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在构建过Docker镜像的电脑上查看本地镜像列表,有可能看到下图红框中的镜像,在列表中展示为<none>:<none>:
这种镜像在Docker官方文档中被称作dangling images,指的是没有标签并且没有被容器使用的镜像。
来自官方的解释如下图红框所示,地址是:https://docs.docker.com/config/pruning/
结合第一幅图,梳理一下dangling images怎么产生的:
接下来通过实际操作来复现此问题,并做一些有趣的测试;
操作的主要内容是将一个maven工程构建成Docker镜像,以下是环境信息:
如果您不想写代码,也可以在Github下载整个maven工程,地址和链接信息如下表所示:
名称 | 链接 | 备注 |
---|---|---|
项目主页 | https://github.com/zq2599/blog_demos | 该项目在GitHub上的主页 |
git仓库地址(https) | https://github.com/zq2599/blog_demos.git | 该项目源码的仓库地址,https协议 |
git仓库地址(ssh) | git@github.com:zq2599/blog_demos.git | 该项目源码的仓库地址,ssh协议 |
这个git项目中有多个文件夹,本章源码在springcloudscaledemo这个文件夹下,如下图红框所示:
springcloudscaledemo文件夹内有三个工程,本次实战用到的是eureka-server,如下图:
接下来一起开发一个简单的java项目:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.bolingcavalry</groupId>
<artifactId>eureka-server</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>eureka-server</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.9.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<spring-cloud.version>Edgware.SR1</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka-server</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<!--新增的docker maven插件-->
<plugin>
<groupId>com.spotify</groupId>
<artifactId>docker-maven-plugin</artifactId>
<version>0.4.12</version>
<!--docker镜像相关的配置信息-->
<configuration>
<!--镜像名,这里用工程名-->
<imageName>bolingcavalry/${project.artifactId}</imageName>
<!--TAG,这里用工程版本号-->
<imageTags>
<imageTag>${project.version}</imageTag>
</imageTags>
<!--镜像的FROM,使用java官方镜像-->
<baseImage>java:8u111-jdk</baseImage>
<!--该镜像的容器启动后,直接运行spring boot工程-->
<entryPoint>["java", "-jar", "/${project.build.finalName}.jar"]</entryPoint>
<!--构建镜像的配置信息-->
<resources>
<resource>
<targetPath>/</targetPath>
<directory>${project.build.directory}</directory>
<include>${project.build.finalName}.jar</include>
</resource>
</resources>
</configuration>
</plugin>
</plugins>
</build>
</project>
server.port=8080
eureka.instance.hostname=localhost
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
eureka.client.serviceUrl.defaultZone=http://${eureka.instance.hostname}:${server.port}/eureka/
@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {
public static void main(String[] args) {
SpringApplication.run(EurekaServerApplication.class, args);
}
}
现在工程已经创建好了,可以开始构建了;
mvn clean package -U -DskipTests docker:build
[INFO] Built bolingcavalry/eureka-server
[INFO] Tagging bolingcavalry/eureka-server with 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 10.918 s
[INFO] Finished at: 2019-06-01T08:36:59Z
[INFO] ------------------------------------------------------------------------
root@hedy:/home/willzhao/temp/201906/01/eureka-server# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
bolingcavalry/eureka-server 0.0.1-SNAPSHOT 90b736eb388e 5 seconds ago 683MB
bolingcavalry/eureka-server latest 90b736eb388e 5 seconds ago 683MB
java 8u111-jdk d23bdf5b1b1b 2 years ago 643MB
[INFO] Built bolingcavalry/eureka-server
[INFO] Tagging bolingcavalry/eureka-server with 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 10.985 s
[INFO] Finished at: 2019-06-01T08:44:49Z
[INFO] ------------------------------------------------------------------------
root@hedy:/home/willzhao/temp/201906/01/eureka-server# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
bolingcavalry/eureka-server 0.0.1-SNAPSHOT be262f101e2c About a minute ago 683MB
bolingcavalry/eureka-server latest be262f101e2c About a minute ago 683MB
<none> <none> 90b736eb388e 9 minutes ago 683MB
java 8u111-jdk d23bdf5b1b1b 2 years ago 643MB
此时,如果您的镜像列表出现<none>:<none>,您也能分析出此现象的来源了,接下来试试如何清理dangling images。
root@hedy:/home/willzhao/temp/201906/01/eureka-server# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
bolingcavalry/eureka-server 0.0.1-SNAPSHOT be262f101e2c About a minute ago 683MB
bolingcavalry/eureka-server latest be262f101e2c About a minute ago 683MB
<none> <none> 90b736eb388e 9 minutes ago 683MB
java 8u111-jdk d23bdf5b1b1b 2 years ago 643MB
root@hedy:/home/willzhao/temp/201906/01/eureka-server# docker image prune
WARNING! This will remove all dangling images.
Are you sure you want to continue? [y/N] y
Deleted Images:
deleted: sha256:90b736eb388e42df2e4bc2ab3c8770a9a5f7563bb5af2493b88428c610f14f6b
deleted: sha256:db3657b5e27b7bf6c780e3280d6f2e24ffc26592a14b4efa651000130294b429
deleted: sha256:afd10ec003e3132ea5e1c489ba5e51f53b0759351bdc175184ba82daaac178d1
Total reclaimed space: 39.94MB
root@hedy:/home/willzhao/temp/201906/01/eureka-server# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
bolingcavalry/eureka-server 0.0.1-SNAPSHOT be262f101e2c 39 minutes ago 683MB
bolingcavalry/eureka-server latest be262f101e2c 39 minutes ago 683MB
java 8u111-jdk d23bdf5b1b1b 2 years ago 643MB
再来看看官方对dangling images的解释,如下所示,有两个条件:没有标签、并且不再被容器使用:
我的疑问:如果没有标签,但是正在被容器使用的镜像,应该不算dangling images吧,此时如果执行命令docker image prune会怎么样呢?
我的猜测:docker image prune是用来清理dangling images的,如果镜像正在被使用那就不算dangling images,那就不会被清理掉;
还是动手来试试吧:
docker run -idt bolingcavalry/eureka-server:0.0.1-SNAPSHOT
root@hedy:/home/willzhao/temp/201906/01/eureka-server# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
bolingcavalry/eureka-server 0.0.1-SNAPSHOT f83762738051 4 seconds ago 683MB
bolingcavalry/eureka-server latest f83762738051 4 seconds ago 683MB
<none> <none> be262f101e2c About an hour ago 683MB
java 8u111-jdk d23bdf5b1b1b 2 years ago 643MB
root@hedy:/home/willzhao/temp/201906/01/eureka-server# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
f4e9b7aa6d25 be262f101e2c "java -jar /eureka-s…" 7 minutes ago Up 7 minutes gallant_bell
root@hedy:/home/willzhao/temp/201906/01/eureka-server# docker image prune
WARNING! This will remove all dangling images.
Are you sure you want to continue? [y/N] y
Total reclaimed space: 0B
root@hedy:/home/willzhao/temp/201906/01/eureka-server# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
bolingcavalry/eureka-server 0.0.1-SNAPSHOT f83762738051 5 minutes ago 683MB
bolingcavalry/eureka-server latest f83762738051 5 minutes ago 683MB
<none> <none> be262f101e2c About an hour ago 683MB
java 8u111-jdk d23bdf5b1b1b 2 years ago 643MB
至此,对Docker镜像列表中的none:none已经了解,希望在您有类似疑惑时本文可以提供一些参考。