docker 容器内服务随容器自动启动

1. 背景

使用docker运行带有nginx服务的容器。容器启动后，每次都需要手动进入容器内启动nginx服务。修改容器，让nginx服务随容器自动启动。

2. 准备工作

• 使用原nginx-sj: latest镜像文件运行一个容器
  nginx-sj: latest 是我之前使用，已修改的官方nginx镜像文件。

[root@centos7-10 ~]# docker run -it nginx-sj:latest /bin/bash
root@4eb5280856a3:/# 
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• 查看用户目录下.bashrc文件

root@4eb5280856a3:~# pwd
/root
root@4eb5280856a3:~# ls -a
.  ..  .bash_history  .bashrc  .profile  .viminfo
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3. 方式一，直接修改.bashrc文件（简单粗暴）

• 直接将服务启动命名写入.bashrc文件，见下

root@4eb5280856a3:~# vim /root/.bashrc
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# ~/.bashrc: executed by bash(1) for non-login shells.

# Note: PS1 and umask are already set in /etc/profile. You should not
# need this unless you want different defaults for root.
# PS1='${debian_chroot:+($debian_chroot)}\h:\w\$ '
# umask 022

# You may uncomment the following lines if you want 'ls' to be colorized:
# export LS_OPTIONS='--color=auto'
# eval "$(dircolors)"
# alias ls='ls $LS_OPTIONS'
# alias ll='ls $LS_OPTIONS -l'
# alias l='ls $LS_OPTIONS -lA'
#
# Some more alias to avoid making mistakes:
# alias rm='rm -i'
# alias cp='cp -i'
# alias mv='mv -i'

############################################
# start nginx 
if [ -f /etc/init.d/nginx ]; then
        /etc/init.d/nginx start
fi
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4. 方式二，编写启动脚本加入.bashrc文件（文明一点）

• 编辑一个start_nginx.sh文件

root@4eb5280856a3:/# vim /root/start_nginx.sh
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• 写入以下内容，并保存

#!/bin/bash

service nginx start 
#service mysql start    //也可以添加其它服务
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• 添加start_nginx.sh脚本执行权限

root@4eb5280856a3:/# chmod +x /root/start_nginx.sh
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• 将启动脚本写入.bashrc文件

root@4eb5280856a3:~# vim /root/.bashrc
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# ~/.bashrc: executed by bash(1) for non-login shells.

# Note: PS1 and umask are already set in /etc/profile. You should not
# need this unless you want different defaults for root.
# PS1='${debian_chroot:+($debian_chroot)}\h:\w\$ '
# umask 022

# You may uncomment the following lines if you want 'ls' to be colorized:
# export LS_OPTIONS='--color=auto'
# eval "$(dircolors)"
# alias ls='ls $LS_OPTIONS'
# alias ll='ls $LS_OPTIONS -l'
# alias l='ls $LS_OPTIONS -lA'
#
# Some more alias to avoid making mistakes:
# alias rm='rm -i'
# alias cp='cp -i'
# alias mv='mv -i'

############################################
# start nginx 
if [ -f /root/start_nginx.sh ]; then
        /root/start_nginx.sh
fi
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5. 导出容器制作镜像

• 将当前容器（4eb5280856a3）导出成文件nginx-sj_20240222.tar

root@4eb5280856a3:~# exit
exit
[root@centos7-10 ~]# docker ps -a
CONTAINER ID   IMAGE             COMMAND       CREATED          STATUS          PORTS     NAMES
4eb5280856a3   nginx-sj:latest   "/bin/bash"   32 minutes ago   Up 30 minutes             vibrant_mcnulty
[root@centos7-10 ~]# docker export -o nginx-sj_20240222.tar 4eb5280856a3
[root@centos7-10 ~]#
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• 删除当前容器（4eb5280856a3）

[root@centos7-10 ~]# docker ps -a
CONTAINER ID   IMAGE             COMMAND       CREATED          STATUS          PORTS     NAMES
4eb5280856a3   nginx-sj:latest   "/bin/bash"   34 minutes ago   Up 32 minutes             vibrant_mcnulty
[root@centos7-10 ~]# docker stop 4eb5280856a3
4eb5280856a3
[root@centos7-10 ~]# docker container prune
WARNING! This will remove all stopped containers.
Are you sure you want to continue? [y/N] y
Deleted Containers:
4eb5280856a32b83046e8e3be0393028a1a3f328887a11c0ccff15384660f86e

Total reclaimed space: 7.293kB
[root@centos7-10 ~]# 
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• 删除旧nginx-sj:latest镜像

