Docker自学笔记 (一)

Docker

https://docs.docker.com 文档

https://hub.docker.com 仓库

docker基本组成

镜像（image）

docker镜像是哟个模板，可以通过这个模板来创建容器服务

容器（container）

docker利用容器技术，独立运行一个或一个组应用，通过镜像来创建

启动、停止、删除

docker是个简易linux系统

仓库（repository）

仓库是放镜像的地方、

仓库分为公有仓库和私有仓库，docker hub 默认是国外的仓库

安装

环境查看

[root@localhost /]# cat /etc/redhat-release
CentOS Linux release 8.5.2111
[root@localhost /]# cat /etc/os-release
NAME="CentOS Linux"
VERSION="8"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="8"
PLATFORM_ID="platform:el8"
PRETTY_NAME="CentOS Linux 8"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:8"
HOME_URL="https://centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"
CENTOS_MANTISBT_PROJECT="CentOS-8"
CENTOS_MANTISBT_PROJECT_VERSION="8"
[root@localhost /]#

帮助文档

#1、卸载旧版本
yum remove docker \
                  docker-client \
                  docker-client-latest \
                  docker-common \
                  docker-latest \
                  docker-latest-logrotate \
                  docker-logrotate \
                  docker-engine
#2、需要安装的包                
sudo yum install -y yum-utils

#3、设置镜像仓库
sudo yum-config-manager \
    --add-repo \
    https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo   #阿里云推荐 \
    https://download.docker.com/linux/centos/docker-ce.repo  #默认是国外的
#4、安装docker相关  docker-ce 社区   ee 企业版 
yum install docker-ce docker-ce-cli containerd.io

#5、启动daocker
systemctl start docker

#6、使用docker version 检测安装
[root@localhost /]# docker version
Client: Docker Engine - Community
 Version:           20.10.14
 API version:       1.41
 Go version:        go1.16.15
 Git commit:        a224086
 Built:             Thu Mar 24 01:47:44 2022
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.14
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.16.15
  Git commit:       87a90dc
  Built:            Thu Mar 24 01:46:10 2022
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.5.11
  GitCommit:        3df54a852345ae127d1fa3092b95168e4a88e2f8
 runc:
  Version:          1.0.3
  GitCommit:        v1.0.3-0-gf46b6ba
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0
[root@localhost /]#

#7、运行 hello world
 sudo docker run hello-world

#8、查看下载hello world 的image
[root@localhost /]# docker images
REPOSITORY               TAG       IMAGE ID       CREATED        SIZE
docker/getting-started   latest    bd9a9f733898   7 weeks ago    28.8MB
hello-world              latest    feb5d9fea6a5   6 months ago   13.3kB
#9、卸载
卸载依赖
yum remove docker-ce docker-ce-cli containerd.io
删除资源
rm -rf /var/lib/docker  #默认工作路径
rm -rf /var/lib/containerd

阿里云镜像加速

(3条消息) docker配置阿里云镜像加速器_奕奕星空的博客-优快云博客_云加速器

#报错 可以重启系统

底层原理

docker是怎么工作的？

Docker 是C/S结构系统，docker 的守护进程运行在主机上。通过Socket从客户端的访问，Server端接收到Docker-Client的指令，就回去执行这个命令。

Docker为什么比VM块？

1、Docker有着比虚拟机更少的抽象层。

2、docker 利用的是宿主机的内核。vm需要的guest os。

Docker常用命令

https://docs.docker.com/engine/reference/commandlin #文档

帮助命令

docker version #显示版本信息
docker info    #显示docker的系统信息。包括镜像和容器数量
docker 命令 --help  #帮助命令

镜像命令

docker images 查询本地镜像

docker images [OPTIONS] [REPOSITORY[:TAG]]  #查看所有本地主机上的镜像

[root@localhost /]# docker images
REPOSITORY               TAG       IMAGE ID       CREATED        SIZE
hello-world              latest    feb5d9fea6a5   6 months ago   13.3kB
#解释
REPOSITORY	镜像的仓库源
TAG       	镜像的标签
MAGE ID   	镜像的ID
CREATED     镜像的创建时间   
SIZE		镜像的大小

