Simply put, a template image is read-only container used to create a container.
When running the container needs to specify the mirror, the mirror if not locally are downloaded from Docker Registry. The default is looking Docker Hub. (Docker Hub is the official public warehouse)
Docker is a mirror image of the incremental changes, each time you create a new image will build an incremental layer in the old mirror above, the use of the technology is Another Union File System (AUFS).
For example, a mirror ubuntu name: 14.04, ubuntu before the colon is the name of the warehouse, the latter is 14.04 TAG, TAG may correspond to the same of different mirror, the version number is usually set to TAG mirror.
If not TAG, then Docker uses the default TAG: latest.
Image management involves the following commands:
A view mirror list
# Management Commands $ Docker image ls + [image name] # The old command format is as follows: $ docker images
For example
[root@TBEARZ206458 ~]# docker image ls REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu latest 72300a873c2c 10 days ago 64.2MB busybox latest 6d5fcfe5ff17 2 months ago 1.22MB hello-world latest fce289e99eb9 14 months ago 1.84kB [root@TBEARZ206458 ~]# docker image ls ubuntu REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu latest 72300a873c2c 10 days ago 64.2MB
Second, to view mirror details
On a document also docker inspect command, it can be used to view information container may also be used to view information in the image (view metadata)
$ docker image inspect ubuntu # The old command format is as follows: $ docker inspect ubuntu
For example
[root@TBEARZ206458 ~]# docker image inspect ubuntu | grep Last
"LastTagTime": "0001-01-01T00:00:00Z"
Third, the image search
$ docker search ubuntu
For example, after the above command is executed
[root@TBEARZ206458 ~]# docker search ubuntu NAME DESCRIPTION STARS OFFICIAL AUTOMATED ubuntu Ubuntu is a Debian-based Linux operating sys… 10575 [OK] dorowu/ubuntu-desktop-lxde-vnc Docker image to provide HTML5 VNC interface … 398 [OK] rastasheep/ubuntu-sshd Dockerized SSH service, built on top of offi… 243 [OK] consol/ubuntu-xfce-vnc Ubuntu container with "headless" VNC session… 211 [OK] ubuntu-upstart Upstart is an event-based replacement for th… 105 [OK] ansible/ubuntu14.04-ansible Ubuntu 14.04 LTS with ansible 98 [OK]
among them:
1 , Official ImagesRF Royalty Free refer docker standard library , a docker establish official .
2 , user-created image will have userid of the prefix.
3 , Automated builds is through code version management site in conjunction with docker hub interface provides generated , for example github, bitbucket,
You need to register docker hub, then use github or bitbucket in accounts linked to the docker hub, and then you can choose to github or bitbucket inside the project automatically build docker image, so long as the code version management site of the project is updated , it will trigger automatically create image.
Fourth, the mirror pulling
Registry in order to obtain a mirror or warehouse
# Management Commands $ docker image pull [OPTIONS] NAME[:TAG|@DIGEST] # The old command format is as follows: $ docker pull [OPTIONS] NAME[:TAG|@DIGEST]
More commonly used configuration parameters -a , mirror on behalf of all downloads in the warehouse, which download the entire repository.
Name can specify not only the Tag , can also digest ( DIGEST to pull a different image). We can see the image information
Example: pulling Ubuntu 14.04 version mirror
[root@TBEARZ206458 ~]# docker image pull ubuntu:14.04 14.04: Pulling from library/ubuntu 2e6e20c8e2e6: Pull complete 30bb187ac3fc: Pull complete b7a5bcc4a58a: Pull complete Digest: sha256:ffc76f71dd8be8c9e222d420dc96901a07b61616689a44c7b3ef6a10b7213de4 Status: Downloaded newer image for ubuntu:14.04 docker.io/library/ubuntu:14.04
To pull the mirror down, its default save path / var / lib / Docker . Because there is a storage drive aufs , so the specific path / var / lib / Docker / aufs .
