I am installing Apache Solr on Linux Debian (Squeeze). I have been instructed to install sun-java jdk 1st. Then am told that I should use the command sudo update-alternatives --config java to make sure that a particular java (sun-java) is the default runtime. Yet when I run this command I get:
There are 3 choices for the alternative java (providing /usr/bin/java).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/lib/jvm/java-6-openjdk/jre/bin/java 1061 auto mode
1 /usr/bin/gij-4.4 1044 manual mode
2 /usr/lib/jvm/java-6-openjdk/jre/bin/java 1061 manual mode
3 /usr/lib/jvm/java-6-sun/jre/bin/java 63 manual mode
Press enter to keep the current choice[*], or type selection number:
So which number should I select to have sun-java as the default runtime? Also, what exactly do th auto and manual modes mean? If I select 3 above and run the update-alternative command I receive the same output as above, again nothing seems to have changed except that the * is now in front of the 3, though it still reads manual mode.
Is there a way to confirm that what I have done is correct?
I'm using Ubuntu 18.04 LTS. Most of the time, when I change my java version, I also want to use the same javac version.
I use update-alternatives this way, using a java_home alternative instead :
Install every java version in /opt/java/<version>, for example
~$ ll /opt/java/
total 24
drwxr-xr-x 6 root root 4096 jan. 22 21:14 ./
drwxr-xr-x 9 root root 4096 feb. 7 13:40 ../
drwxr-xr-x 8 stephanecodes stephanecodes 4096 jan. 8 2019 jdk-11.0.2/
drwxr-xr-x 7 stephanecodes stephanecodes 4096 dec. 15 2018 jdk1.8.0_201/
Configure alternatives
~$ sudo update-alternatives --install /opt/java/current java_home /opt/java/jdk-11.0.2/ 100
~$ sudo update-alternatives --install /opt/java/current java_home /opt/java/jdk1.8.0_201 200
Declare JAVA_HOME (In this case, I use a global initialization script for this)
~$ sudo sh -c 'echo export JAVA_HOME=\"/opt/java/current\" >> environment.sh'
Log Out or restart Ubuntu (this will reload /etc/profile.d/environment.sh)
Change java version
Choose the version you want to use
~$ sudo update-alternatives --config java_home
There are 2 choices for the alternative java_home (providing /opt/java/current).
Selection Path Priority Status
------------------------------------------------------------
0 /opt/java/jdk-11.0.2 200 auto mode
1 /opt/java/jdk-11.0.2 200 manual mode
* 2 /opt/java/jdk1.8.0_201 100 manual mode
Press <enter> to keep the current choice[*], or type selection number:
Check version
~$ 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)
~$ javac -version
javac 11.0.2
Tip
Add the following line to ~/.bash_aliases file :
alias change-java-version="sudo update-alternatives --config java_home && java -version && javac -version"
Now use the change-java-version command to change java version
You will notice a big change when selecting options if you type in "java -version" after doing so. So if you run update-alternatives --config java and select option 3, you will be using the Sun implementation.
Also, with regards to auto vs manual mode, making a selection should take it out of auto mode per this page stating:
When using the
--configoption, alternatives will list all of the choices for the link group of which given name is the master link. You will then be prompted for which of the choices to use for the link group. Once you make a change, the link group will no longer be inauto mode. You will need to use the--autooption in order to return to the automatic state.
And I believe auto mode is set when you install the first/only JRE/JDK.
Assuming one has installed a JDK in /opt/java/jdk1.8.0_144 then:
Install the alternative for javac
$ sudo update-alternatives --install /usr/bin/javac javac /opt/java/jdk1.8.0_144/bin/javac 1
Check / update the alternatives config:
$ sudo update-alternatives --config javac
If there is only a single alternative for javac you will get a message saying so, otherwise select the option for the new JDK.
To check everything is setup correctly then:
$ which javac
/usr/bin/javac
$ ls -l /usr/bin/javac
lrwxrwxrwx 1 root root 23 Sep 4 17:10 /usr/bin/javac -> /etc/alternatives/javac
$ ls -l /etc/alternatives/javac
lrwxrwxrwx 1 root root 32 Sep 4 17:10 /etc/alternatives/javac -> /opt/java/jdk1.8.0_144/bin/javac
And finally
$ javac -version
javac 1.8.0_144
Repeat for java, keytool, jar, etc as needed.
If you want to switch the jdk on a regular basis (or update to a new one once it is released), it's very conveniant to use sdkman.
You can additional tools like maven with sdkman, too.
There are many other binaries that need to be linked so I think it's much better to try something like sudo update-alternatives --all and choosing the right alternatives for everything else besides java and javac.
Have a look at https://wiki.debian.org/JavaPackage At the bottom of this page an other method is descibed using a command from the java-common package
update-alternatives is problematic in this case as it forces you to update all the elements depending on the JDK.
For this specific purpose, the package java-common contains a tool called update-java-alternatives.
It's straightforward to use it. First list the JDK installs available on your machine:
root@mylaptop:~# update-java-alternatives -l
java-1.7.0-openjdk-amd64 1071 /usr/lib/jvm/java-1.7.0-openjdk-amd64
java-1.8.0-openjdk-amd64 1069 /usr/lib/jvm/java-1.8.0-openjdk-amd64
And then pick one up:
root@mylaptop:~# update-java-alternatives -s java-1.7.0-openjdk-amd64
#!/bin/bash
cd /opt/
sudo mkdir java
sudo tar -zxvf ~/Downloads/jdk-8u192-linux-x64.tar.gz
sudo ln -s jdk1.8.0_192 current
for file in /opt/java/current/bin/*
do
if [ -x $file ]
then
filename=`basename $file`
sudo update-alternatives --install /usr/bin/$filename $filename $file 20000
sudo update-alternatives --set $filename $file
#echo $file $filename
fi
done
Source: Stackoverflow.com