I found the same issue:

When runs on local:
2019-06-13 09:02:54.437 INFO --- [ main] [] org.testcontainers.DockerClientFactory : Docker host IP address is localhost
2019-06-13 09:02:55.222 INFO --- [ main] [] org.testcontainers.DockerClientFactory : Connected to docker:
Server Version: 18.09.0
API Version: 1.39
Operating System: Docker for Windows
Total Memory: 1980 MB
2019-06-13 09:02:56.304 INFO --- [ main] [] o.t.utility.RegistryAuthLocator : Credentials not found for host (quay.io) when using credential helper/store (docker-credential-wincred)
2019-06-13 09:03:02.008 INFO --- [ main] [] org.testcontainers.DockerClientFactory : Ryuk started - will monitor and terminate Testcontainers containers on JVM exit
?? Checking the system...
? Docker version should be at least 1.6.0
2019-06-13 09:03:02.373 INFO --- [ main] [] docker[google/cloud-sdk:latest] : Creating container for image: google/cloud-sdk:latest
2019-06-13 09:03:03.279 INFO --- [ main] [] o.t.utility.RegistryAuthLocator : Credentials not found for host (index.docker.io) when using credential helper/store (docker-credential-wincred)
2019-06-13 09:03:03.924 INFO --- [ main] [] docker[google/cloud-sdk:latest] : Starting container with ID: e6e8bec7a9a026aa32245206bc80d21b985b7e35535a1fbae10aa9ad7f500164
2019-06-13 09:03:06.433 INFO --- [ main] [] docker[google/cloud-sdk:latest] : Container google/cloud-sdk:latest is starting: e6e8bec7a9a026aa32245206bc80d21b985b7e35535a1fbae10aa9ad7f500164
2019-06-13 09:03:11.020 INFO --- [ main] [] docker[google/cloud-sdk:latest] : Container google/cloud-sdk:latest started

When runs on Docker:
2019-06-13 09:19:01.624 INFO --- [ main] [] org.testcontainers.DockerClientFactory : Docker host IP address is XXX.XX.0.1
2019-06-13 09:19:01.716 INFO --- [ main] [] org.testcontainers.DockerClientFactory : Connected to docker:
Server Version: 18.09.2
API Version: 1.39
Operating System: Ubuntu 16.04.6 LTS
Total Memory: 5967 MB
2019-06-13 09:19:01.886 WARN --- [ main] [] o.t.utility.RegistryAuthLocator : Failure when attempting to lookup auth config (dockerImageName: quay.io/testcontainers/ryuk:0.2.2, configFile: /root/.docker/config.json. Falling back to docker-java default behaviour. Exception message: /root/.docker/config.json (No such file or directory)
2019-06-13 09:19:02.602 INFO --- [ main] [] org.testcontainers.DockerClientFactory : Ryuk started - will monitor and terminate Testcontainers containers on JVM exit
ℹ︎ Checking the system...
✔ Docker version should be at least 1.6.0
2019-06-13 09:19:02.822 INFO --- [ main] [] 🐳 [google/cloud-sdk:latest] : Creating container for image: google/cloud-sdk:latest
2019-06-13 09:19:02.822 WARN --- [ main] [] o.t.utility.RegistryAuthLocator : Failure when attempting to lookup auth config (dockerImageName: google/cloud-sdk:latest, configFile: /root/.docker/config.json. Falling back to docker-java default behaviour. Exception message: /root/.docker/config.json (No such file or directory)
2019-06-13 09:19:02.901 INFO --- [ main] [] 🐳 [google/cloud-sdk:latest] : Starting container with ID: bf2b3ee32a3599f04ec7676a8ed58a54b411a8b58e8859a5d56a1275860b267f
2019-06-13 09:19:03.433 INFO --- [ main] [] 🐳 [google/cloud-sdk:latest] : Container google/cloud-sdk:latest is starting: bf2b3ee32a3599f04ec7676a8ed58a54b411a8b58e8859a5d56a1275860b267f
2019-06-13 09:19:06.384 INFO --- [ main] [] 🐳 [google/cloud-sdk:latest] : Container google/cloud-sdk:latest started

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you believe this is a mistake, please reply to this comment to keep it open. If there isn't one already, a PR to fix or at least reproduce the problem in a test case will always help us get back on track to tackle this.

