淺談Docker鏡像列表中的none:none是什么

更新時(shí)間：2023年11月23日 17:06:23 作者：程序員欣宸

這篇文章主要介紹了Docker鏡像列表中的none:none問(wèn)題,具有很好的參考價(jià)值,希望對(duì)大家有所幫助,如有錯(cuò)誤或未考慮完全的地方,望不吝賜教

官方解釋

來(lái)自官方的解釋如下圖紅框所示，地址是：https://docs.docker.com/config/pruning/

怎么來(lái)的

結(jié)合第一幅圖，梳理一下dangling images怎么產(chǎn)生的：第一次構(gòu)建鏡像時(shí)生成的鏡像ID為079dbd67f9f4，此鏡像會(huì)被構(gòu)建工具加上標(biāo)簽bolingcavalry/eureka-server:0.0.1-SNAPSHOT；

第二次構(gòu)建鏡像時(shí)生成的鏡像ID為e40a97f764ef，此鏡像會(huì)被構(gòu)建工具加上標(biāo)簽bolingcavalry/eureka-server:0.0.1-SNAPSHOT，

Docker會(huì)移除079dbd67f9f4的標(biāo)簽，此時(shí)079dbd67f9f4就變成了dangling images，在鏡像列表中展示為<none>:<none>

準(zhǔn)備實(shí)戰(zhàn)

接下來(lái)通過(guò)實(shí)際操作來(lái)復(fù)現(xiàn)此問(wèn)題，并做一些有趣的測(cè)試；

操作的主要內(nèi)容是將一個(gè)maven工程構(gòu)建成Docker鏡像，以下是環(huán)境信息：

操作系統(tǒng)：Ubuntu 18.04.2 LTS
Docker：18.06.1-ce
Java：1.8.0_191
Maven：3.6.0

實(shí)戰(zhàn)源碼下載

如果您不想寫代碼，也可以在Github下載整個(gè)maven工程，地址和鏈接信息如下表所示：

名稱	鏈接	備注
項(xiàng)目主頁(yè)	https://github.com/zq2599/blog_demos	該項(xiàng)目在GitHub上的主頁(yè)
git倉(cāng)庫(kù)地址(https)	https://github.com/zq2599/blog_demos.git	該項(xiàng)目源碼的倉(cāng)庫(kù)地址，https協(xié)議
git倉(cāng)庫(kù)地址(ssh)	git@github.com:zq2599/blog_demos.git	該項(xiàng)目源碼的倉(cāng)庫(kù)地址，ssh協(xié)議

這個(gè)git項(xiàng)目中有多個(gè)文件夾，本章源碼在springcloudscaledemo這個(gè)文件夾下，如下圖紅框所示：

springcloudscaledemo文件夾內(nèi)有三個(gè)工程，本次實(shí)戰(zhàn)用到的是eureka-server，如下圖：

實(shí)戰(zhàn)操作

接下來(lái)一起開發(fā)一個(gè)簡(jiǎn)單的java項(xiàng)目：

基于Maven創(chuàng)建一個(gè)springboot工程，pom.xml內(nèi)容如下，主要注意plugins節(jié)點(diǎn)中的插件，該插件是用來(lái)構(gòu)建鏡像的：

<?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鏡像相關(guān)的配置信息-->
				<configuration>
					<!--鏡像名，這里用工程名-->
					<imageName>bolingcavalry/${project.artifactId}</imageName>
					<!--TAG,這里用工程版本號(hào)-->
					<imageTags>
						<imageTag>${project.version}</imageTag>
					</imageTags>
					<!--鏡像的FROM，使用java官方鏡像-->
					<baseImage>java:8u111-jdk</baseImage>
					<!--該鏡像的容器啟動(dòng)后，直接運(yùn)行spring boot工程-->
					<entryPoint>["java", "-jar", "/${project.build.finalName}.jar"]</entryPoint>
					<!--構(gòu)建鏡像的配置信息-->
					<resources>
						<resource>
							<targetPath>/</targetPath>
							<directory>${project.build.directory}</directory>
							<include>${project.build.finalName}.jar</include>
						</resource>
					</resources>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

application.properties內(nèi)容如下，可見該應(yīng)用其實(shí)就是springcloud中的eureka身份：

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/

啟動(dòng)類是EurekaServerApplication，內(nèi)容如下：

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {

	public static void main(String[] args) {
		SpringApplication.run(EurekaServerApplication.class, args);
	}
}

現(xiàn)在工程已經(jīng)創(chuàng)建好了，可以開始構(gòu)建了；

構(gòu)建鏡像在pom.xml所在目錄執(zhí)行以下命令即可

構(gòu)建鏡像

mvn clean package -U -DskipTests docker:dockerBuild

構(gòu)建成功后，用docker images命令查看本地鏡像列表如下，新增了ID為90b736eb388e的鏡像：

[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

再次執(zhí)行命令mvn clean package -U -DskipTests docker:build，也就是再構(gòu)建一次；

構(gòu)建完成后查看鏡像列表，ID為90b736eb388e的鏡像已經(jīng)成為dangling images，標(biāo)簽bolingcavalry/eureka-server:0.0.1-SNAPSHOT已經(jīng)被新鏡像be262f101e2c占有：

[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

此時(shí)，如果您的鏡像列表出現(xiàn)<none>:<none>，您也能分析出此現(xiàn)象的來(lái)源了，接下來(lái)試試如何清理dangling images。

清理dangling images

如下所示，執(zhí)行命令docker image prune即可刪除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

再次查看，發(fā)現(xiàn)90b736eb388e已經(jīng)不在列表中：

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

一點(diǎn)疑問(wèn)

再來(lái)看看官方對(duì)dangling images的解釋，如下所示，有兩個(gè)條件：沒(méi)有標(biāo)簽、并且不再被容器使用：

我的疑問(wèn)：如果沒(méi)有標(biāo)簽，但是正在被容器使用的鏡像，應(yīng)該不算dangling images吧，此時(shí)如果執(zhí)行命令docker image prune會(huì)怎么樣呢？

我的猜測(cè)：docker image prune是用來(lái)清理dangling images的，如果鏡像正在被使用那就不算dangling images，那就不會(huì)被清理掉；

還是動(dòng)手來(lái)試試吧：

執(zhí)行以下命令會(huì)用鏡像bolingcavalry/eureka-server:0.0.1-SNAPSHOT創(chuàng)建一個(gè)容器：

docker run -idt bolingcavalry/eureka-server:0.0.1-SNAPSHOT

再次執(zhí)行命令mvn clean package -U -DskipTests docker:build，也就是再構(gòu)建一次；

查看鏡像信息如下，此時(shí)be262f101e2c在列表中已經(jīng)顯示成了<none>:<none>：

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

執(zhí)行命令docker ps查看容器，發(fā)現(xiàn)IMAGE字段已經(jīng)變成了ID(之前是bolingcavalry/eureka-server:0.0.1-SNAPSHOT)：

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

執(zhí)行命令docker image prune，再查看鏡像列表，如下，可見be262f101e2c依舊在列表中，沒(méi)有被清理掉，符合之前的猜測(cè)：被容器用到的鏡像不是dangling images，用命令docker image prune無(wú)法清除：

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