2.3.3.1. 前言
在前面已经详细介绍了 Dockerfile 文件指令与用法。本节就通过前文介绍的指令基于 centos 基础镜像构建 jvm8 环境。
2.3.3.2. 查找 Centos 基础镜像
在笔者是基于 centos 基础镜像构建 jvm8 环境。所以在构建镜像之前先在镜像库中查找 centos 镜像及版本信息。执行如下命令：
$ docker search centos
命令示例：
$ docker search centos
NAME DESCRIPTION STARS OFFICIAL AUTOMATED
centos The official build of CentOS. 5032 [OK]
ansible/centos7-ansible Ansible on Centos7 119 [OK]
jdeathe/centos-ssh CentOS-6 6.10 x86_64 / CentOS-7 7.5.1804 x86… 102 [OK]
consol/centos-xfce-vnc Centos container with "headless" VNC session… 73 [OK]
imagine10255/centos6-lnmp-php56 centos6-lnmp-php56 48 [OK]
centos/mysql-57-centos7 MySQL 5.7 SQL database server 43
tutum/centos Simple CentOS docker image with SSH access 43
gluster/gluster-centos Official GlusterFS Image [ CentOS-7 + Glust… 37 [OK]
openshift/base-centos7 A Centos7 derived base image for Source-To-I… 36
centos/postgresql-96-centos7 PostgreSQL is an advanced Object-Relational … 35
centos/python-35-centos7 Platform for building and running Python 3.5… 32
kinogmt/centos-ssh CentOS with SSH 25 [OK]
openshift/jenkins-2-centos7 A Centos7 based Jenkins v2.x image for use w… 18
centos/php-56-centos7 Platform for building and running PHP 5.6 ap… 17
pivotaldata/centos-gpdb-dev CentOS image for GPDB development. Tag names… 8
openshift/wildfly-101-centos7 A Centos7 based WildFly v10.1 image for use … 6
openshift/jenkins-1-centos7 DEPRECATED: A Centos7 based Jenkins v1.x ima… 4
darksheer/centos Base Centos Image -- Updated hourly 3 [OK]
pivotaldata/centos Base centos, freshened up a little with a Do… 2
pivotaldata/centos-mingw Using the mingw toolchain to cross-compile t… 2
pivotaldata/centos-gcc-toolchain CentOS with a toolchain, but unaffiliated wi… 1
blacklabelops/centos CentOS Base Image! Built and Updates Daily! 1 [OK]
pivotaldata/centos7-test CentosOS 7 image for GPDB testing 0
smartentry/centos centos with smartentry 0 [OK]
pivotaldata/centos7-build CentosOS 7 image for GPDB compilation 0
可以看到名称为 centos 的镜像是官方镜像，并别 star 高达 5k，就使用这个镜像作为基础镜像。
注意： 在 centos 镜像前没有组织名称，原因是默认为官方镜像 docker/centos。因此省略不显示。
2.3.3.3. 上传 JVM
现在进行创建一个 centos-jvm8 文件夹：
$ mkdir centos-jvm8
$ cd centos-jvm8/
$ ls
并将在 Oracle 官网 下载的 linux 版本 jvm8 上传至该文件夹：
$ rz
$ ls
jdk-8u181-linux-x64.tar.gz
注意：该文件不需要进行解压，还记得在 Dockerfile 详解 章节结束的 ADD 指令吗？该指令会自动解压 tar 文件为目录！
2.3.3.4. 编写 Dockerfile
在该文件夹下继续创建文件 Dockerfile：
$ touch Dockerfile
$ ls
Dockerfile jdk-8u181-linux-x64.tar.gz
创建完成之后进行 vim 编辑，内容如下所示：
#This Dockerfile use centos image
# Version 1 - EDITION 1
# Author: MinGRn
# Base Image
FROM centos
# Maintainer: MinGRn <[email protected]>
MAINTAINER MinGRn [email protected]
# Add JVM To Base Image
ADD jdk-8u181-linux-x64.tar.gz /opt/jvm
# JVM Environment
ENV JAVA_HOME /opt/jvm/jdk1.8.0_181