[root@centos7-10 ~]# docker images
REPOSITORY   TAG       IMAGE ID       CREATED             SIZE
nginx-sj     latest    3e97da40406a   About an hour ago   216MB
ubuntu22     latest    caac235feb32   About an hour ago   338MB
busybox      latest    beae173ccac6   2 years ago         1.24MB
redis        latest    7614ae9453d1   2 years ago         113MB
[root@centos7-10 ~]# docker rmi nginx-sj:latest 
Untagged: nginx-sj:latest
Deleted: sha256:3e97da40406a0daaa4d8c0d948b4c3a8a3d099b3aadb0d9fe8a2be4389bd52e6
[root@centos7-10 ~]# 
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• 导入创建新nginx-sj: latest镜像，新镜像ID：283bb24f8ff4

[root@centos7-10 ~]# docker import nginx-sj_20240222.tar nginx-sj:latest
sha256:283bb24f8ff40c67a5ff9d33386847182567f688d7b1b4b109c17054e661b947
[root@centos7-10 ~]# docker images -a nginx-sj:latest 
REPOSITORY   TAG       IMAGE ID       CREATED              SIZE
nginx-sj     latest    283bb24f8ff4   About a minute ago   216MB
[root@centos7-10 ~]# 
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6. 测试导出容器，nginx服务随容器自动启动

• 启动容器，宿主机发布端口：9090，容器内服务端口：80

[root@centos7-10 ~]# docker run -itd --rm  -p 9090:80 nginx-sj:latest /bin/bash
562e64af48bbb26f95f3bf3fd01a3550898ca05292f8d95b9bf604c2000d2953
CONTAINER ID   IMAGE             COMMAND       CREATED         STATUS         PORTS                                   NAMES
562e64af48bb   nginx-sj:latest   "/bin/bash"   3 minutes ago   Up 3 minutes   0.0.0.0:9090->80/tcp, :::9090->80/tcp   nervous_golick
[root@centos7-10 ~]# 
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• 宿主机已监听端口9090
• 宿主机IP 10.211.55.10

[root@centos7-10 ~]# netstat -ntlp | grep 9090
tcp        0      0 0.0.0.0:9090            0.0.0.0:*               LISTEN      17044/docker-proxy  
tcp6       0      0 :::9090                 :::*                    LISTEN      17050/docker-proxy  
[root@centos7-10 ~]# ip a show enp0s5
2: enp0s5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:1c:42:ae:b6:41 brd ff:ff:ff:ff:ff:ff
    inet 10.211.55.10/24 brd 10.211.55.255 scope global noprefixroute dynamic enp0s5
       valid_lft 1140sec preferred_lft 1140sec
    inet6 fdb2:2c26:f4e4:0:233e:38df:2cbd:cec1/64 scope global noprefixroute dynamic 
       valid_lft 2591662sec preferred_lft 604462sec
    inet6 fe80::7e0c:1902:e1ca:4324/64 scope link tentative noprefixroute dadfailed 
       valid_lft forever preferred_lft forever
    inet6 fe80::567a:248b:5e94:5d19/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
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• 访问宿主机HTTP://10.211.55.10:9090，成功！
  

7. 方式三，修改镜像默认值，COMMIT生成新镜像（正规方式）

修改镜像默认值，方式详见官方文档：Overriding image defaults

• 修改镜像Cmd默认值（之前是null）
  • nginx -g “daemon off;”

[root@centos7-10 ~]# docker run -itd -p 9090:80 nginx-sj:latest  nginx -g "daemon off;"
c90c3a7d8e56ea15017fdfa2dfe9b88d398dcfe16f76b9723f0eb884208d6999
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• 提交生成新镜像：nginx-sj:1

[root@centos7-10 ~]# docker commit -m "nginx start" c9 nginx-sj:1
sha256:94fa4087e73dd3c5440f7538d57dcd2f80938e0f9e8f87d48a866f7542f3d685
[root@centos7-10 ~]# docker images
REPOSITORY   TAG       IMAGE ID       CREATED          SIZE
nginx-sj     1         94fa4087e73d   12 seconds ago   216MB
nginx-sj     2         355dbfe22182   30 minutes ago   216MB
nginx-sj     latest    283bb24f8ff4   25 hours ago     216MB
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• 查看新镜像nginx-sj:1信息
  • “Cmd”: [ “nginx”, “-g”, “daemon off;” ],