#可选项

Options:
  -a, --all            #列出所有镜像
  -q, --quiet           #只显示ID

docker search 搜索镜像

 docker search [OPTIONS] TERM  #搜索镜像
 #可选项，通过搜索来过滤
 --filter=STARS=3000

docker pull 下载镜像

docker pull 镜像名[:tag]   #下载镜像

[root@localhost docker]# docker pull centos
Using default tag: latest    # 默认使用最新的 
latest: Pulling from library/centos


[root@localhost docker]# docker pull mysql:5.7
5.7: Pulling from library/mysql   # 下载源
72a69066d2fe: Pull complete		  #分层下载	
93619dbc5b36: Pull complete
99da31dd6142: Pull complete
626033c43d70: Pull complete
37d5d7efb64e: Pull complete
ac563158d721: Pull complete
d2ba16033dad: Pull complete
0ceb82207cd7: Pull complete
37f2405cae96: Pull complete
e2482e017e53: Pull complete
70deed891d42: Pull complete
Digest: sha256:f2ad209efe9c67104167fc609cca6973c8422939491c9345270175a300419f94  #签名
Status: Downloaded newer image for mysql:5.7
docker.io/library/mysql:5.7  #真实地址
#等价命令
docker pull mysql：5.7
docker pull docker.io/library/mysql:5.7

Options:
  -a, --all-tags                Download all tagged images in the repository
      --disable-content-trust   Skip image verification (default true)
      --platform string         Set platform if server is multi-platform capable
  -q, --quiet                   Suppress verbose output
[root@localhost /]#

docker rmi 删除镜像

docker rmi [OPTIONS] IMAGE_ID  IMAGE_ID  ……
  -f, --force      Force removal of the image
      --no-prune   Do not delete untagged parents
      
[root@localhost ~]# docker rmi -f feb5d9fea6a5  # 删除指定镜像
     
[root@localhost ~]#docker rmi -f $(docker images -qa)   #删除全部镜像

容器命令

说明:有镜像才可以创建容器

docker pull centos

新建容器并启动

docker run [可选参数] image_id
#参数说明
--name="Name"	容器名字 nginx1、nginx2
-d				后台运行方式
-it				使用交互方式运行，进入容器查看内容
-p				指定容器的端口 -p 8080:8080
	-o ip：主机端口：容器端口
	-p 主机端口：容器端口（常用）
	-p 容器端口
	容器端口
-p				随机端口




#测试 启动并进入容器

[root@localhost docker]# docker run -it centos /bin/bash
[root@84ead1d9d6e0 /]# ls  #基础版本 很多命令不完善
bin  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  run  sbin 
[root@84ead1d9d6e0 /]#exit #退出

列出运行的容器

[root@localhost /]# docker ps    # 列出当前运行的容器
CONTAINER ID   IMAGE     COMMAND   CREATED   STATUS    PORTS     NAMES
[root@localhost /]# docker ps -a # 列出历史运行的容器
CONTAINER ID   IMAGE     COMMAND       CREATED         STATUS                          PORTS     NAMES
84ead1d9d6e0   centos    "/bin/bash"   2 minutes ago   Exited (0) About a minute ago             heuristic_rubin
[root@localhost /]# docker ps -n=1 #列出最近创建的容器
CONTAINER ID   IMAGE     COMMAND       CREATED         STATUS                     PORTS     NAMES
84ead1d9d6e0   centos    "/bin/bash"   9 minutes ago   Exited (0) 7 minutes ago             heuristic_rubin
[root@localhost /]# docker ps -aq  #只显示镜像ID
84ead1d9d6e0

退出容器

exit #直接退出停止容器
Ctrl + P + Q #容器不停止退出

删除容器

docker rm 容器ID				#删除指定容器
docker rm -f $(docker ps -aq)	 #删除所有容器	
docker ps -aq | xargs docker rm

