemctl daemon-reload
    [root@localhost ~]# systemctl restart docker
    [root@localhost ~]#
    [root@localhost ~]# dcoker pull nginx
    -bash: dcoker: command not found
    [root@localhost ~]#
    [root@localhost ~]# docker pull nginx
    Using default tag: latest
    latest: Pulling from library/nginx
    f5d23c7fed46: Pull complete
    918b255d86e5: Pull complete
    8c0120a6f561: Pull complete
    Digest: sha256:eb3320e2f9ca409b7c0aa71aea3cf7ce7d018f03a372564dbdb023646958770b
    Status: Downloaded newer image for nginx:latest
    docker.io/library/nginx:latest
    [root@localhost ~]#

参考：docker加速 阿里云镜像地址，使用方式 [https://blog.csdn.net/qq\_28410283/article/details/81433674][https_blog.csdn.net_qq_28410283_article_details_81433674]

5）镜像由多层构成，可以用 docker history 查看

docker image history nginx 和 docker history nginx 的返回结果一样~

[root@localhost ~]# docker history nginx
    IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
    e445ab08b2be        2 weeks ago         /bin/sh -c #(nop)  CMD ["nginx" "-g" "daemon…   0B
    <missing>           2 weeks ago         /bin/sh -c #(nop)  STOPSIGNAL SIGTERM           0B
    <missing>           2 weeks ago         /bin/sh -c #(nop)  EXPOSE 80                    0B
    <missing>           2 weeks ago         /bin/sh -c ln -sf /dev/stdout /var/log/nginx…   22B
    <missing>           2 weeks ago         /bin/sh -c set -x     && addgroup --system -…   56.6MB
    <missing>           2 weeks ago         /bin/sh -c #(nop)  ENV PKG_RELEASE=1~buster     0B
    <missing>           2 weeks ago         /bin/sh -c #(nop)  ENV NJS_VERSION=0.3.3        0B
    <missing>           2 weeks ago         /bin/sh -c #(nop)  ENV NGINX_VERSION=1.17.2     0B
    <missing>           2 weeks ago         /bin/sh -c #(nop)  LABEL maintainer=NGINX Do…   0B
    <missing>           4 weeks ago         /bin/sh -c #(nop)  CMD ["bash"]                 0B
    <missing>           4 weeks ago         /bin/sh -c #(nop) ADD file:71ac26257198ecf6a…   69.2MB

6）容器是在镜像的基础上添加一个读写层。以CentOS 7为例，镜像存储在 /var/lib/docker/overlay2，存有镜像每一层的数据。

说明：overlay2是存储驱动

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d5X2hoeHg_size_16_color_FFFFFF_t_70][]

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[https_blog.csdn.net_qq_28410283_article_details_81433674]: https://blog.csdn.net/qq_28410283/article/details/81433674
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d5X2hoeHg_size_16_color_FFFFFF_t_70]: /images/20211109/145231843b6242369e5387fe450e863f.png
[https_ke.qq.com_course_366769]: https://ke.qq.com/course/366769