I'm stumped here. I got the same warning message and have followed the instructions found on the link [Java 21 upgrade instructions <https://www.jenkins.io/doc/book/platform-information/upgrade-java-to-21/>], but when I go to start Jenkins, it fails. The logs are not much help other than Jenkins failed to start. Using update-alternatives to set the JDK back to Ubuntu's OpenJDK-17-jdk, then Jenkins server starts as expected. Am I missing something here? Is there something wrong with my installation? I also tried Openjdk-21-jdk from Ubuntu default installation and I get the same issue: Jenkins fails to start.
Any help is appreciated. Kelly Holt On Tuesday, April 29, 2025 at 4:39:34 PM UTC-6 Kevin Martens wrote: > Hi Maciej, > > Thanks for raising this issue. I wanted to share that I've gone through > the jenkins.io documentation and believe I have created or updated all > the documentation spots for Java 21. This includes Java 21 upgrade > instructions > <https://www.jenkins.io/doc/book/platform-information/upgrade-java-to-21/>, > an update to the platform information page > <https://www.jenkins.io/doc/book/platform-information/> to include Java > 21, various installation documentation being updated to use images with > Java 21 such as Linux <https://www.jenkins.io/doc/book/installing/linux/> > and Docker <https://www.jenkins.io/doc/book/installing/docker/>, and any > area that would have previously used Java 17. If there are any other areas > of documentation that need to be updated accordingly, please let me know > and I'd be happy to make sure that everything is current. > > Thanks very much, > > Kevin Martens, Jenkins Documentation Officer > > On Thursday, April 10, 2025 at 6:34:22 AM UTC-4 maciej wrote: > >> Ullrich Hafner (2025-04-09 21:05): >> >> Yes, you are right. It makes sense to switch to Java 21 in the next >> couple of months (actually I never understood why one should not directly >> move from Java 11 to Java 21 for the controllers, as we also fully support >> Java 21 from the beginning of the Java 17 switch). The plan is to switch >> the weekly Jenkins releases to Java 21 in the middle of this year. >> See >> https://www.jenkins.io/blog/2023/11/06/introducing-2-2-2-java-support-plan/ >> >> If you find such wrong references of the Java version in out >> documentation it would be helpful if you can either create an issue in Jira >> or even better: click the „Improve the page“ button and fix the >> corresponding page by yourself. This helps us a lot as the documentation is >> spread along a lot of different files... >> >> >> The link does explain a bit, thanks. It talks about dropping JDK11, >> though. >> >> As for the docs updates, I really don't know what problems come with the >> upgrade, so I can't write about that. Should I expect everything to just >> work? Will all plugins work? Is there a tester script for this? Are popular >> plugins tested with various versions of Java automatically? >> >> I saw the video on upgrading to JDK17 (linked in the docs >> <https://www.jenkins.io/doc/book/platform-information/upgrade-java-to-17/index.html>), >> >> and it just talks about how to check my Java version and how to make sure >> the main node and builder nodes use the same Java version (which is helpful >> but doesn't explain much). It does seem like a very manual process to >> verify the upgrade. >> >> Cheers, >> Maciej Nux >> > -- You received this message because you are subscribed to the Google Groups "Jenkins Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/jenkinsci-users/c61cacaa-2b22-453f-a6c7-a43b78803cffn%40googlegroups.com.
