Supported tags and respective
Where to file issues:
the Docker Community
Supported Docker versions:
the latest release (down to 1.6 on a best-effort basis)
What is OpenJDK?
OpenJDK (Open Java Development Kit) is a free and open source implementation of the Java Platform, Standard Edition (Java SE). OpenJDK is the official reference implementation of Java SE since version 7.
Java is a registered trademark of Oracle and/or its affiliates.
How to use this image
Start a Java instance in your app
The most straightforward way to use this image is to use a Java container as both the build and runtime environment. In your
Dockerfile, writing something along the lines of the following will compile and run your project:
FROM winamd64/openjdk:7 COPY . /usr/src/myapp WORKDIR /usr/src/myapp RUN javac Main.java CMD ["java", "Main"]
You can then run and build the Docker image:
$ docker build -t my-java-app . $ docker run -it --rm --name my-running-app my-java-app
Compile your app inside the Docker container
There may be occasions where it is not appropriate to run your app inside a container. To compile, but not run your app inside the Docker instance, you can write something like:
$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp winamd64/openjdk:7 javac Main.java
This will add your current directory as a volume to the container, set the working directory to the volume, and run the command
javac Main.java which will tell Java to compile the code in
Main.java and output the Java class file to
Make JVM respect CPU and RAM limits
On startup JVM tries to detect the number of available CPU cores and the amount of RAM to adjust its internal parameters (like the number of garbage collector threads to spawn) accordingly. When container is run with limited CPU/RAM, standard system API, used by JVM for probing, will return host-wide values. This can cause excessive CPU usage and memory allocation errors with older versions of JVM.
Inside Linux containers, recent versions of OpenJDK 8 can correctly detect container-limited number of CPU cores by default. To enable the detection of container-limited amount of RAM the following options can be used:
$ java -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap ...
Inside Windows Server (non-Hyper-V) containers, limit for number of available CPU cores does not work (is ignored by Host Compute Service). To set such limit manually, JVM can be started the following way:
$ start /b /wait /affinity 0x3 path/to/java.exe ...
In this example CPU affinity hex mask
0x3 will limit JVM to 2 CPU cores.
RAM limit is supported by Windows Server containers, but currently JVM cannot detect it. To prevent excessive memory allocations,
-XX:MaxRAM=... option must be specified with the value that is not bigger than a containers RAM limit.
Environment variables with periods in their names
Some shells (notably, the BusyBox
/bin/sh included in Alpine Linux) do not support environment variables with periods in the names (which are technically not POSIX compliant), and thus strip them instead of passing them through (as Bash does). If your application requires environment variables of this form, either use
CMD ["java", ...] directly (no shell), or (install and) use Bash explicitly instead of
View license information for the software contained in this image.
As with all Docker images, these likely also contain other software which may be under other licenses (such as Bash, etc from the base distribution, along with any direct or indirect dependencies of the primary software being contained).
Some additional license information which was able to be auto-detected might be found in the
As for any pre-built image usage, it is the image user's responsibility to ensure that any use of this image complies with any relevant licenses for all software contained within.