启动和停止

docker start 容器ID
docker restart 容器ID
docker stop 容器ID
docker kill 容器ID  #强制停止容器

常用的其他命令

后台启动命令

#命令 docker run -d images
[root@localhost /]# docker run -d centos
#问题docker ps ，发现 centos 停止了
#常见的坑：docker 容器使用后台云心，就必须有一个前台进程，docker 发现没有前台应用就会自动停止
#nginx 容器启动后 发现自己没有提供服务 就会立刻停止

查看日志

docker logs -t -f --tail 容器ID

#脚本
[root@localhost /]docker run -d centos /bin/bash -c "while true;do ping baidu.com;done"
[root@localhost /]# docker ps
CONTAINER ID   IMAGE     COMMAND                  CREATED          STATUS          PORTS     NAMES
39b952d20d33   centos    "/bin/bash -c 'while…"   12 minutes ago   Up 12 minutes             lucid_sanderson
#-tf 显示日志
 --tail 显示条数
[root@localhost /]docker logs -tf --tail 10 39b952d20d33 

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查看容器的进程信息

#docker top 容器ID
[root@localhost /]# docker top 39b952d20d33
UID       PID        PPID      C       STIME    TTY     TIME     CMD
root     38940    38920    0       02:21    ?       00:00:00  /bin/bash -c while true;do 
root     38967    38940    0       02:21    ?       00:00:00  ping baidu.com

查看镜像的源数据

#命令
docker inspect 容器ID
[root@localhost ~]# docker inspect --help

Usage:  docker inspect [OPTIONS] NAME|ID [NAME|ID...]

Return low-level information on Docker objects

Options:
  -f, --format string   Format the output using the given Go template
  -s, --size            Display total file sizes if the type is container
      --type string     Return JSON for specified type
      
