From: http://scmlife.com/thread-31073-1-1.html
工作中要安裝一個插件但當前jenkins版本過低，在scmlife搜索了下沒有jenkins升級相關資料，今天升級後特意做下記錄分享給我大家，記錄比較詳細，高手就飄過吧 。爲避免不必要的麻煩，以下請在Jenkins Home機器進行操作：
1.在jenkins系統設置界面發現類似如下提示：New version of Jenkins (1.500) is available for download (changelog).下載最新版本jenkins.war
2.[scm@Linux jenkins]$ ps -aux | grep jenkins #查看jenkins安裝路徑，下方紅色字體
...
jenkins 19139 30.8 7.0 1496412 273816 ? Ssl 15:24 11:18 /usr/lib/jvm/jre-1.6.0/bin/java -Dcom.sun.akuma.Daemon=daemonized -Djava.awt.headless=true -DJENKINS_HOME=/var/lib/jenkins -jar/usr/lib/jenkins/jenkins.war --logfile=/var/log/jenkins/jenkins.log --webroot=/var/cache/jenkins/war --daemon --httpPort=8888 --ajp13Port=8009 --debug=5 --handlerCountMax=100 --handlerCountMaxIdle=20
...
3.[scm@Linux jenkins]$cd /usr/lib/jenkins/ #進入jenkins目錄，建議此時備份原來的jenkins.war
4.[scm@Linux jenkins]$sudo rcjenkins stop #關閉jenkins服務
5.[scm@Linux jenkins]sudo cp -i /home/scm/public/jenkins.war ./ #覆蓋原因來jenkins
6.[scm@Linux jenkins]sudo rcjenkins start #啓動jenkins服務)
7.好了，升級ok,可以看到版本已升級到最新了，但是此時管理界面出現了一些提示：
Because of a security vulnerability discovered earlier, we need to change the encryption key used to protect secrets in your configuration files on the disk. This process scans a large portion of your $JENKINS_HOME (/var/lib/jenkins), find encrypted data, re-key them, which will take some time. See this document for more implications about different ways of doing this (or not doing this.) This operation can be safely run in background, but cautious users are recommended to take backups.3 R* }/
單擊 “Re-key in background now”按鈕即對整個Jenkins Home進行校驗，一般需要1-2天的時間。可以在日誌裏查看進度。