Fifth, build a mirror
对于我们 pull 的新镜像 ubuntu:14.04 来说，如果我们需要对其进行更新，可以创建一个容器，在容器中进行修改，然后将修改提交到一个新的镜像中。
# Management Commands $ docker container commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]] # 旧的命令格式如下： $ docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]
该命令的解释为从一个容器的修改中创建一个新的镜像。例如，我们运行一个容器，然后在其中创建一个文件，最后使用 commit 命令。
举例： 我们创建一个busybox的容器，里面添加两个文件file1和file2，然后将其提交到一个新的镜像中。
[root@TBEARZ206458 ~]# docker container run --name MyNewBusyBox -it busybox /bin/sh / # touch file1 file2
ctrl+p+q 后台运行
检查一下是否创建
[root@TBEARZ206458 ~]# docker container diff MyNewBusyBox A /file1 A /file2 C /root A /root/.ash_history
创建一个新的镜像
[root@TBEARZ206458 ~]# docker container commit MyNewBusyBox busybox busybox:latest hello-world hello-world:latest ubuntu ubuntu:14.04 ubuntu:latest [root@TBEARZ206458 ~]# docker container commit MyNewBusyBox busybox:mynew sha256:9d1d031bfd1efe1adaf7db123c30f974647e165899c3d3fd179df0c0c3a41631 [root@TBEARZ206458 ~]# docker image ls busybox REPOSITORY TAG IMAGE ID CREATED SIZE busybox mynew 9d1d031bfd1e 15 seconds ago 1.22MB busybox latest 6d5fcfe5ff17 2 months ago 1.22MB
通过上述操作我们创建了一个新的镜像，但是本方法不推荐用在生产系统中，未来会很难维护镜像。最好的创建镜像的方法是 Dockerfile，修改镜像的方法是修改 Dockerfile，然后重新从 Dockerfile 中构建新的镜像。
构建 BUILD
docker 可以从一个 Dockerfile 文件中自动读取指令构建一个新的镜像。 Dockerfile 是一个包含用户构建镜像命令的文本文件。
docker image build [OPTIONS] PATH | URL
构建镜像时，该过程的第一件事是将 Dockerfile 文件所在目录下的所有内容递归的发送到守护进程。所以在大多数情况下，最好是创建一个新的目录，在其中保存 Dockerfile，并在其中添加构建 Dockerfile 所需的文件。
DockerFile的基本语法：略
举例：安装一个拥有dotnet core环境的centos，并运行事例代码。
预备工作：先创建一个dotnetCoreweb程序，然后通过FTP上传到Linux服务器上
我是放在了/home/lic/dockerfiledir 文件夹下
[root@TBEARZ206458 dockerfiledir]# ll drwxr-xr-x 3 root root 4096 Mar 4 17:23 DotnetWebDemo
①在该文件夹下创建一个DockerFile
备注：这里我使用的是3.1版本的dotnetcore，注意下镜像的仓库位置，我在试验过程中遇到了版本不一致的问题，主要是拉取的镜像不能支持启动的dotnet程序
It was not possible to find any compatible framework version
如果是1.0-2.x 可以使用 microsoft/aspnetcore 这是镜像仓库地址，从图上也可以看到，这是一个过时的地址。
如果是3.0以上的可以使用下面的地址： https://hub.docker.com/_/microsoft-dotnet-core-aspnet/
FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 MAINTAINER [email protected] # 容器暴露的端口 EXPOSE 5000 # 把当前目录内容拷贝到容器的home目录 COPY . /home # 设置工作目录 WORKDIR /home # 启动程序 ENTRYPOINT ["dotnet", "DotnetWebDemo/DotnetWebDemo.dll"]
② Builde一下镜像，大概过程如下
[root@TBEARZ206458 dockerfiledir]# docker image build -t centosdotnet:1.0.0 . Sending build context to Docker daemon 344.6kB Step 1/6 : FROM docker.io/microsoft/dotnet ---> 56a634b88a04 Step 2/6 : MAINTAINER [email protected] ---> Running in f915b73424fc Removing intermediate container f915b73424fc ---> 690e1fe5200d Step 3/6 : EXPOSE 5000 ---> Running in 8befbf97b8c1 Removing intermediate container 8befbf97b8c1 ---> d50f54877f3b Step 4/6 : COPY . /home ---> 54953a90f171 Step 5/6 : WORKDIR /home ---> Running in ddab8f58d279 Removing intermediate container ddab8f58d279 ---> 7accfc7efc5b Step 6/6 : ENTRYPOINT ["dotnet", "DotnetWebDemo/DotnetWebDemo.dll"] ---> Running in 4a6d400603b2 Removing intermediate container 4a6d400603b2 ---> 12291ac40ff3 Successfully built 12291ac40ff3 Successfully tagged centosdotnet:1.0.0
查看一下镜像