[root@localhost ~]# docker inspect 39b952d20d33
[
    {
        "Id": "39b952d20d33c9671a6fcad9748c1ee93c0b01cd6ac7b578baff1ecc76fda278",
        "Created": "2022-04-05T18:21:04.893070851Z",
        "Path": "/bin/bash",
        "Args": [
            "-c",
            "while true;do ping baidu.com;done"
        ],
        "State": {
            "Status": "running",
            "Running": true,
            "Paused": false,
            "Restarting": false,
            "OOMKilled": false,
            "Dead": false,
            "Pid": 38940,
            "ExitCode": 0,
            "Error": "",
            "StartedAt": "2022-04-05T18:21:05.429467757Z",
            "FinishedAt": "0001-01-01T00:00:00Z"
        },
        "Image": "sha256:5d0da3dc976460b72c77d94c8a1ad043720b0416bfc16c52c45d4847e53fadb6",
        "ResolvConfPath": "/var/lib/docker/containers/39b952d20d33c9671a6fcad9748c1ee93c0b01cd6ac7b578baff1ecc76fda278/resolv.conf",
        "HostnamePath": "/var/lib/docker/containers/39b952d20d33c9671a6fcad9748c1ee93c0b01cd6ac7b578baff1ecc76fda278/hostname",
        "HostsPath": "/var/lib/docker/containers/39b952d20d33c9671a6fcad9748c1ee93c0b01cd6ac7b578baff1ecc76fda278/hosts",
        "LogPath": "/var/lib/docker/containers/39b952d20d33c9671a6fcad9748c1ee93c0b01cd6ac7b578baff1ecc76fda278/39b952d20d33c9671a6fcad9748c1ee93c0b01cd6ac7b578baff1ecc76fda278-json.log",
        "Name": "/lucid_sanderson",
        "RestartCount": 0,
        "Driver": "overlay2",
        "Platform": "linux",
        "MountLabel": "",
        "ProcessLabel": "",
        "AppArmorProfile": "",
        "ExecIDs": null,
        "HostConfig": {
            "Binds": null,
            "ContainerIDFile": "",
            "LogConfig": {
                "Type": "json-file",
                "Config": {}
            },
            "NetworkMode": "default",
            "PortBindings": {},
            "RestartPolicy": {
                "Name": "no",
                "MaximumRetryCount": 0
            },
            "AutoRemove": false,
            "VolumeDriver": "",
            "VolumesFrom": null,
            "CapAdd": null,
            "CapDrop": null,
            "CgroupnsMode": "host",
            "Dns": [],
            "DnsOptions": [],
            "DnsSearch": [],
            "ExtraHosts": null,
            "GroupAdd": null,
            "IpcMode": "private",
            "Cgroup": "",
            "Links": null,
            "OomScoreAdj": 0,
            "PidMode": "",
            "Privileged": false,
            "PublishAllPorts": false,
            "ReadonlyRootfs": false,
            "SecurityOpt": null,
            "UTSMode": "",
            "UsernsMode": "",
            "ShmSize": 67108864,
            "Runtime": "runc",
            "ConsoleSize": [
                0,
                0
            ],
            "Isolation": "",
            "CpuShares": 0,
            "Memory": 0,
            "NanoCpus": 0,
            "CgroupParent": "",
            "BlkioWeight": 0,
            "BlkioWeightDevice": [],
            "BlkioDeviceReadBps": null,
            "BlkioDeviceWriteBps": null,
            "BlkioDeviceReadIOps": null,
            "BlkioDeviceWriteIOps": null,
            "CpuPeriod": 0,
            "CpuQuota": 0,
            "CpuRealtimePeriod": 0,
            "CpuRealtimeRuntime": 0,
            "CpusetCpus": "",
            "CpusetMems": "",
            "Devices": [],
            "DeviceCgroupRules": null,
            "DeviceRequests": null,
            "KernelMemory": 0,
            "KernelMemoryTCP": 0,
            "MemoryReservation": 0,
            "MemorySwap": 0,
            "MemorySwappiness": null,
            "OomKillDisable": false,
            "PidsLimit": null,
            "Ulimits": null,
            "CpuCount": 0,
            "CpuPercent": 0,
            "IOMaximumIOps": 0,
            "IOMaximumBandwidth": 0,
            "MaskedPaths": [
                "/proc/asound",
                "/proc/acpi",
                "/proc/kcore",
                "/proc/keys",
                "/proc/latency_stats",
                "/proc/timer_list",
                "/proc/timer_stats",
                "/proc/sched_debug",
                "/proc/scsi",
                "/sys/firmware"
            ],
            "ReadonlyPaths": [
                "/proc/bus",
                "/proc/fs",
                "/proc/irq",
                "/proc/sys",
                "/proc/sysrq-trigger"
            ]
        },
        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/40a0f78a2b1de997b3f2af1897968b372fe6594c8236c33e091b8c5537c5c64b-init/diff:/var/lib/docker/overlay2/1fb6cbbaf813f00194bdb7ae04422e7aa31753a3ebe91d9f5f88fa54a04c2e16/diff",
                "MergedDir": "/var/lib/docker/overlay2/40a0f78a2b1de997b3f2af1897968b372fe6594c8236c33e091b8c5537c5c64b/merged",
                "UpperDir": "/var/lib/docker/overlay2/40a0f78a2b1de997b3f2af1897968b372fe6594c8236c33e091b8c5537c5c64b/diff",
                "WorkDir": "/var/lib/docker/overlay2/40a0f78a2b1de997b3f2af1897968b372fe6594c8236c33e091b8c5537c5c64b/work"
            },
            "Name": "overlay2"
        },
        "Mounts": [],
        "Config": {
            "Hostname": "39b952d20d33",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/bash",
                "-c",
                "while true;do ping baidu.com;done"
            ],
            "Image": "centos",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": {
                "org.label-schema.build-date": "20210915",
                "org.label-schema.license": "GPLv2",
                "org.label-schema.name": "CentOS Base Image",
                "org.label-schema.schema-version": "1.0",
                "org.label-schema.vendor": "CentOS"
            }
        },
        "NetworkSettings": {
            "Bridge": "",
            "SandboxID": "f0f4e4d7c22cad51c1f6bbcc455a42ece6d208551c61587ac00c553d3e58a339",
            "HairpinMode": false,
            "LinkLocalIPv6Address": "",
            "LinkLocalIPv6PrefixLen": 0,
            "Ports": {},
            "SandboxKey": "/var/run/docker/netns/f0f4e4d7c22c",
            "SecondaryIPAddresses": null,
            "SecondaryIPv6Addresses": null,
            "EndpointID": "0b799b7071838712d21071d6245983e02709a8d727f6577979ec0f230893b361",
            "Gateway": "172.17.0.1",
            "GlobalIPv6Address": "",
            "GlobalIPv6PrefixLen": 0,
            "IPAddress": "172.17.0.2",
            "IPPrefixLen": 16,
            "IPv6Gateway": "",
            "MacAddress": "02:42:ac:11:00:02",
            "Networks": {
                "bridge": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": null,
                    "NetworkID": "19eebba27026f51f10a5240fdcdc81de5f96d51abcf6035b543b3ce574d2c8c9",
                    "EndpointID": "0b799b7071838712d21071d6245983e02709a8d727f6577979ec0f230893b361",
                    "Gateway": "172.17.0.1",
                    "IPAddress": "172.17.0.2",
                    "IPPrefixLen": 16,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "MacAddress": "02:42:ac:11:00:02",
                    "DriverOpts": null
                }
            }
        }
    }
]

