update-alternatives and default-java symbolic link (on Debian 10 Buster)

supermario18b · 10-09-2019, 10:38 AM

Hi everyone,

I noticed that when I use the command "update-alternatives" to change the default java version the "default-java" symbolic link in /usr/lib/jvm doesn't change. It still points to the old default java version. Why?

Everything works fine, if I type "java -version" on terminal it shows the desired java version. Only the symbolic link doesn't change.

Shouldn't it change?

ondoho · 10-10-2019, 02:20 PM

show us the full output of all commands that led to your conclusion.

supermario18b · 10-12-2019, 09:13 AM

Quote:

Originally Posted by ondoho

show us the full output of all commands that led to your conclusion.

Hi, here is the output with java11 as default:

Code:

------------------------------------------------------------
  0            /usr/lib/jvm/java-11-openjdk-amd64/bin/java   1111      
* 1            /opt/jdk11/bin/java                           3         
  2            /opt/jdk12/bin/java                           4         
  3            /opt/jdk8/bin/java                            1         
  4            /usr/lib/jvm/java-11-openjdk-amd64/bin/java   1111

the java -version is right:

Code:

root@debian:~# java -version
openjdk version "11.0.2" 2019-01-15
OpenJDK Runtime Environment 18.9 (build 11.0.2+9)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.2+9, mixed mode)

so it works and the default link is right:

Code:

root@debian:~# ls -l /usr/lib/jvm/
lrwxrwxrwx 1 root root   25 dec 30  2018 default-java -> java-1.11.0-openjdk-amd64
lrwxrwxrwx 1 root root   21 jun 16 20:24 java-1.11.0-openjdk-amd64 -> java-11-openjdk-amd64
drwxr-xr-x 7 root root 4096 aug  9 07:22 java-11-openjdk-amd64

Now I switch to java 8 with "update-alternatives --config java" and here is the output:

Code:

------------------------------------------------------------
  0            /usr/lib/jvm/java-11-openjdk-amd64/bin/java   1111      
  1            /opt/jdk11/bin/java                           3         
  2            /opt/jdk12/bin/java                           4         
* 3            /opt/jdk8/bin/java                            1         
  4            /usr/lib/jvm/java-11-openjdk-amd64/bin/java   1111

The java version is right:

Code:

root@debian:~# java -version
openjdk version "1.8.0_222"
OpenJDK Runtime Environment (AdoptOpenJDK)(build 1.8.0_222-b10)
OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.222-b10, mixed mode)

So it works but the java default link still points to the version 11 of java:

Code:

root@debian:~# ls -l /usr/lib/jvm/
lrwxrwxrwx 1 root root   25 dec 30  2018 default-java -> java-1.11.0-openjdk-amd64
lrwxrwxrwx 1 root root   21 jun 16 20:24 java-1.11.0-openjdk-amd64 -> java-11-openjdk-amd64
drwxr-xr-x 7 root root 4096 aug  9 07:22 java-11-openjdk-amd64

ondoho · 10-13-2019, 04:21 AM

I think the other java versions should be listed in /usr/lib/jvm/ as well.
How did you install them? Seems strange, to /opt.

supermario18b · 10-13-2019, 07:25 AM

I've manually installed (copied) the other java version in /opt. I just tried to install that in /usr/lib/jvm and I can switch between java versions but the symbolic link still only points to a java version.

ondoho · 10-14-2019, 01:58 AM

Quote:

Originally Posted by supermario18b

I've manually installed (copied) the other java version in /opt. I just tried to install that in /usr/lib/jvm and I can switch between java versions but the symbolic link still only points to a java version.

So you completely circumvented APT package management to install various java versions.
Since update-alternatives is an APT thing, I'm not surprised it doesn't work.

supermario18b · 10-14-2019, 11:05 AM

You mean that if I would have installed the various java versions with APT, the default-java link would have been changed too.
Is it important? I mean, I noticed that the symbolic link doesn't change but everything works fine (the switch works fine). Has this default-java link some other function/implication?