ENV CLASSPATH $JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
ENV PATH $PATH:$JAVA_HOME/bin
ENTRYPOINT ["java", "-version"]
FROM 指令后直接跟 centos 并没有写版本后会默认选择 centos lastest 版本作为基础镜像。
ADD jdk-8u181-linux-x64.tar.gz /opt/jvm 指令是将 jdk-8u181-linux-x64.tar.gz 文件添加进入基础镜像的 /opt/jvm 目录，如果没有该目录会进行创建。其中压缩包是 Dockerfile 的相对路径。一般在创建时为了防止路径出错都会将目标文件放置 Dockerfile 的同一目录。
ENV JAVA_HOME /opt/jvm/jdk1.8.0_181
ENV CLASSPATH $JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
ENV PATH $PATH:$JAVA_HOME/bin
这三个指令时配置基于基础镜像配置 JVM 环境变量。
ENV JAVA_HOME /opt/jvm/jdk1.8.0_181 这里直接写 jdk1.8.0_181 的原因是 jdk-8u181-linux-x64.tar.gz 压缩包解压后的目录就是该目录。不信？你可以试试。
ENTRYPOINT ["java", "-version"] 指令是创建容器后的启动命令打印 jvm 版本信息。当然，也可以直接使用 CMD 指令，关于 CMD 与 Entrypoint 指令的区别见： RUN & CMD & Entrypoint
现在就可以执行指令进行构建镜像了。
2.3.3.5. 构建镜像
构建镜像指令是 docker build 具体如下：
$ docker build --help
Usage: docker build [OPTIONS] PATH | URL | -
Build an image from a Dockerfile
Options:
--add-host list Add a custom host-to-IP mapping (host:ip)
--build-arg list Set build-time variables
--cache-from strings Images to consider as cache sources
--cgroup-parent string Optional parent cgroup for the container
--compress Compress the build context using gzip
--cpu-period int Limit the CPU CFS (Completely Fair Scheduler) period
--cpu-quota int Limit the CPU CFS (Completely Fair Scheduler) quota
-c, --cpu-shares int CPU shares (relative weight)
--cpuset-cpus string CPUs in which to allow execution (0-3, 0,1)
--cpuset-mems string MEMs in which to allow execution (0-3, 0,1)
--disable-content-trust Skip image verification (default true)
-f, --file string Name of the Dockerfile (Default is 'PATH/Dockerfile')
--force-rm Always remove intermediate containers
--iidfile string Write the image ID to the file
--isolation string Container isolation technology
--label list Set metadata for an image
-m, --memory bytes Memory limit
--memory-swap bytes Swap limit equal to memory plus swap: '-1' to enable unlimited swap
--network string Set the networking mode for the RUN instructions during build (default "default")
--no-cache Do not use cache when building the image
--pull Always attempt to pull a newer version of the image
-q, --quiet Suppress the build output and print image ID on success
--rm Remove intermediate containers after a successful build (default true)
--security-opt strings Security options
--shm-size bytes Size of /dev/shm
-t, --tag list Name and optionally a tag in the 'name:tag' format
--target string Set the target build stage to build.
--ulimit ulimit Ulimit options (default [])
其中 -t 选项是将镜像打标签。在构建镜像时一定要增加该标签，不然会默认该版本镜像为 lastest。
现在在当前目录执行构建标签指令：
$ docker build -t jvm8:v1.0.0 .
命令执行示例：
$ docker build -t jvm8:v1.0.0 .
