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Docker image overview
- Three ways to make Docker images
- Dockerfile
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Docker image overview

I have written some theories about Docker and the theory about mirroring in the previous blog. If you need it, you can directly read the previous Weibo.
Here is the link to the previous Weibo, click me to jump! !

Three ways to make Docker images

Create based on an existing image
Create based on local template
Based on the Dockerfile
, each instruction in the Dockerfile will create a new mirror layer. The
mirror layer will be cached and reused.
When the Dockerfile instructions are modified, the copied file changes, or the variables specified when building the mirror are different, the corresponding mirror layer is cached It will be invalidated. After
a certain layer of mirroring cache fails, the subsequent mirroring layer caches will be invalidated. The
mirroring layer is immutable. If you add a file to one layer and then delete it in the next layer, the mirroring remains Will contain the article

Dockerfile

Dockerfile is a file composed of a set of instructions. The
Dockerfile structure is divided into four parts:

Basic image information
Maintainer information
Mirror operation instructions
Specify instructions when the container starts

Show it directly!

Mirror establishment

1. Create based on an existing image

Package the program and operating environment running in the container into a new image
docker commit option Container ID/name warehouse name: label
Common options:
-m description information
-a author information
-p stop the operation of the container during the generation process

[root@5centos ~]# docker create -it centos:8 /bin/bash	##创建容器
d61a1f121f3a48ed81ef00da86bb7c573f81235a1fcffb6115e439fd64c328bd
[root@5centos ~]# docker ps -a	##查看ID
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
d61a1f121f3a        centos:8            "/bin/bash"         30 seconds ago      Created                                 wizardly_varahamihira
[root@5centos ~]# docker commit -m "基于镜像建" -a "橘籽酱" d61a1f121f3a oracentos:8		##基于已有容器镜像创建
sha256:cd067ed5ce2254d10b1d7f96b97ba371cfac18899e53b1d39594ac56dd21f73b
[root@5centos ~]# docker images	##查看镜像
REPOSITORY           TAG                 IMAGE ID            CREATED             SIZE
oracentos            8                   cd067ed5ce22        36 seconds ago      237MB
2233466866/centos8   latest              a2f2e369e78e        6 months ago        237MB
centos               8                   a2f2e369e78e        6 months ago        237MB

2. Create based on local template

Mirror can be generated by importing the system template file. The template can be downloaded from the OPENVZ open source project. The
address is: https://wiki.openvz.org/Download/template/precreated
or using wget to download: wget http://download.openvz.org/ template/precreated/debian-7.0-x86-minimal.tar.gz

I have a centos8 mirror under /opt

[root@5centos opt]# ls
centos8  containerd  rh
[root@5centos opt]# cat centos8 |docker import - os8:cent
sha256:9997abab01f04c169446e89555a155bd36f040f261134a1740c78a794cba9e3e
[root@5centos opt]# docker images
REPOSITORY           TAG                 IMAGE ID            CREATED             SIZE
os8                  cent                9997abab01f0        22 seconds ago      245MB
oracentos            8                   cd067ed5ce22        8 minutes ago       237MB
2233466866/centos8   latest              a2f2e369e78e        6 months ago        237MB
centos               8                   a2f2e369e78e        6 months ago

Three, create based on Dockerfile

Use Dockerfile to create a httpd image and run it (not for anything else, just because apahce's httpd is easy to install)
Dockerfile is a file composed of a set of instructions. The
Dockerfile structure is divided into four parts:

Basic image information
Maintainer information
Mirror operation instructions
Specify instructions when the container starts

[root@5centos opt]# mkdir /apache
[root@5centos opt]# cd /apache
[root@5centos apache]# vim Dockerfile
FROM centos:8	##基于的基础镜像
MAINTAIER Ora <CN-Ora>	##维护人员信息
RUN yum -y update	##升级所有包同时也升级软件和系统bai内核du
RUN yum -y install httpd	##安装httpd
EXPOSE 80	##开启内部端口80
ADD index.html /var/www/html/index.html	##导入文件
ADD run.sh /run.sh	##同上
RUN chmod +x /run.sh	##加权
CMD ["/run.sh"]		##启动容器时启动脚本

[root@5centos apache]# echo "<h1>This is Ora's Web</h1>" > index.html
[root@5centos apache]# vim run.sh
#!/bin/bash
rm -rf /run/httpd/*		##清除容器内的httpd启动
exec /usr/sbin/apachectl -D FOREGROUND	##启动apache
[root@5centos apache]# ls
Dockerfile  index.html  run.sh
[root@5centos apache]# docker build -t httpd:centos .	##创建镜像，记得空格点
Sending build context to Docker daemon  4.096kB
Step 1/9 : FROM centos:8
 ---> a2f2e369e78e
Step 2/9 : MAINTAINER Ora <CN-Ora>
 ---> Running in dff28da90a0d
Removing intermediate container dff28da90a0d
 ---> 438c17c20473
Step 3/9 : RUN yum -y update
 ---> Running in bff3e9d792f1
 ……省略部分……
 Successfully tagged httpd:centos

