I also have this problem, but I can figure out how to fix this because that file isn’t there.
Nov 08 15:36:56 blouinfe systemd[1]: Starting OpenNebula Web UI Server...
Nov 08 15:36:56 blouinfe systemd[1]: Started OpenNebula Web UI Server.
Nov 08 15:36:56 blouinfe ruby[5069]: /var/lib/gems/2.5.0/gems/rack-2.0.7/lib/rack/show_exceptions.rb:16: warning: already initialized constant Rack::ShowExceptions::CONTEXT
Nov 08 15:36:56 blouinfe ruby[5069]: /usr/lib/ruby/vendor_ruby/rack/showexceptions.rb:16: warning: previous definition of CONTEXT was here
Nov 08 15:36:56 blouinfe ruby[5069]: /var/lib/gems/2.5.0/gems/rack-2.0.7/lib/rack/show_exceptions.rb:114: warning: already initialized constant Rack::ShowExceptions::TEMPLATE
Nov 08 15:36:56 blouinfe ruby[5069]: /usr/lib/ruby/vendor_ruby/rack/showexceptions.rb:115: warning: previous definition of TEMPLATE was here
Nov 08 15:36:57 blouinfe ruby[5069]: --------------------------------------
Nov 08 15:36:57 blouinfe ruby[5069]: Server configuration
Nov 08 15:36:57 blouinfe ruby[5069]: --------------------------------------
Nov 08 15:36:57 blouinfe ruby[5069]: {:tmpdir=>"/var/tmp",
Nov 08 15:36:57 blouinfe ruby[5069]: :one_xmlrpc=>"http://localhost:2633/RPC2",
Nov 08 15:36:57 blouinfe ruby[5069]: :host=>"127.0.0.1",
Nov 08 15:36:57 blouinfe ruby[5069]: :port=>9869,
Nov 08 15:36:57 blouinfe ruby[5069]: :sessions=>"memory",
Nov 08 15:36:57 blouinfe ruby[5069]: :memcache_host=>"localhost",
Nov 08 15:36:57 blouinfe ruby[5069]: :memcache_port=>11211,
Nov 08 15:36:57 blouinfe ruby[5069]: :memcache_namespace=>"opennebula.sunstone",
Nov 08 15:36:57 blouinfe ruby[5069]: :debug_level=>3,
Nov 08 15:36:57 blouinfe ruby[5069]: :auth=>"opennebula",
Nov 08 15:36:57 blouinfe ruby[5069]: :core_auth=>"cipher",
Nov 08 15:36:57 blouinfe ruby[5069]: :vnc_proxy_port=>29876,
Nov 08 15:36:57 blouinfe ruby[5069]: :vnc_proxy_support_wss=>false,
Nov 08 15:36:57 blouinfe ruby[5069]: :vnc_proxy_cert=>nil,
Nov 08 15:36:57 blouinfe ruby[5069]: :vnc_proxy_key=>nil,
Nov 08 15:36:57 blouinfe ruby[5069]: :vnc_proxy_ipv6=>false,
Nov 08 15:36:57 blouinfe ruby[5069]: :lang=>"en_US",
Nov 08 15:36:57 blouinfe ruby[5069]: :table_order=>"desc",
Nov 08 15:36:57 blouinfe ruby[5069]: :marketplace_url=>"http://marketplace.opennebula.systems/appliance",
Nov 08 15:36:57 blouinfe ruby[5069]: :oneflow_server=>"http://localhost:2474/",
Nov 08 15:36:57 blouinfe ruby[5069]: :instance_types=>
Nov 08 15:36:57 blouinfe ruby[5069]: [{:name=>"small-x1", Nov 08 15:36:57 blouinfe ruby[5069]: :cpu=>1,
Nov 08 15:36:57 blouinfe ruby[5069]: :vcpu=>1, Nov 08 15:36:57 blouinfe ruby[5069]: :memory=>128,
Nov 08 15:36:57 blouinfe ruby[5069]: :description=>"Very small instance for testing purposes"}, Nov 08 15:36:57 blouinfe ruby[5069]: {:name=>“small-x2”,
Nov 08 15:36:57 blouinfe ruby[5069]: :cpu=>2, Nov 08 15:36:57 blouinfe ruby[5069]: :vcpu=>2,
