Hi,
I'm thinking of switching to Fedora 30
Silverblue(once it comes out of beta anyway) from
Arch linux. One of the requirements is to be able to
install, compile from source and easily switch
between JDK builds. However, Fedora fails to meet
these requirements so badly I'm fairly certain
whoever packaged and approved the various Java RPMs
was on shrooms(partial offense, sorry but this is
nuts).
Confused? Never installed Java in Fedora before?
Lets go down the rabbit hole together!
Firstly, the java version installed by doing:
rpm-ostree install java
gets you Java 8. I understand that Red Hat is
providing support until sometime 2023 however I feel
it to be much more appropriate that this either
gives the latest LTS(11 currently) or the newest
JDK(12 currently). Even if still technically
support, installing a JRE that old isn't likey to be
advised. Even in Ubuntu 18.10 you get Java 11.
OK, so just specify the specific versions that
you actually need and everything will work as it
should. No big deal, right? Nope.
alternatives(see:
https://fedoraproject.org/wiki/Java),
which is supposed to allow you to switch between
Java versions, flat out doesn't work. You tell it to
list all alternatives like so:
alternatives --display java
and the command executes without printing
anything. Odd. Let's just check what's in
/usr/lib/jvm for a sanity check:
ls /usr/lib/jvm
java-11-openjdk-11.0.2.7-7.fc30.x86_64
java-12-openjdk-12.0.0.33-1.ea.1.rolling.fc30.x86_64
java-1.8.0-openjdk-1.8.0.201.b09-6.fc30.x86_64
jre
jre-11
jre-11-openjdk
jre-11-openjdk-11.0.2.7-7.fc30.x86_64
jre-12
jre-12-openjdk
jre-12-openjdk-12.0.0.33-1.ea.1.rolling.fc30.x86_64
jre-1.8.0
jre-1.8.0-openjdk
jre-1.8.0-openjdk-1.8.0.201.b09-6.fc30.x86_64
jre-openjdk
...
What. I only installed Java 8, Java 11, and Java
12. Installing Java on either Ubuntu and Arch
doesn't duplicate any JRE/JDK like this.
OK, so lets open it in nautilus:
nautilus /usr/lib/jvm
Those aren't duplicates, all but 3 folders are
system links? What? This should be the one and only
system location for JRE/JDK(s). What's going on
here? Where do they go?
They go to /etc/alternatives. I guess this is
supposed to be how alternatives finds alternative
JRE/JDK installs. Ubuntu doesn't have to do this for
update-alternatives nor does Arch's archlinux-_javascript_ but... OK. This is insanely complicated for
no real good reason.
But wait, we aren't done yet because what's being
linked to from /usr/lib/jvm isn't a file, it's...
another system link. Back to the 3 non system links
in /usr/lib/jvm which have horrendously long and
complex folder names. Is calling them
java-<version>-<jre/jdk>-<oracle/zulu/openjdk>
not enough?
To top this "what" fest off, the JRE/JDK folders
in /etc/alternatives aren't even named properly.
That is to say, "jre" is attached to the front
even if what's being linked is a JDK. Yes, a JDK
contains a JRE but it's still horribly confusing for
no good reason. Like, imagining if alternatives did
work, does it list duplicate entries for each
JRE/JDK? For example:
jre_11
java-11-openjdk
which(again) system link to the same JDK install.
What shroom induced insanity is this? Why does
alternatives not work?