Sending build context to Docker daemon 185.7MB
Step 1/7 : FROM centos
---> 1e1148e4cc2c
Step 2/7 : MAINTAINER MinGRn [email protected]
---> Running in 4be5b85528a7
Removing intermediate container 4be5b85528a7
---> ad64fb563756
Step 3/7 : ADD jdk-8u181-linux-x64.tar.gz /opt/jvm
---> d939416fd6a0
Step 4/7 : ENV JAVA_HOME /opt/jvm/jdk1.8.0_181
---> Running in 11d8ce8b6914
Removing intermediate container 11d8ce8b6914
---> e736522a5ccd
Step 5/7 : ENV CLASSPATH $JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
---> Running in 351929607b74
Removing intermediate container 351929607b74
---> 192b28b23407
Step 6/7 : ENV PATH $PATH:$JAVA_HOME/bin
---> Running in 28875d5a1ae7
Removing intermediate container 28875d5a1ae7
---> 30786547f925
Step 7/7 : ENTRYPOINT ["java", "-version"]
---> Running in 87c0fe35c366
Removing intermediate container 87c0fe35c366
---> 9ef7f38f2bf1
Successfully built 9ef7f38f2bf1
Successfully tagged jvm8:v1.0.0
可以看到已经提示构建成功，并且 tag 是 v1.0.0。现在执行命令查看是否存在该镜像：
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
jvm8 v1.0.0 9ef7f38f2bf1 29 seconds ago 583MB
ifkeeper/centos-jvm8 v1.0.0 e15334134272 18 hours ago 583MB
centos latest 1e1148e4cc2c 3 days ago 202MB
openjdk latest 8e7eacedab93 4 days ago 986MB
可以看到大小为 583M。
现在将该运行该经常成为一个容器，看是否打印 JVM Version 信息：
$ docker run 9ef7f38f2bf1
or
$ docker run jvm8:v1.0.0
命令执行示例：
$ docker run 9ef7f38f2bf1
java version "1.8.0_181"
Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)
成功打印 JVM Version 信息，说明镜像构建没有问题！
现在来看下如何将镜像上传至镜像仓库。
2.3.3.6. 上传镜像至仓库
打开 Docker Hub 然后登录自己的账号。
然后创建仓库，仓库名为 jvm8：
这里仓库的组织为 ifkeeper。现在回到命令，将构建的 jvm8 镜像进行打标签，打标签命令：
$ docker tag --help
Usage: docker tag SOURCE_IMAGE[:TAG] TARGET_IMAGE[:TAG]
Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
命令示例：
$ docker tag jvm8:v1.0.0 ifkeeper/jvm8:v1.0.0
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ifkeeper/jvm8 v1.0.0 9ef7f38f2bf1 18 minutes ago 583MB
jvm8 v1.0.0 9ef7f38f2bf1 18 minutes ago 583MB
可以看到，jvm8 成功被打成标签。
注意： 在打标签时要将组织名称加上。比如：笔者想将该镜像推送至 ifkeeper 组织，镜像名称为 jvm8，版本号为 v1.0.0。所以笔者的目标标签为 ifkeeper/jvm8:v1.0.0。
现在，进行登录 Docker Hub，登录命令如下：
$ docker login --help
Usage: docker login [OPTIONS] [SERVER]
Log in to a Docker registry
Options:
-p, --password string Password
--password-stdin Take the password from stdin
-u, --username string Username
笔者由于之前已经登陆过，这里直接输入命令 docker login 即可登录，如下：
$ docker login
Authenticating with existing credentials...
WARNING! Your password will be stored unencrypted in /root/.docker/config.json.
Configure a credential helper to remove this warning. See
https://docs.docker.com/engine/reference/commandline/login/#credentials-store
Login Succeeded
现在登录成功，就将镜像推送至仓库。推送命令：
$ docker push --help
Usage: docker push [OPTIONS] NAME[:TAG]
Push an image or a repository to a registry
Options:
--disable-content-trust Skip image signing (default true)
命令执行示例：
$ docker push ifkeeper/jvm8:v1.0.0
The push refers to repository [docker.io/ifkeeper/jvm8]
2c218a57b7e7: Pushed
071d8bd76517: Mounted from ifkeeper/centos-jvm8
v1.0.0: digest: sha256:dc3c695f49433ddbc8b821bd5b0019b370ff56d338f8885c6b336780fcb491bb size: 742
