Date: 2015jul13 Product: Jetty OS: Linux Q. Why is Jetty giving NoClassDefFoundError exception on some pages after my webapp has run for a while? A. As you have probably read by now this error occurs when a class that existed at compile time can not be found at run time. Jetty unzips your .class files from your .war into /tmp/jetty* For me the problem was that tmpwatch would delete rarely used .class files from there after a while! The solution is easy once you know the problem. If you have /etc/tmpfiles.d ... Create /etc/tmpfiles.d/jetty and add: x /tmp/jetty* x /tmp/hsperfdata_* If you have /etc/cron.daily/tmpwatch.conf ... Add -X /tmp/jetty* (Notice that is an uppercase -X) Or change your Jetty configuration to unzip in a diffrent folder.