Introduction
After checking your Java Environment, downloaded and installed either an Oracle JDK or an Open JDK, now it's time to pack everything together.
At this point, you have a JVM installed below your /usr/lib/jvm directory and you've a jinfo file tuned to your needs with a unique priority number.
InstallNow it's time to link /etc/alternatives with our new installed JVM.
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Command LineUsually one has to install each java commands, tools or libraries one by one with the following interactive command:
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sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/default-java/jre/bin/java" 1073; |
Check if your added JVM java command has been processed by running:
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user@machine:~$ update-alternatives --list java
/usr/lib/jvm/default-java/jre/bin/java
/usr/lib/jvm/java-8-openjdk-i386/jre/bin/java
/usr/lib/jvm/java-8-oracle/jre/bin/java
/usr/lib/jvm/ramdisk-java-8-oracle/jre/bin/java |
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Scripting
Doing this task one by one is pretty tedious, we provide a shell script ito facilitate the work.
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This shell script mirror the content of the jinfo file described in the Java Environment Tutorial.
This shell script file contains various known plugins. However at this time we only describe the Firefox Java plugin support. It is why we suggest the other plugin support as comments.
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user@machine:/usr/lib/jvm/tools$ sudo update-java-alternatives -s default-java
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/appletviewer for appletviewer not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/extcheck for extcheck not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/idlj for idlj not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jarsigner for jarsigner not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jar for jar not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/javac for javac not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/javadoc for javadoc not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/javafxpackager for javafxpackager not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/javah for javah not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/javapackager for javapackager not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/javap for javap not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jcmd for jcmd not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jconsole for jconsole not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jdb for jdb not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jdeps for jdeps not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jhat for jhat not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jinfo for jinfo not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jmap for jmap not registered; not setting
update-alternatives: error: alternative /usr/lib/jvm/ramdisk-java-8-oracle/bin/jmc for jmc not registered; not setting
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In our configuration .default-java.jinfo refers to .ramdisk-java-8-oracle.jinfo:
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user@machine:/usr/lib/jvm$ ls -al .default-java.jinfo
lrwxrwxrwx 1 root root 30 Jul 12 14:29 .default-java.jinfo -> ./.ramdisk-java-8-oracle.jinfo |
The .default-java.jinfo is linked to .ramdisk-java-8-oracle.jinfo who use ramdisk-java-8-oracle as its name. This the reason why the previous command failed.
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name=ramdisk-java-8-oracle
priority=1073
section=main |
It means that ramdisk-java-8-oracle should be installed through the Update Alternatives mechanism before we can set the alternatives to default-java or you define a jinfo file with a different priority number.
Then check again that everything is correct with your Java Update Alternatives Environment.
UninstallNow it's time to unlink /etc/alternatives with the JVM we want to uninstall.
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Command LineUsually one has to uninstall each java commands, tools or libraries one by one with the following interactive command:
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sudo update-alternatives --remove "java" "/usr/lib/jvm/default-java/jre/bin/java"; |
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Scripting
Doing this task one by one is pretty tedious, we provide a shell script ito facilitate the work.
...
This shell script mirror the content of the jinfo file described in the Java Environment Tutorial.
This shell script file contains various known plugins. However at this time we only describe the Firefox Java plugin support. It is why we suggest the other plugin support as comments.
...
Then check again that everything is correct with your Java Update Alternatives Environment.