[root@TBEARZ206458 dockerfiledir]# docker image ls -a REPOSITORY TAG IMAGE ID CREATED SIZE centosdotnet 1.0.0 547d7924e8d2 21 minutes ago 208MB <none> <none> b81319ea9700 21 minutes ago 208MB <none> <none> fab8ef06bcba 21 minutes ago 208MB <none> <none> fc5b570e7e66 21 minutes ago 207MB <none> <none> 252cd9849401 21 minutes ago 207MB microsoft/dotnet-nightly latest 437f8c6bee32 37 hours ago 1.74GB busybox mynew 9d1d031bfd1e 3 days ago 1.22MB microsoft/dotnet latest 56a634b88a04 8 days ago 1.74GB mcr.microsoft.com/dotnet/core/aspnet 3.1 e2cd20adb129 8 days ago 207MB ubuntu latest 72300a873c2c 13 days ago 64.2MB centos latest 470671670cac 6 weeks ago 237MB busybox latest 6d5fcfe5ff17 2 months ago 1.22MB ubuntu 14.04 6e4f1fe62ff1 2 months ago 197MB hello-world latest fce289e99eb9 14 months ago 1.84kB microsoft/aspnetcore latest db030c19e94b 18 months ago 347MB
上面的none应该是和centosdotnet镜像一起build之后出现的。
③启动镜像
[root@TBEARZ206458 dockerfiledir]# docker run -it -p 8080:80 centosdotnet:1.0.0
warn: Microsoft.AspNetCore.DataProtection.Repositories.FileSystemXmlRepository[60]
Storing keys in a directory '/root/.aspnet/DataProtection-Keys' that may not be persisted outside of the container. Protected data will be unavailable when container is destroyed.
info: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[0]
User profile is available. Using '/root/.aspnet/DataProtection-Keys' as key repository; keys will not be encrypted at rest.
info: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[58]
Creating key {4cb11721-8b0e-48f9-9749-a17abe7ec075} with creation date 2020-03-06 02:38:36Z, activation date 2020-03-06 02:38:36Z, and expiration date 2020-06-04 02:38:36Z.
warn: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[35]
No XML encryptor configured. Key {4cb11721-8b0e-48f9-9749-a17abe7ec075} may be persisted to storage in unencrypted form.
info: Microsoft.AspNetCore.DataProtection.Repositories.FileSystemXmlRepository[39]
Writing data to file '/root/.aspnet/DataProtection-Keys/key-4cb11721-8b0e-48f9-9749-a17abe7ec075.xml'.
info: Microsoft.Hosting.Lifetime[0]
Now listening on: http://[::]:80
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Production
info: Microsoft.Hosting.Lifetime[0]
Content root path: /home
这里主要是端口问题需要注意一下，一开始我也不理解
使用 -p 参数时，可以指定要映射的端口，并且在一个指定的端口上只可以绑定一个容器。支持的格式有：
1. IP:HostPort:ContainerPort
2. IP:ContainerPort
3. HostPort:ContainerPort
例如： docker run -d -p 8080:80 nginx
本地主机的 8080 端口被映射到了容器的 80 端口，通过localhost:8080就可以访问容器的80的nginx欢迎页面
验证一下上面的操作：访问一些 http://localhost:8080 就返回了一些信息
备注：这里我在部署程序之后，发现了一个问题，就是我 .net 程序能访问通，但是所有的静态文件访问失败了。
此问题的原因：在于刚刚那个DockerFile，里面这两行
# 设置工作目录 WORKDIR /home # 启动程序 ENTRYPOINT ["dotnet", "DotnetWebDemo/DotnetWebDemo.dll"]
本意是在docker的 home目录下 执行 dotnet DotnetWebDemo/DotnetWebDemo.dll 命令 以启动站点，结果是站点的确启动了，但是程序的启动目录也是/home
这时候，实际上我的wwwroot文件夹并不在该目录下面，所以就会报错。
两种解决办法
1.移动wwwroot目录到/home下，重启容器
2.编辑DockerFile，重新打一下镜像，修改工作目录如下：
# 设置工作目录 WORKDIR /home/DotnetWebDemo //这里改一下 # 启动程序 ENTRYPOINT ["dotnet", "DotnetWebDemo.dll"] //这里改一下
六、删除镜像
我们删除 ubuntu:latest 镜像就可以使用如下命令：需要注意的是，如果该镜像正在被一个容器所使用，需要将容器删除才能成功的删除镜像。
# Management Commands $ docker image rm ubuntu:latest # 旧的命令格式如下： $ docker rmi ubuntu:latest