View mirror

[root@5centos apache]# docker images
REPOSITORY           TAG                 IMAGE ID            CREATED             SIZE
httpd                centos              6b85ffdb4c45        23 seconds ago      616MB

Run this image

[root@5centos apache]# docker run -d -p 1080:80 httpd:centos	##-p 指定端口号，-P 随机端口号'
a84372f77bc29944addfc436ea6246e399d72d1de123272e759bb04256d6790c
[root@5centos apache]# docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                  NAMES
a84372f77bc2        httpd:centos        "/run.sh"           36 seconds ago      Up 34 seconds       0.0.0.0:1080->80/tcp   keen_hellman

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Docker builds a private warehouse

Private warehouse setup steps

Download the registry image
The client sets the daemon.json file and specifies the location of the private warehouse
Generate registry container and open port 5000
Mirror tagging
Upload image, docker push
Download the image, docker pull

Download the registry image

[root@5centos /]# docker pull registry
Using default tag: latest
latest: Pulling from library/registry
cbdbe7a5bc2a: Pull complete 
47112e65547d: Pull complete 
46bcb632e506: Pull complete 
c1cc712bcecd: Pull complete 
3db6272dcbfa: Pull complete 
Digest: sha256:8be26f81ffea54106bae012c6f349df70f4d5e7e2ec01b143c46e2c03b9e551d
Status: Downloaded newer image for registry:latest
docker.io/library/registry:latest

The client sets the daemon.json file and specifies the location of the private warehouse

[root@5centos /]# vim /etc/docker/daemon.json
{
    
    
  "insecure-registries": ["20.0.0.5:5000"],	##切记逗号别忘了，registry默认端口为5000
  "registry-mirrors": ["https://xh6uo4bd.mirror.aliyuncs.com"]
}
[root@5centos /]# systemctl restart docker

Generate registry container and open port 5000

[root@5centos /]# docker create -it registry /bin/bash
4485837c9052ccc202b343d15ad92dcce29018c842639b80389fde7d5c4697d9
[root@5centos /]# docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                        PORTS               NAMES
4485837c9052        registry            "/entrypoint.sh /bin…"   4 seconds ago       Created                                           optimistic_gould
a84372f77bc2        httpd:centos        "/run.sh"                12 minutes ago      Exited (137) 50 seconds ago                       keen_hellman
[root@5centos /]# docker run -d -p 5000:5000 -v /opt:/opt registry
447a57de666748033cc1155e5e76bc4dff9c4c674e0dbcfa8da02aa5b5681a1f

Mirror tagging

[root@5centos /]# docker tag httpd:centos 20.0.0.5:5000/httpd
[root@5centos /]# docker images
REPOSITORY            TAG                 IMAGE ID            CREATED             SIZE
20.0.0.5:5000/httpd   latest              6b85ffdb4c45        16 minutes ago      616MB
httpd                 centos              6b85ffdb4c45        16 minutes ago      616MB
registry              latest              2d4f4b5309b1        3 months ago        26.2MB

Upload image

[root@5centos /]# docker push 20.0.0.5:5000/httpd 
The push refers to repository [20.0.0.5:5000/httpd]
61e6c1eb3010: Pushed 
4f96d076e862: Pushed 
d9d346bd3bd3: Pushed 
51693b2732fd: Pushed 
3909c87a602a: Pushed 
2f00c0cf81bb: Pushed 
0683de282177: Pushed 
latest: digest: sha256:f7cbad7005013d3ef1958c86bf7c11f83ddb465f4a7ab922cc6827bbf0b66d44 size: 1783
[root@5centos /]#

Download mirror test

[root@5centos /]# curl -XGET http://20.0.0.5:5000/v2/_catalog
{
    
    "repositories":["httpd"]}	##获取私有库镜像列表
[root@5centos /]# docker pull 20.0.0.5:5000/httpd
Using default tag: latest
latest: Pulling from httpd
Digest: sha256:f7cbad7005013d3ef1958c86bf7c11f83ddb465f4a7ab922cc6827bbf0b66d44
Status: Image is up to date for 20.0.0.5:5000/httpd:latest
20.0.0.5:5000/httpd:latest

Docker basic commands + container image