首先吐槽一下Jenkins：
1、安装插件的时候无法根据Jenkins的版本号安装对应的插件！
2、安装插件安装版本不一致的时候无法降低插件版本！
3、为啥要我们升级到最新版！
一、升级原因
我的Jenkins提示一堆插件不符合版本要求，无法使用，去插件网站下载低版本的插件发现也是无法解决，最后迫不得已只能升级Jenkins。垃圾Jenkins！
二、说明
因为我是通过yum安装的Jenkins，没升级之前 使用systemctl start jenkins 都没问题。
Jenkins 从2.300 升级到最新版2.340，使用systemctl start jenkins 一直卡住，但是在另外的终端查看是有Jenkins进程启动的，只是和原来的进程不一样。
正常的情况下之后下面红框的进程，明显是多了两个进程：
systemctl start jenkins 卡了很久之后，然后下面报错：
Mar 25 15:50:54 gogslfs.leniu.com polkitd[599]: Registered Authentication Agent for unix-process:17645:1020038543 (system bus name :1.
Mar 25 15:50:54 gogslfs.leniu.com systemd[1]: Stopping LSB: Jenkins Automation Server...
-- Subject: Unit jenkins.service has begun shutting down
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit jenkins.service has begun shutting down.
Mar 25 15:50:55 gogslfs.leniu.com jenkins[17651]: Shutting down Jenkins [ OK ]
Mar 25 15:50:55 gogslfs.leniu.com systemd[1]: Stopped LSB: Jenkins Automation Server.
-- Subject: Unit jenkins.service has finished shutting down
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit jenkins.service has finished shutting down.
Mar 25 15:50:55 gogslfs.leniu.com polkitd[599]: Unregistered Authentication Agent for unix-process:17645:1020038543 (system bus name :
Mar 25 15:51:19 gogslfs.leniu.com polkitd[599]: Registered Authentication Agent for unix-process:17671:1020041100 (system bus name :1.
Mar 25 15:51:19 gogslfs.leniu.com systemd[1]: Starting LSB: Jenkins Automation Server...
-- Subject: Unit jenkins.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit jenkins.service has begun starting up.
Mar 25 15:51:19 gogslfs.leniu.com runuser[17678]: pam_unix(runuser:session): session opened for user root by (uid=0)
Mar 25 15:51:24 gogslfs.leniu.com jenkins[17677]: Starting Jenkins WARNING: An illegal reflective access operation has occurred
Mar 25 15:51:24 gogslfs.leniu.com jenkins[17677]: WARNING: Illegal reflective access by org.codehaus.groovy.vmplugin.v7.Java7$1 (file:
Mar 25 15:51:24 gogslfs.leniu.com jenkins[17677]: WARNING: Please consider reporting this to the maintainers of org.codehaus.groovy.vm
Mar 25 15:51:24 gogslfs.leniu.com jenkins[17677]: WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective
Mar 25 15:51:24 gogslfs.leniu.com jenkins[17677]: WARNING: All illegal access operations will be denied in a future release
Mar 25 15:56:19 gogslfs.leniu.com systemd[1]: jenkins.service start operation timed out. Terminating.
Mar 25 15:56:19 gogslfs.leniu.com systemd[1]: Failed to start LSB: Jenkins Automation Server.
-- Subject: Unit jenkins.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit jenkins.service has failed.
--
-- The result is failed.
Mar 25 15:56:19 gogslfs.leniu.com systemd[1]: Unit jenkins.service entered failed state.
Mar 25 15:56:19 gogslfs.leniu.com systemd[1]: jenkins.service failed.
Mar 25 15:56:19 gogslfs.leniu.com polkitd[599]: Unregistered Authentication Agent for unix-process:17671:1020041100 (system bus na但是是不影响Jenkins使用，也没有相关的日志报错。
而且kill掉上面三个进程之后，如果使用systemctl start jenkins 启动发现，发现没有卡住，也没有日志输出。而且是一下子就执行完了，但是实际上Jenkins没有启动。
解决方法：使用restart来启动（很狗）具体原因未知！！！！但是Jenkins能正常使用。
systemctl restart jenkins
