Listen error: unable to monitor directories for changes

I am getting the following error while running my rails app in Ubuntu server > FATAL: Listen error: unable to monitor directories for changes. Visit > https://github.com/guard/listen/wiki/Increasing-the-amount-of-inotify-watchers > for info on how to fix this. I have followed the above GitHub page, but I was unable to write in max_user_watches which were set in 8192 and I want to set that to 524288. in `cat /proc/sys/fs/inotify/max_user_watches` the file was in only read mode.I tried to grant write permissions, but I was getting permission denied error even with root access. Thanks in Advance!!!