Confluence won't start due to error could not find the main class program will exit because of a syntax problem in Setenv file
Confluence fails to start.
Could not find the main class: Xms256m. Program will exit. Exception in thread "main" java.lang.NoClassDefFoundError: Xms256m Caused by: java.lang.ClassNotFoundException: Xms256m
Confluence fails to start due to some incorrect parameters in tomcat configuration files such as setenv.sh or bat file.
In the message above we can see the part where the Xms256m is stated. This part can be different depending on the incorrect syntax.
Open the setenv.sh or bat file (depending on the OS) and check for syntax errors. In the case above, the problem was a missing dash ( - ) in front of the Xms256m word. Compare the file with a standard one if necessary.