Problem changing Java version using alternatives

Question

I\'m not quite sure how I got into this mess, but for some reason I\'m not able to change the current version of Java using alternatives. I can run alternatives --config java a

Answer 1

When using the alternatives method, if you want to use an alternative, it must first be installed. I believe RPMs would include this as a part of the install, but in the case where manual installs are performed, you can still manually install. For example, with java,

alternatives --install "/usr/bin/java" "java" "/usr/java/example/bin/java" \
 --slave /usr/bin/javac javac /usr/java/example/bin/javac \
 ...

What this does is to install an alternative for the java symlink. For each slave, it also builds/updates the symlink to some other value specified in another alternative, when you switch it. So if you were to switch to a different version of java using alternatives, and the alternative specifies a slave for javac, javac will repoint to the new version as well.

My full list is as follows:

alternatives --install /usr/bin/java java /usr/java//bin/java 1500 \
  --slave /usr/bin/ControlPanel ControlPanel /usr/java//jre/bin/ControlPanel \
   --slave /usr/bin/jar jar /usr/java//bin/jar \
   --slave /usr/bin/javac javac /usr/java//bin/javac \
   --slave /usr/bin/javaws javaws /usr/java//bin/javaws \
   --slave /usr/bin/jcontrol jcontrol /usr/java//bin/jcontrol \
   --slave /usr/bin/keytool keytool /usr/java//bin/keytool \
   --slave /usr/bin/orbd orbd /usr/java//bin/orbd \
   --slave /usr/bin/pack200 pack200 /usr/java//bin/pack200 \
   --slave /usr/bin/policytool policytool /usr/java//bin/policytool \
   --slave /usr/bin/rmid rmid /usr/java//bin/rmid \
   --slave /usr/bin/rmiregistry rmiregistry /usr/java//bin/rmiregistry \
   --slave /usr/bin/servertool servertool /usr/java//bin/servertool \
   --slave /usr/bin/tnameserv tnameserv /usr/java//bin/tnameserv \
   --slave /usr/bin/unpack200 unpack200 /usr/java//bin/unpack200 \
   --slave /usr/share/man/man1/java.1 java.1 /usr/java//man/man1/java.1  \ 
   --slave /usr/share/man/man1/javac.1 javac.1 /usr/java//man/man1/javac.1  \ 
   --slave /usr/share/man/man1/javaws.1 javaws.1 /usr/java//man/man1/javaws.1  \ 
   --slave /usr/share/man/man1/keytool.1 keytool.1 /usr/java//man/man1/keytool.1  \ 
   --slave /usr/share/man/man1/orbd.1 orbd.1 /usr/java//man/man1/orbd.1  \ 
   --slave /usr/share/man/man1/pack200.1 pack200.1 /usr/java//man/man1/pack200.1  \ 
   --slave /usr/share/man/man1/policytool.1 policytool.1 /usr/java//man/man1/policytool.1  \ 
   --slave /usr/share/man/man1/rmid.1 rmid.1 /usr/java//man/man1/rmid.1  \ 
   --slave /usr/share/man/man1/rmiregistry.1 rmiregistry.1 /usr/java//man/man1/rmiregistry.1  \ 
   --slave /usr/share/man/man1/servertool.1 servertool.1 /usr/java//man/man1/servertool.1  \ 
   --slave /usr/share/man/man1/tnameserv.1 tnameserv.1 /usr/java//man/man1/tnameserv.1  \ 
   --slave /usr/share/man/man1/unpack200.1 unpack200.1 /usr/java//man/man1/unpack200.1

Hope this helps.