After JRuby 1.1RC2 it is no longer possible to deploy a JRuby on Rails application using the mongrel_jcluster gem. It appears that some key files such as jrubycli etc. are no longer included and were required by mongrel_jcluster. This is a big deal breaker for deployment since running on a single mongrel won't cut it, and I don't really want to move to something like glassfish. To reproduce issue the command: sudo jruby -S mongrel_rails jcluster::start I did not get a stack trace, but rather the following output: Starting JRuby server... Starting 4 Mongrel servers... sh: jrubycli: command not found mongrel_rails start -e production -p 8000 -a 127.0.0.1 -l /var/www/app/current/log/mongrel.log -P /var/www/app/current/tmp/pids/mongrel.8000.pid -c /var/www/app/current sh: jrubycli: command not found mongrel_rails start -e production -p 8001 -a 127.0.0.1 -l /var/www/app/current/log/mongrel.log -P /var/www/app/current/tmp/pids/mongrel.8001.pid -c /var/www/app/current sh: jrubycli: command not found mongrel_rails start -e production -p 8002 -a 127.0.0.1 -l /var/www/app/current/log/mongrel.log -P /var/www/app/current/tmp/pids/mongrel.8002.pid -c /var/www/app/current sh: jrubycli: command not found mongrel_rails start -e production -p 8003 -a 127.0.0.1 -l /var/www/app/current/log/mongrel.log -P /var/www/app/current/tmp/pids/mongrel.8003.pid -c /var/www/app/current I tried copying the jrubycli from an old release to the JRuby 1.1 final but further errors were encountered. Issue JRUBY-983 appears to be related: http://jira.codehaus.org/browse/JRUBY-983 Thanks, Brandon Hauff