进入当前运行的容器

#进入后台的运行的容器

#命令
docker exec -it 39b952d20d33  bashShell
[root@localhost ~]# docker ps
CONTAINER ID   IMAGE     COMMAND                  CREATED             STATUS             PORTS     NAMES
39b952d20d33   centos    "/bin/bash -c 'while…"   About an hour ago   Up About an hour      [root@localhost ~]# docker exec -it 39b952d20d33 /bin/bash

#docker attach 容器ID
#测试
[root@localhost ~]# docker attach 39b952d20d33
From 39b952d20d33 (172.17.0.2) icmp_seq=3680 Destination Host Unreachable


#docker exec # 进入容器后开启一个终端
#docker attach #进入容器当前运行的终端

从容器拷贝文件到宿主机

docker cp 容器id：容器路径 

#在容器内新建文件
[root@0372e62cc26f /]# touch dockercp.txt
[root@0372e62cc26f /]# ls
bin  dockercp.txt  home  lib64       media  opt   root  sbin  sys  usr
dev  etc           lib   lost+found  mnt    proc  run   srv   tmp  var
[root@0372e62cc26f /]# docker cp 0372e62cc26f /dockercp.txt /root

#将容器内的文件拷贝出来
[root@localhost ~]# docker cp 0372e62cc26f:/dockercp.txt /root
[root@localhost ~]# ls
anaconda-ks.cfg  dockercp.txt  ll  test  test1  testdir  testdirln  testln  testln1
[root@localhost ~]#

小结

练习

安装nginx

在仓库搜索镜像

下载镜像

[root@localhost ~]# docker pull nginx
Using default tag: latest
latest: Pulling from library/nginx
a2abf6c4d29d: Pull complete
a9edb18cadd1: Pull complete
589b7251471a: Pull complete
186b1aaa4aa6: Pull complete
b4df32aa5a72: Pull complete
a0bcbecc962e: Pull complete
Digest: sha256:0d17b565c37bcbd895e9d92315a05c1c3c9a29f762b011a10c54a66cd53c9b31
Status: Downloaded newer image for nginx:latest
docker.io/library/nginx:latest
[root@localhost ~]#

运行镜像

docker run -d --name nginx01 -p 3344:80 nginx
e1207663d7cecb3090bd35debcad2d47a5d0a54c1f6a2d441700ba2bba4135ec

验证

[root@localhost ~]# curl localhost:3344
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

进入容器

[root@localhost ~]# docker exec -it e1207663d7ce  /bin/bash
root@e1207663d7ce:/#

安装tomcat

 #官方使用
 docker run -it --rm tomcat:9.0
 #用完即删除
 
 #下载
 docker pull tomcat
 
 #启动运行
docker run -d -p 3355:8080 --name tomcat01 tomcat

#进入容器
[root@localhost ~]# docker exec -it tomcat01 /bin/bash
#linux 命令缺少  没有站点 

#复制站点
root@139163325a5a:/usr/local/tomcat# cp -r webapps.dist/* webapps

安装ES+kibana

#ES暴露端口多、占用资源多、数据单独挂载、

docker run -d --name elasticsearch -p 9200:9200 -p 9300:9300 -e "discovery.type=single-node" elasticsearch:8.1.2

