Server is already running in Rails

kill -9 $(lsof -i tcp:3000 -t)

Remove the file: C:/Sites/folder/Pids/Server.pids

Explanation In UNIX land at least we usually track the process id (pid) in a file like server.pid. I think this is doing the same thing here. That file was probably left over from a crash.

TL;DR Just Run this command to Kill it

sudo kill -9 $(lsof -i :3000 -t)

Root Cause: Because PID is locked in a file and web server thinks that if that file exists then it means it is already running. Normally when a web server is closed that file is deleted, but in some cases, proper deletion doesn't happen so you have to remove the file manually New Solutions

when you run rails s

=> Booting WEBrick

=> Rails 4.0.4 application starting in development on http://0.0.0.0:3000

=> Run rails server -h for more startup options

=> Ctrl-C to shutdown server

A server is already running. Check /your_project_path/tmp/pids/server.pid. Exiting

So place your path shown here /your_project_path/tmp/pids/server.pid

and remove this server.pid file:

rm /your_project_path/tmp/pids/server.pid

OR Incase you're server was detached then follow below guidelines:

If you detached you rails server by using command "rails -d" then,

Remove rails detached server by using command

ps -aef | grep rails

OR by this command

sudo lsof -wni tcp:3000

then

kill -9 pID

OR use this command

To find and kill process by port name on which that program is running. For 3000 replace port on which your program is running.

sudo kill -9 $(lsof -i :3000 -t)

Old Solution:

rails s -p 4000 -P tmp/pids/server2.pid

Also you can find this post for more options Rails Update to 3.2.11 breaks running multiple servers

lsof -wni tcp:3000

Then you should see the ruby process and you can run

kill -9 processid

you should be good to run the process now

rails s thin

running multiple processes doesn't seem like a good idea and from what i've read many people agree. I've noticed many memory leaks with rails unfortunately so I couldn't imagine having two processes running. I know with one overtime my page refreshes increasingly become slower because of the data being stored on memory.