I'm getting the same error when running Testcontainer in a GitLab CI/CD environment (docker in docker):

org.testcontainers.DockerClientFactory   : Ryuk started - will monitor and terminate Testcontainers containers on JVM exit
        ?? Checking the system...
        ? Docker version should be at least 1.6.0
        ? Docker environment should have more than 2GB free disk space
o.t.containers.SeleniumUtils             : Selenium API version 3.141.59 detected on classpath
d.141.59]                                : Creating container for image: selenium/standalone-chrome-debug:3.141.59
o.t.utility.RegistryAuthLocator          : Failure when attempting to lookup auth config (dockerImageName: selenium/standalone-chrome-debug:3.141.59, configFile: /root/.docker/config.json. Falling back to docker-java default behaviour. Exception message: /root/.docker/config.json (No such file or directory)
d.141.59]                                : Starting container with ID: e0650280f1262955a2cce15fb93e7edbc17bd217c68bb95785adc43b566d6a5d
d.141.59]                                : Container selenium/standalone-chrome-debug:3.141.59 is starting: e0650280f1262955a2cce15fb93e7edbc17bd217c68bb95785adc43b566d6a5d
d.141.59]                                : Container selenium/standalone-chrome-debug:3.141.59 started
o.o.selenium.remote.ProtocolHandshake    : Detected dialect: OSS
d.io/testcontainers/vnc-recorder:1.1.0]  : Creating container for image: quay.io/testcontainers/vnc-recorder:1.1.0
o.t.utility.RegistryAuthLocator          : Failure when attempting to lookup auth config (dockerImageName: quay.io/testcontainers/vnc-recorder:1.1.0, configFile: /root/.docker/config.json. Falling back to docker-java default behaviour. Exception message: /root/.docker/config.json (No such file or directory)

And then tests fail. Is there anything I can do?

That particular message is not a problem - it's simply saying that you don't have any credentials set for quay.io, which is correct. That warning is only expected to be helpful if you have docker images in an authenticated registry and there's an authentication problem.

Please disregard that and look at other possible causes if you have test failures!

I think we'd welcome a PR to clarify the wording for this log statement!

I also am having this problem when using Bitbucket piplines,

this is from the logs :

019-10-09 22:13:40,251 INFO o.t.d.DockerClientProviderStrategy [main] Will use 'okhttp' transport
2019-10-09 22:13:40,759 INFO o.t.d.EnvironmentAndSystemPropertyClientProviderStrategy [main] Found docker client settings from environment
2019-10-09 22:13:40,783 INFO o.t.d.DockerClientProviderStrategy [main] Found Docker environment with Environment variables, system properties and defaults. Resolved:
dockerHost=tcp://localhost:2375
apiVersion='{UNKNOWN_VERSION}'
registryUrl='https://index.docker.io/v1/'
registryUsername='root'
registryPassword='null'
registryEmail='null'
dockerConfig='DefaultDockerClientConfig[dockerHost=tcp://localhost:2375,registryUsername=root,registryPassword=,registryEmail=,registryUrl=https://index.docker.io/v1/,dockerConfigPath=/root/.docker,sslConfig=,apiVersion={UNKNOWN_VERSION},dockerConfig=]'

2019-10-09 22:13:40,786 INFO o.t.DockerClientFactory [main] Docker host IP address is localhost
2019-10-09 22:13:40,956 INFO o.t.DockerClientFactory [main] Connected to docker:
Server Version: 18.09.1
API Version: 1.39
Operating System: Alpine Linux v3.8 (containerized)
Total Memory: 31368 MB
2019-10-09 22:13:40,989 WARN o.t.u.RegistryAuthLocator [main] Failure when attempting to lookup auth config (dockerImageName: quay.io/testcontainers/ryuk:0.2.2, configFile: /root/.docker/config.json. Falling back to docker-java default behaviour. Exception message: /root/.docker/config.json (No such file or directory)
2019-10-09 22:13:41,879 WARN o.t.u.RegistryAuthLocator [main] Failure when attempting to lookup auth config (dockerImageName: quay.io/testcontainers/ryuk:0.2.2, configFile: /root/.docker/config.json. Falling back to docker-java default behaviour. Exception message: /root/.docker/config.json (No such file or directory)
2019-10-09 22:13:42,515 WARN o.t.u.ResourceReaper [testcontainers-ryuk] Can not connect to Ryuk at localhost:32768 java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at java.net.Socket.connect(Socket.java:538)
at java.net.Socket.(Socket.java:434)
at java.net.Socket.(Socket.java:211)
at org.testcontainers.utility.ResourceReaper.lambda$start$1(ResourceReaper.java:112)
at java.lang.Thread.run(Thread.java:748)

Figured out my problem.. upgrade. see also ticket #700

Hi @rnorth ! Agreed, the warning is "harmless", meaning, nothing is actually wrong.

This does, however, create extra build output which devs need to read and think about.

Is there a way to suppress it? A property setting or something ... ?

I'm scanning GitHub, and to look at the source of the warning (

Seems that maybe 'warn' is too important a level for this message in most circumstances. I have several of these warnings pertaining to Ryuk which I'm not expecting I'm using.

I think we could consider changing it. Perhaps to INFO level, plus make the message clearer that this is probably not a problem.

WDYT?