#启动之后 Linux 非常卡
docker stats

#启动之后迅速关闭
docker stop e927e55d379c

#验证
[root@localhost ~]# curl localhost:9200
{
  "name" : "fHjbm--",
  "cluster_name" : "elasticsearch",
  "cluster_uuid" : "kaCC5NXXTEKq87wd6TRJlQ",
  "version" : {
    "number" : "5.6.12",
    "build_hash" : "cfe3d9f",
    "build_date" : "2018-09-10T20:12:43.732Z",
    "build_snapshot" : false,
    "lucene_version" : "6.6.1"
  },
  "tagline" : "You Know, for Search"
}


[root@localhost ~]# docker stats
CONTAINER ID   NAME            CPU %     MEM USAGE / LIMIT     MEM %     NET I/O        BLOCK I/O        PIDS
e927e55d379c   elasticsearch   0.11%     1.209GiB / 1.748GiB   69.17%    1.5kB / 729B   769MB / 49.2kB   39

#-e 配置使用的内存
docker run -d --name elasticsearch -p 9200:9200 -p 9300:9300 -e "discovery.type=single-node" -e ES_JAVA_OPTS="-Xms64m -Xmx512M" elasticsearch


CONTAINER ID   NAME              CPU %     MEM USAGE / LIMIT     MEM %     NET I/O     BLOCK I/O        PIDS
2bac80f883af   elasticsearch02   0.23%     244.1MiB / 1.748GiB   13.63%    766B / 0B   144MB / 67.6kB   36

[root@localhost ~]# curl localhost:9200
{
  "name" : "ZS50Q_Z",
  "cluster_name" : "elasticsearch",
  "cluster_uuid" : "acXTAtDESFSxl2eA2ok1QA",
  "version" : {
    "number" : "5.6.12",
    "build_hash" : "cfe3d9f",
    "build_date" : "2018-09-10T20:12:43.732Z",
    "build_snapshot" : false,
    "lucene_version" : "6.6.1"
  },
  "tagline" : "You Know, for Search"
}
[root@localhost ~]#

ikbana如何连接docker

可视化

Install Portainer with Docker on Linux - Portainer Documentation 文档

#安装
docker run -d -p 8088:9000 --restart=always -v  /var/run/docker.sock:/var/run/docker.sock  --privileged=true portainer/portainer

http://192.168.0.16:8088/#/init/admin

Docker 镜像讲解

镜像是什么

是一种轻量级、可执行的独立软件包，用来打包软件运行环境和基于运行环境开发的软件，它包台运行某个软件所需的所有内容，包括代码、运行时、库、环变量和配置文件
所有的应用，直接打包docker镜像，就可以直接跑起来！

如何获得镜像

• 从远程仓库下载
• 朋友拷贝
• 自己制作一个镜像dockerfile

Docker镜像加载原理

UnionFS（联合文件系统〕

UnionFS（联合文件系统）：Union文件系统（UnionFS)是一种分层、轻量级并且高性能的文件系统，它支持对文件系统的修改作为一次提交来一层层的叠加，同时可以将不同目录挂载到同一个拟文件系统下（unite several directories into a single virtual filesystem)。Union文件系统是Docker镜像的基础。镜像可以通过分层来讲行继承，基于基础镜像（没有父像），可以制作各种具体的应用镜像。
特性：一次同时加载多个文件系统，但从外面看起来，只能看到一文件系统，联合加载会巴各层文件系统叠加起来，这样最终的文件系统会包含所有底层的文件和目录

