Installing OpenJDK 16 on Raspberry Pi 4

Question

I am trying to install OpenJDK 16 on my Raspberry Pi 4. I'm running a minecraft server and there was an update recently which requires Java 16, but I have Java 8 installed. There is no openjdk-16-jdk package so I downloaded the tar file for Linux / AArch64 as the Pi has an ARM processor. I then followed these instructions to install it. When I try to run java -version, I get this error:

bash: /usr/bin/java: cannot execute binary file: Exec format error

It appears this is the wrong version, but neither of the Linux downloads on the website worked, so I'm not sure what is wrong. Here's a bit of system information in case it's useful:
Linux raspberrypi 5.10.17-v7l+ #1403 SMP Mon Feb 22 11:33:35 GMT 2021 armv7l GNU/Linux
And these are the options for sudo update-alternatives --config java:

Selection    Path                                             Priority   Status
------------------------------------------------------------
  0            /usr/lib/jvm/java-1.16.0-openjdk-armhf/bin/java   1131      auto mode
* 1            /usr/lib/jvm/java-1.16.0-openjdk-armhf/bin/java   1131      manual mode
  2            /usr/lib/jvm/java-1.8.0-openjdk-armhf/bin/java    1131      manual mode
  3            /usr/lib/jvm/java-8-openjdk-armhf/jre/bin/java    1081      manual mode

Answer 1

I wrestled with the same issue a few days ago.

I have been running a Minecraft server on a Raspberry Pi 4, using Java 8, installed via sudo apt install openjdk-8-jdk.

However, as of snapshot 21w19a, which was a few snapshots before the 1.17 release, Java 16 has become the minimum for Minecraft.

The Java 16 binary in the openjdk-16.0.1_linux-aarch64_bin.tar.gz file I downloaded from http://jdk.java.net/16/ gives an error when run on my Raspberry Pi 4:

$ ./jdk-16.0.1/bin/java --version
-bash: ./jdk-16.0.1/bin/java: cannot execute binary file: Exec format error

If we use file on that binary, we can see a bit more detail:

$ file ./jdk-16.0.1/bin/java
./jdk-16.0.1/bin/java: ELF 64-bit LSB shared object, ARM aarch64,
version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64.so.1,
for GNU/Linux 3.7.0, not stripped

Note "64-bit" and "ARM aarch64".

Compare this with the working Java 8 binary I have - note "32-bit" here:

$ file /usr/lib/jvm/java-8-openjdk-armhf/jre/bin/java
/usr/lib/jvm/java-8-openjdk-armhf/jre/bin/java: ELF 32-bit LSB executable, ARM,
EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3,
for GNU/Linux 3.2.0, BuildID[sha1]=6d2781f51a497603976e8fee28b888bd771fd5b7, stripped

I believe (I'm no expert) that the Raspberry Pi 4 CPU is able to run aarch64 code, but the current default OS doesn't support it.

$ uname -a
Linux [name] 5.10.17-v7l+ #1414 SMP Fri Apr 30 13:20:47 BST 2021 armv7l GNU/Linux

There, note armv7l.

This article - "How to Make Your Raspberry Pi 4 Faster with a 64 Bit Kernel" helped me to understand a little more. If I read that right, although we could edit /boot/config.txt to include the arm_64bit=1, that would give us a 64 bit kernel, but not the ability to run 64 bit aarch64 binaries, because we still have a 32 bit userland. (If I've misunderstood here, I'd appreciate if someone could correct me so I can learn.)

So, summary so far: Oracle supply a Java 16 JDK at jdk.java.net, but the only ARM binary there is aarch64. I think this may be supported by the processor on the Raspberry Pi 4, but not by the default OS.

Luckily, AdoptOpenJDK (run by a community of Java User Group members, including some big names) seem to make a wider variety of Java binaries available for download.

I went to https://adoptopenjdk.net/releases.html and made the following choices:

• Version: OpenJDK 16 (Latest)

  • Chose because Java 16 is the minimum for Minecraft 1.17 (see top of post).
  • Note this isn't a "Long Term Support" (LTS) version. This Minecraft Paper server post about Java 16 explains more.

• JVM: HotSpot

  • The alternative option here is OpenJ9, but I believe that Mojang ship and test Minecraft with the HotSpot JVM, so that's what I chose.

• Operating System: Linux

• Architecture: arm32

  • Not aarch64: see above

• JDK or JRE: JRE

  • To run Minecraft, all we need is a java binary. So the Java Runtime Environment (JRE) is fine. The Java Development Kit (JDK) includes more tools, but the JRE is a smaller download and installation, so I went for that. See this question for more on JDK vs JRE.

Those choices have given me a working Java 16:

$ ./jdk-16.0.1+9-jre/bin/java -version
openjdk version "16.0.1" 2021-04-20
OpenJDK Runtime Environment AdoptOpenJDK-16.0.1+9 (build 16.0.1+9)
OpenJDK Server VM AdoptOpenJDK-16.0.1+9 (build 16.0.1+9, mixed mode)
$ file ./jdk-16.0.1+9-jre/bin/java
./jdk-16.0.1+9-jre/bin/java: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV),
dynamically linked, interpreter /lib/ld-linux-armhf.so.3, for GNU/Linux 3.2.0,
not stripped

... and this is working so far for me, in the limited testing I've done so far, with the vanilla 1.17 server JAR I downloaded from https://www.minecraft.net/en-us/download/server.

Answer 2

I did the following and it worked for me (To install openjdk 16 for minecraft 1.17.1):

First I downloaded any jdk by using:

sudo apt install openjdk-8-jdk

Then I downloaded this file and extracted it in a new folder under /usr/lib/jvm

After that I runned:

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/{name of the folder you just created}/bin/java 1131

And then I checked it was installed and selected by using:

sudo update-alternatives --config java

Answer 3

Because the JDK was 64-bit and the Pi is 32-bit, I had to get a 64-bit terminal by following this guide and doing the following:

1. sudo apt-get update and sudo apt-get -y upgrade to make sure everything is up to date
2. sudo apt-get install -y --no-install-recommends raspbian-nspawn-64 to install the 64-bit Debian Buster terminal
3. ds64-shell to launch the 64-bit shell
4. I used this SO answer to install java 8 in the 64-bit shell. From there I followed the same procedure as before to install java 16 and it worked.