Nov 08 15:36:57 blouinfe ruby[5069]: :memory=>512, Nov 08 15:36:57 blouinfe ruby[5069]: :description=>“Small instance for testing multi-core applications”},
Nov 08 15:36:57 blouinfe ruby[5069]: {:name=>"medium-x2", Nov 08 15:36:57 blouinfe ruby[5069]: :cpu=>2,
Nov 08 15:36:57 blouinfe ruby[5069]: :vcpu=>2, Nov 08 15:36:57 blouinfe ruby[5069]: :memory=>1024,
Nov 08 15:36:57 blouinfe ruby[5069]: :description=>"General purpose instance for low-load servers"}, Nov 08 15:36:57 blouinfe ruby[5069]: {:name=>“medium-x4”,
Nov 08 15:36:57 blouinfe ruby[5069]: :cpu=>4, Nov 08 15:36:57 blouinfe ruby[5069]: :vcpu=>4,
Nov 08 15:36:57 blouinfe ruby[5069]: :memory=>2048, Nov 08 15:36:57 blouinfe ruby[5069]: :description=>“General purpose instance for medium-load servers”},
Nov 08 15:36:57 blouinfe ruby[5069]: {:name=>"large-x4", Nov 08 15:36:57 blouinfe ruby[5069]: :cpu=>4,
Nov 08 15:36:57 blouinfe ruby[5069]: :vcpu=>4, Nov 08 15:36:57 blouinfe ruby[5069]: :memory=>4096,
Nov 08 15:36:57 blouinfe ruby[5069]: :description=>"General purpose instance for servers"}, Nov 08 15:36:57 blouinfe ruby[5069]: {:name=>“large-x8”,
Nov 08 15:36:57 blouinfe ruby[5069]: :cpu=>8, Nov 08 15:36:57 blouinfe ruby[5069]: :vcpu=>8,
Nov 08 15:36:57 blouinfe ruby[5069]: :memory=>8192, Nov 08 15:36:57 blouinfe ruby[5069]: :description=>“General purpose instance for high-load servers”}], Nov 08 15:36:57 blouinfe ruby[5069]: :routes=>[“oneflow”, “vcenter”, “support”]} Nov 08 15:36:57 blouinfe ruby[5069]: --------------------------------------
Nov 08 15:36:57 blouinfe ruby[5069]: /var/lib/gems/2.5.0/gems/rack-2.0.7/lib/rack/session/abstract
id.rb:202:in <class:Persisted>: uninitialized
constantRack::Session::Abstract::Persisted::RACK_SESSION (NameError)
Nov 08 15:36:57 blouinfe ruby[5069]: Did you mean? Rack::Session
Nov 08 15:36:57 blouinfe ruby[5069]: from /var/lib/gems/2.5.0/gems/rack-2.0.7/lib/rack/session/abstract/id.rb:200:in module:Abstract’ Nov 08 15:36:57 blouinfe ruby[5069]: from /var/lib/gems/2.5.0/gems/rack-2.0.7/lib/rack/session/abstract/id.rb:14:in <module:Session>'
Nov 08 15:36:57 blouinfe ruby[5069]: from /var/lib/gems/2.5.0/gems/rack-2.0.7/lib/rack/session/abstract/id.rb:12:in module:Rack’ Nov 08 15:36:57 blouinfe ruby[5069]: from /var/lib/gems/2.5.0/gems/rack-2.0.7/lib/rack/session/abstract/id.rb:10:in <top (required)>'
Nov 08 15:36:57 blouinfe ruby[5069]: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in require’ Nov 08 15:36:57 blouinfe ruby[5069]: from /var/lib/gems/2.5.0/gems/rack-2.0.7/lib/rack/session/pool.rb:6:in <top (required)>'
Nov 08 15:36:57 blouinfe ruby[5069]: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in require’ Nov 08 15:36:57 blouinfe ruby[5069]: from /usr/lib/one/sunstone/sunstone-server.rb:94:in <main>'
Nov 08 15:36:57 blouinfe systemd[1]: opennebula-sunstone.service: Main process exited, code=exited, status=1/FAILURE
Nov 08 15:36:58 blouinfe systemd[1]: opennebula-sunstone.service: Failed with result 'exit-code'.