How to use the command update-alternatives --config java

Question

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

User · Answer

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

User · Answer

This is how I install jdk     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

User · Answer

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 --config option  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 in   auto mode  You will need to use the --auto option in order to return   to the automatic state    And I believe auto mode is set when you install the first only JRE JDK

User · Answer

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

User · Answer

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

User · Answer

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 - gt   etc alternatives javac    ls -l  etc alternatives javac lrwxrwxrwx 1 root root 32 Sep  4 17 10  etc alternatives javac - gt   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

User · Answer

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    Installation  Install every java version in  opt java  lt version gt   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    gt  gt  environment sh    Log Out or restart Ubuntu  this will reload  etc profile d environment sh   Usage  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  lt enter gt  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  amp  amp  java -version  amp  amp  javac -version    Now use the change-java-version command to change java version

User · Answer

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

[java] How to use the command update-alternatives --config java

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