Docker镜像加载原理

docker的镜像实际上由一层一层的文件系统组成，这种层级的文件系统UnionFS。
bootfs(bootfilesystem)主要包含bootloader和kernel,bootloaderæ要是引导Linux刚启动时会加载bootfs文件系
统，在Docker镜像的最底层是bootfso这一层与我们典型的Linux/Unix系统是一样的，包含boot加载器和内核。当boot加载完成之后整个内核就都在内存中了，此时内存的使用权已由bootfs转交给内核，此时系统也会卸载bootfs。
rootfs(rootfilesystem)，在bootfs之上。包含的就是典型Linux系统中的/dev,/proc,/bin,/etc等标准目录和文件。rootfs就是各种不同的操作系统发行版，比如Ubuntu，centos等等。

分层理解

[root@localhost ~]# docker pull redis
Using default tag: latest
latest: Pulling from library/redis
a2abf6c4d29d: Already exists
c7a4e4382001: Pull complete
4044b9ba67c9: Pull complete
c8388a79482f: Pull complete
413c8bb60be2: Pull complete
1abfd3011519: Pull complete
Digest: sha256:db485f2e245b5b3329fdc7eff4eb00f913e09d8feb9ca720788059fdc2ed8339
Status: Downloaded newer image for redis:latest
docker.io/library/redis:latest
[root@localhost ~]#

思考：为什么Docker镜像要采用这种分层的结构呢？
最大的好处，我觉得莫过于是资源共享了！比如有多个境像都从相同的Base源像构建而来，宿主机只需在磁盘上保留一份base像，同时内存中也只需要载一份b醑e像，这样就可以为所有的容器服务了，而目漳像的每一层都可以被共享。点看镜像分层的方式可以通过docker image inspect命令！

[root@localhost ~]# docker inspect redis:latest
[
    {
        "Id": "sha256:7614ae9453d1d87e740a2056257a6de7135c84037c367e1fffa92ae922784631",
        "RepoTags": [
            "redis:latest"
        ],
        "RepoDigests": [
            "redis@sha256:db485f2e245b5b3329fdc7eff4eb00f913e09d8feb9ca720788059fdc2ed8339"
        ],
        "Parent": "",
        "Comment": "",
        "Created": "2021-12-21T12:42:49.755107412Z",
        "Container": "13d25f53410417c5220c8dfe8bd49f06abdbcd69faa62a9b877de02464bb04a3",
        "ContainerConfig": {
            "Hostname": "13d25f534104",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "ExposedPorts": {
                "6379/tcp": {}
            },
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "GOSU_VERSION=1.12",
                "REDIS_VERSION=6.2.6",
                "REDIS_DOWNLOAD_URL=http://download.redis.io/releases/redis-6.2.6.tar.gz",
                "REDIS_DOWNLOAD_SHA=5b2b8b7a50111ef395bf1c1d5be11e6e167ac018125055daa8b5c2317ae131ab"
            ],
            "Cmd": [
                "/bin/sh",
                "-c",
                "#(nop) ",
                "CMD [\"redis-server\"]"
            ],
            "Image": "sha256:e093f59d716c95cfce82c676f099b960cc700432ab531388fcedf79932fc81ec",
            "Volumes": {
                "/data": {}
            },
            "WorkingDir": "/data",
            "Entrypoint": [
                "docker-entrypoint.sh"
            ],
            "OnBuild": null,
            "Labels": {}
        },
        "DockerVersion": "20.10.7",
        "Author": "",
        "Config": {
            "Hostname": "",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "ExposedPorts": {
                "6379/tcp": {}
            },
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "GOSU_VERSION=1.12",
                "REDIS_VERSION=6.2.6",
                "REDIS_DOWNLOAD_URL=http://download.redis.io/releases/redis-6.2.6.tar.gz",
                "REDIS_DOWNLOAD_SHA=5b2b8b7a50111ef395bf1c1d5be11e6e167ac018125055daa8b5c2317ae131ab"
            ],
            "Cmd": [
                "redis-server"
            ],
            "Image": "sha256:e093f59d716c95cfce82c676f099b960cc700432ab531388fcedf79932fc81ec",
            "Volumes": {
                "/data": {}
            },
            "WorkingDir": "/data",
            "Entrypoint": [
                "docker-entrypoint.sh"
            ],
            "OnBuild": null,
            "Labels": null
        },
        "Architecture": "amd64",
        "Os": "linux",
        "Size": 112691373,
        "VirtualSize": 112691373,
        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/b94e3e76fe43e5b189d59382a1ca370bec538d1a0dea10e3b031a4bf9c4c57c1/diff:/var/lib/docker/overlay2/351c8e053f1467ef695036aefc82871a6bf3a9dc0c97b480aab6fdd06750f6ed/diff:/var/lib/docker/overlay2/ffe7db0d850a2c19799407fa06000e48e3856775840c21d427fbbc1688b8a4e7/diff:/var/lib/docker/overlay2/1aaf52a048a5b7731782f464e980d83ec1caa9010fc5289e572edab5ea00365b/diff:/var/lib/docker/overlay2/3a015bf48294c76365caf543e0470eede7d47c151551af6714519d2b282bb976/diff",
                "MergedDir": "/var/lib/docker/overlay2/8e7f70fc7b48c75a391cd5887f4dbd61584ca25f8184de36a6385f0b1d96f1a9/merged",
                "UpperDir": "/var/lib/docker/overlay2/8e7f70fc7b48c75a391cd5887f4dbd61584ca25f8184de36a6385f0b1d96f1a9/diff",
                "WorkDir": "/var/lib/docker/overlay2/8e7f70fc7b48c75a391cd5887f4dbd61584ca25f8184de36a6385f0b1d96f1a9/work"
            },
            "Name": "overlay2"
        },
        "RootFS": {
            "Type": "layers",
            "Layers": [
                "sha256:2edcec3590a4ec7f40cf0743c15d78fb39d8326bc029073b41ef9727da6c851f",
                "sha256:9b24afeb7c2f21e50a686ead025823cd2c6e9730c013ca77ad5f115c079b57cb",
                "sha256:4b8e2801e0f956a4220c32e2c8b0a590e6f9bd2420ec65453685246b82766ea1",
                "sha256:529cdb636f61e95ab91a62a51526a84fd7314d6aab0d414040796150b4522372",
                "sha256:9975392591f2777d6bf4d9919ad1b2c9afa12f9a9b4d260f45025ec3cc9b18ed",
                "sha256:8e5669d8329116b8444b9bbb1663dda568ede12d3dbcce950199b582f6e94952"
            ]
        },
        "Metadata": {
            "LastTagTime": "0001-01-01T00:00:00Z"
        }
    }
]
[root@localhost ~]#