[root@centos7-10 ~]# docker image inspect nginx-sj:1
[
    {
        "Id": "sha256:94fa4087e73dd3c5440f7538d57dcd2f80938e0f9e8f87d48a866f7542f3d685",
        "RepoTags": [
            "nginx-sj:1"
        ],
        "RepoDigests": [],
        "Parent": "sha256:283bb24f8ff40c67a5ff9d33386847182567f688d7b1b4b109c17054e661b947",
        "Comment": "nginx start",
        "Created": "2024-02-23T09:55:38.972444927Z",
        "Container": "c90c3a7d8e56ea15017fdfa2dfe9b88d398dcfe16f76b9723f0eb884208d6999",
        "ContainerConfig": {
            "Hostname": "c90c3a7d8e56",
......
        "Config": {
            "Hostname": "c90c3a7d8e56",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "ExposedPorts": {
                "80/tcp": {}
            },
            "Tty": true,
            "OpenStdin": true,
            "StdinOnce": false,
            "Env": null,
            "Cmd": [
                "nginx",
                "-g",
                "daemon off;"
            ],
            "Image": "nginx-sj:latest",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": {}
        },
 ......
        }
    }
]
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• 运行容器进行验证

[root@centos7-10 ~]# docker run -itd -p 9000:80 nginx-sj:1 
eae91339bf57739cec9fbbd63890afd8949977eae0a561226109b1f02fd66051
[root@centos7-10 ~]# docker ps -a
CONTAINER ID   IMAGE        COMMAND                   CREATED         STATUS         PORTS                                   NAMES
eae91339bf57   nginx-sj:1   "nginx -g 'daemon of…"   5 seconds ago   Up 4 seconds   0.0.0.0:9000->80/tcp, :::9000->80/tcp   modest_cartwright
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• 宿主机已经监听9000端口–>容器内nginx服务80端口

[root@centos7-10 ~]# netstat -ntlp | grep 9000
tcp        0      0 0.0.0.0:9000            0.0.0.0:*               LISTEN      14995/docker-proxy  
tcp6       0      0 :::9000                 :::*                    LISTEN      15001/docker-proxy  
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• 外部访问HTTP://10.211.55.10:9000，成功。
  

8. 方式四，与方案三类似

• 修改镜像默认值，也可以组合修改ENTRYPOINT 和 CMD。修改方式如下:

[root@centos7-10 ~]# docker run -itd --entrypoint /usr/sbin/nginx nginx-sj:latest -g "daemon off;"
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ENTRYPOINT 与 CMD 关系及使用方式详见官方文档：Understand how CMD and ENTRYPOINT interact

• 生存新镜像方式同方案三

说明：因为docker run 命令中–entrypoint 只支持string，所以建议将服务启动命令写成shell脚本（同方案二），然后使用–entrypoint 引入更合理

9. 方式五，使用DOCKERFILE重新BUILTD新镜像（永久使用方式）

• 创建一个dockerfile文件

[root@centos7-10 ~]# mkdir nginx-sj
[root@centos7-10 ~]# cd nginx-sj
[root@centos7-10 ~]# vim dockerfile-nginx
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• 输入以下内容并保存
  • FROM nginx-sj:latest # 基础镜像
  • MAINTAINER # 维护信息
  • CMD [“nginx”,“-g”,“daemon off;”] # 容器启动执行的默认命令

FROM nginx-sj:latest
MAINTAINER shijin
CMD ["nginx","-g","daemon off;"]
~
~
wq!
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• 使用dockerfile文件创建新镜像
  • -f dockerfile-nginx dockerfile文件名称（注意路径，测试在当前目录下）
  • -t nginx-sj:2024022601 镜像的名称与tag
  • . 指定镜像构建过程中的上下文环境

[root@centos7-10 ~]# docker build -f dockerfile-nginx -t nginx-sj:2024022601 .
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• 查看构建镜像结果

[root@centos7-10 nginx-sj]# docker images
REPOSITORY   TAG          IMAGE ID       CREATED          SIZE
nginx-sj     2024022601   64b3c38d4483   36 minutes ago   216MB
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[root@centos7-10 nginx-sj]# docker history  nginx-sj:2024022601 
IMAGE          CREATED          CREATED BY                         SIZE      COMMENT
64b3c38d4483   53 minutes ago   CMD ["nginx" "-g" "daemon off;"]   0B        buildkit.dockerfile.v0
<missing>      53 minutes ago   MAINTAINER shijin                  0B        buildkit.dockerfile.v0
<missing>      53 minutes ago                                      216MB     Imported from -
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总结：

1. 如果临时使用，可以采用方式一、二，从容器中导出；
2. 如果不频繁变更，可以采用方式三、四，直接commit生成新镜像；
3. 如果要长期或永久使用，建议采用方式五，彻底重新build新镜像。