现在登录 Docker Hub 看是否成功推送：
镜像以成功推送至仓库！
2.3.3.7. 查看镜像信息
现在可以通过 docker inspect 命令查看镜像构建信息，该命令信息如下：
$ 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
命令执行示例：
$ docker inspect 9ef7f38f2bf1
[
{
"Id": "sha256:9ef7f38f2bf11b5741b92eb48f3fa8f6a1bdc1a4a4d7102e2e601f6f2f440461",
"RepoTags": [
"ifkeeper/jvm8:v1.0.0",
"jvm8:v1.0.0"
],
"RepoDigests": [
"ifkeeper/jvm8@sha256:dc3c695f49433ddbc8b821bd5b0019b370ff56d338f8885c6b336780fcb491bb"
],
"Parent": "sha256:30786547f925fa91c37bd5980dcb0c184641dd96626fed60a641f93e253630b4",
"Comment": "",
"Created": "2018-12-09T07:25:22.002921457Z",
"Container": "87c0fe35c36672bace745ce01e3e7588913bcbbfab3708c8817dc8123f191815",
"ContainerConfig": {
"Hostname": "87c0fe35c366",
"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:/opt/jvm/jdk1.8.0_181/bin",
"JAVA_HOME=/opt/jvm/jdk1.8.0_181",
"CLASSPATH=/opt/jvm/jdk1.8.0_181/lib/dt.jar:/opt/jvm/jdk1.8.0_181/lib/tools.jar"
],
"Cmd": [
"/bin/sh",
"-c",
"#(nop) ",
"ENTRYPOINT [\"java\" \"-version\"]"
],
"ArgsEscaped": true,
"Image": "sha256:30786547f925fa91c37bd5980dcb0c184641dd96626fed60a641f93e253630b4",
"Volumes": null,
"WorkingDir": "",
"Entrypoint": [
"java",
"-version"
],
"OnBuild": null,
"Labels": {
"org.label-schema.build-date": "20181205",
"org.label-schema.license": "GPLv2",
"org.label-schema.name": "CentOS Base Image",
"org.label-schema.schema-version": "1.0",
"org.label-schema.vendor": "CentOS"
}
},
"DockerVersion": "18.09.0",
"Author": "MinGRn [email protected]",
"Config": {
"Hostname": "",
"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:/opt/jvm/jdk1.8.0_181/bin",
"JAVA_HOME=/opt/jvm/jdk1.8.0_181",
"CLASSPATH=/opt/jvm/jdk1.8.0_181/lib/dt.jar:/opt/jvm/jdk1.8.0_181/lib/tools.jar"
],
"Cmd": null,
"ArgsEscaped": true,
"Image": "sha256:30786547f925fa91c37bd5980dcb0c184641dd96626fed60a641f93e253630b4",
"Volumes": null,
"WorkingDir": "",
"Entrypoint": [
"java",
"-version"
],
"OnBuild": null,
"Labels": {
"org.label-schema.build-date": "20181205",
"org.label-schema.license": "GPLv2",
"org.label-schema.name": "CentOS Base Image",
"org.label-schema.schema-version": "1.0",
"org.label-schema.vendor": "CentOS"
}
},
"Architecture": "amd64",
"Os": "linux",
"Size": 583469631,
"VirtualSize": 583469631,
"GraphDriver": {
"Data": {
"LowerDir": "/var/lib/docker/overlay2/f0a77ed5662eaa4757e8765055cebdc5fb33f297ed9b5cecb46efaa494e5ca75/diff",
"MergedDir": "/var/lib/docker/overlay2/a3a109cea18169342f1d6281881fc149b78511216d418b6fa5e507dfbcb54e30/merged",
"UpperDir": "/var/lib/docker/overlay2/a3a109cea18169342f1d6281881fc149b78511216d418b6fa5e507dfbcb54e30/diff",
"WorkDir": "/var/lib/docker/overlay2/a3a109cea18169342f1d6281881fc149b78511216d418b6fa5e507dfbcb54e30/work"
},
"Name": "overlay2"
},
"RootFS": {
"Type": "layers",
"Layers": [
"sha256:071d8bd765171080d01682844524be57ac9883e53079b6ac66707e192ea25956",
"sha256:2c218a57b7e7b5504cbfb63802743e718c43f7a34f46ef91d8b95b7ffb69dd46"
]
},
"Metadata": {
"LastTagTime": "2018-12-09T15:43:21.810359161+08:00"
}
}
]
在镜像信息中可以看到 镜像id、镜像仓库与标签、镜像作者、镜像命令信息。这些信息很重要，比如追溯源镜像信息。具体后面作讲解。