特点

docker 镜像都是只读，当容器启动后，一个新的可写层被加载到镜像的顶部！

这一层就是我们通常说的容器层，容器层之下都叫镜像层。

如何提交一个自己的镜像？

Commit 镜像**

docker commit #提交容器成为一个副本
#命令和git原理类似
docker cimmit -m="提交描述信息" -a="作者" 容器ID 目标镜像名：[TAG]

练习

#启动一个默认的tomcat 

#默认的webapps 没有文件

#拷贝文件

#将修改后的容器通过commit 提交为一个镜像

[root@localhost ~]# docker commit -a="lxf" -m="add web app"  5b07255721fa tomcat02:1.0
sha256:aff84909b34e9948fa6c0ef61871d0e200a1b465176b82151953ca78376086ff
[root@localhost ~]# docker images
REPOSITORY            TAG       IMAGE ID       CREATED          SIZE
tomcat02              1.0       aff84909b34e   11 seconds ago   684MB
nginx                 latest    605c77e624dd   3 months ago     141MB
tomcat                9.0       b8e65a4d736d   3 months ago     680MB
tomcat                latest    fb5657adc892   3 months ago     680MB
redis                 latest    7614ae9453d1   3 months ago     113MB
mysql                 5.7       c20987f18b13   3 months ago     448MB
centos                latest    5d0da3dc9764   6 months ago     231MB
portainer/portainer   latest    580c0e4e98b0   12 months ago    79.1MB
elasticsearch         latest    5acf0e8da90b   3 years ago      486MB
[root@localhost ~]#
docker commit -a="lxf" -m="add web app"  5b07255721fa tomcat02:1.0