I have already set up an java environment but it cannot active the jenkins. I really need help. I’m using ubuntu server 20.04 . Thanks alot
The Jenkins documentation suggests:
journalctl -u jenkins
so that the output is specific to Jenkins.
Ubuntu 20.04 will no longer be supported by Jenkins after the end of Ubuntu public support 2 Apr 2025. You should either install on a newer operating system or plan now to replace that operating system within the next 6 months.