SpringBoot Image building fails when DOCKER_HOST is set to a local socket prefixed with unix://

On our build server we have an environment varialbe DOCKER_HOST="unix:///var/run/docker.sock" set. This has not been a problem with the docker client nor with the io.fabric8: docker-maven-plugin.

spring-boot:build-image fails, though.

This can be reproduced locally like so:

export DOCKER_HOST="unix:///var/run/docker.sock"
mvn spring-boot:build-image -DskipTests -X
...
[ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.3.1.RELEASE:build-image (default-cli) on project test: Execution default-cli of goal org.springframework.boot:spring-boot-maven-plugin:2.3.1.RELEASE:build-image failed: Connection to the Docker daemon at '/var/run/docker.sock' failed with error "/var/run/docker.sock: Name or service not known"; ensure the Docker daemon is running and accessible: Unknown host /var/run/docker.sock: Name or service not known -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.3.1.RELEASE:build-image (default-cli) on project test: Execution default-cli of goal org.springframework.boot:spring-boot-maven-plugin:2.3.1.RELEASE:build-image failed: Connection to the Docker daemon at '/var/run/docker.sock' failed with error "/var/run/docker.sock: Name or service not known"; ensure the Docker daemon is running and accessible
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:215)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:956)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.apache.maven.wrapper.BootstrapMainStarter.start (BootstrapMainStarter.java:39)
    at org.apache.maven.wrapper.WrapperExecutor.execute (WrapperExecutor.java:122)
    at org.apache.maven.wrapper.MavenWrapperMain.main (MavenWrapperMain.java:55)
Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default-cli of goal org.springframework.boot:spring-boot-maven-plugin:2.3.1.RELEASE:build-image failed: Connection to the Docker daemon at '/var/run/docker.sock' failed with error "/var/run/docker.sock: Name or service not known"; ensure the Docker daemon is running and accessible
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:148)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:956)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.apache.maven.wrapper.BootstrapMainStarter.start (BootstrapMainStarter.java:39)
    at org.apache.maven.wrapper.WrapperExecutor.execute (WrapperExecutor.java:122)
    at org.apache.maven.wrapper.MavenWrapperMain.main (MavenWrapperMain.java:55)
Caused by: org.springframework.boot.buildpack.platform.docker.transport.DockerConnectionException: Connection to the Docker daemon at '/var/run/docker.sock' failed with error "/var/run/docker.sock: Name or service not known"; ensure the Docker daemon is running and accessible
    at org.springframework.boot.buildpack.platform.docker.transport.HttpClientTransport.execute (HttpClientTransport.java:141)
    at org.springframework.boot.buildpack.platform.docker.transport.HttpClientTransport.post (HttpClientTransport.java:82)
    at org.springframework.boot.buildpack.platform.docker.DockerApi$ImageApi.pull (DockerApi.java:155)
    at org.springframework.boot.buildpack.platform.build.Builder.pullBuilder (Builder.java:85)
    at org.springframework.boot.buildpack.platform.build.Builder.build (Builder.java:63)
    at org.springframework.boot.maven.BuildImageMojo.buildImage (BuildImageMojo.java:136)
    at org.springframework.boot.maven.BuildImageMojo.execute (BuildImageMojo.java:128)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:956)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.apache.maven.wrapper.BootstrapMainStarter.start (BootstrapMainStarter.java:39)
    at org.apache.maven.wrapper.WrapperExecutor.execute (WrapperExecutor.java:122)
    at org.apache.maven.wrapper.MavenWrapperMain.main (MavenWrapperMain.java:55)
Caused by: java.net.UnknownHostException: /var/run/docker.sock: Name or service not known
    at java.net.Inet6AddressImpl.lookupAllHostAddr (Native Method)
    at java.net.InetAddress$PlatformNameService.lookupAllHostAddr (InetAddress.java:929)
    at java.net.InetAddress.getAddressesFromNameService (InetAddress.java:1515)
    at java.net.InetAddress$NameServiceAddresses.get (InetAddress.java:848)
    at java.net.InetAddress.getAllByName0 (InetAddress.java:1505)
    at java.net.InetAddress.getAllByName (InetAddress.java:1364)
    at java.net.InetAddress.getAllByName (InetAddress.java:1298)
    at org.apache.http.impl.conn.SystemDefaultDnsResolver.resolve (SystemDefaultDnsResolver.java:45)
    at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect (DefaultHttpClientConnectionOperator.java:112)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect (PoolingHttpClientConnectionManager.java:376)
    at org.apache.http.impl.execchain.MainClientExec.establishRoute (MainClientExec.java:393)
    at org.apache.http.impl.execchain.MainClientExec.execute (MainClientExec.java:236)
    at org.apache.http.impl.execchain.ProtocolExec.execute (ProtocolExec.java:186)
    at org.apache.http.impl.execchain.RetryExec.execute (RetryExec.java:89)
    at org.apache.http.impl.execchain.RedirectExec.execute (RedirectExec.java:110)
    at org.apache.http.impl.client.InternalHttpClient.doExecute (InternalHttpClient.java:185)
    at org.apache.http.impl.client.CloseableHttpClient.execute (CloseableHttpClient.java:118)
    at org.springframework.boot.buildpack.platform.docker.transport.HttpClientTransport.execute (HttpClientTransport.java:128)
    at org.springframework.boot.buildpack.platform.docker.transport.HttpClientTransport.post (HttpClientTransport.java:82)
    at org.springframework.boot.buildpack.platform.docker.DockerApi$ImageApi.pull (DockerApi.java:155)
    at org.springframework.boot.buildpack.platform.build.Builder.pullBuilder (Builder.java:85)
    at org.springframework.boot.buildpack.platform.build.Builder.build (Builder.java:63)
    at org.springframework.boot.maven.BuildImageMojo.buildImage (BuildImageMojo.java:136)
    at org.springframework.boot.maven.BuildImageMojo.execute (BuildImageMojo.java:128)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:956)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.apache.maven.wrapper.BootstrapMainStarter.start (BootstrapMainStarter.java:39)
    at org.apache.maven.wrapper.WrapperExecutor.execute (WrapperExecutor.java:122)
    at org.apache.maven.wrapper.MavenWrapperMain.main (MavenWrapperMain.java:55)
[ERROR] 
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException

Error does not occurr when

unset DOCKER_HOST
mvn spring-boot:build-image -DskipTests
...
[INFO] BUILD SUCCESS

Comment From: wilkinsona

Thanks for the report. It looks like we're not handling the unix scheme correctly. Could you please try with DOCKER_HOST=/var/run/docker.sock?

Comment From: schnatterer

@wilkinsona thanks for your response. The following succeeds:

export DOCKER_HOST='/var/run/docker.sock'
mvn spring-boot:build-image -DskipTests  

Comment From: wilkinsona

@schnatterer Thank you for trying that. We're seeing the same behaviour.

Comment From: schnatterer

Thanks for the immediate fix, @wilkinsona

Comment From: jamesward

Note that in Gradle I got this error:

Docker API call to '/var/run/docker.sock/v1.24/images/create?fromImage=gcr.io%2Fpaketo-buildpacks%2Fb
uilder%3Abase-platform-api-0.3' failed with status code 500 "/var/run/docker.sock: Name or service not 
known"

Putting this here for others searching for the error.