How to install openjdk-8-jdk on Debian 10 (Buster)?

Question

It seems Debian does not support openjdk-8-jdk anymore due to a security issue. What is the easiest way to install openjdk-8-jdk for Debian 10 (Buster)?

Answer 1

You can search the Debian packages site and find out the openjdk-8-jdk package for Debian 10 is only available from unstable (sid) repository currently.

At first it is good to check and save current system-wide symbolic links for already installed Java SDK/JRE packages if any:

ls -la /etc/alternatives | grep java > previous-java-alternatives.txt

Then check is this package can be installed with current configuration:

apt-cache policy openjdk-8-jdk

If no then you need to add unstable repository to the sources list. The negative output may imply that you prefer to use stable repositories and usually it isn't appropriate for you to update all other software from unstable repositories. So before adding unstable repository to the sources list make sure APT::Default-Release configuration option is set to "stable":

grep -r Default-Release /etc/apt/

If no (as by default) then set it as recommended in that answer by creating this file:

/etc/apt/apt.conf.d/99defaultrelease

APT::Default-Release "stable";

Now you're ready to add the unstable repository to the sources list. Before I prefer to check what mirror was selected by me when system was installed. Just look to main sources list:

cat /etc/apt/sources.list

In my case the output shows that mirror.yandex.ru server is used as system source. So I use the same for unstables and add this file:

/etc/apt/sources.list.d/91-debian-unstable.list

deb http://mirror.yandex.ru/debian/ unstable main
deb-src http://mirror.yandex.ru/debian/ unstable main

(I also have 90-debian-testing.list file for the testing repo.)

Then update package lists:

apt update

And check you system wont update from unstable sources:

apt list --upgradable

And recheck is required package can be installed:

apt-cache policy openjdk-8-jdk

Do install the package:

apt install openjdk-8-jdk

Look at new symbolic links:

ls -la /etc/alternatives | grep java-8

Just waste few seconds on them (or continue with man 1 update-alternatives).