Debian Wheezy and the openjdk-6-* package

Question

I was fiddling around on Minecraft a moment ago and noticed something strange - It was using OpenJDK 6 (at least for my profile, I don't know what the launcher is using...), which I didn't realize was installed by default. (Of course I should've realized this, I believe Libre Office uses it...Java, that is.)

I usually install the openjdk-7-jre package when setting up my system after a fresh installation.

Is there a reason to keep OpenJDK 6 around? If not, how does one remove it entirely? I tried a simple apt-get autoremove openjdk-6-jre, but that also wanted to remove default-jre , and I don't know what that is or does exactly.

I tested Minecraft with OpenJDK 7, everything seemed just fine!

If it is required to keep it, is there a way to make OpenJDK 7 default for everything else that doesn't require OpenJDK 6?

Update:

I did some more searching and found this.

update-alternatives --config java

There are 2 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      auto mode
  1            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      manual mode
  2            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1051      manual mode

Press enter to keep the current choice[*], or type selection number:

I selected "2" and hit enter.

which java

This only gave me the output /usr/bin/java, not which version it was technically using like the post had said it should.

I also opened Libre Office for fun and looked in the options - It has the option to change which JDK to use, so I swapped that to version 7 as well.

So the question still remains, is OpenJDK 6 required to keep, or can it be removed in place of OpenJDK 7? If I can remove it, how would I go about removing it entirely?

Answer 1

Debian use update-alternative to allow to easily change between various versions of a given program.

take a look at /usr/bin/java

# ls -l /usr/bin/java
lrwxrwxrwx 1 root root 22 janv. 19 23:12 /usr/bin/java -> /etc/alternatives/java

This is a link to /etc/alternatives/java:

# ls -l /etc/alternatives/java
lrwxrwxrwx 1 root root 45 janv. 19 23:12 /etc/alternatives/java -> /usr/lib/jvm/java-6-openjdk-i386/jre/bin/java

As you see, on my system, i use java-6-openjdk-i386 as my JRE.

take a look on your system at the result of :

readlink -f /usr/bin/java

This command show you the real binary used when you call java.

As for removing openjdk-6, you can safely do it. The package default-jre is just a "dummy" package containing nothing but a dependency to openjdk 6. It is used to ease the installation of Java.