Do you know how to modify the value of “max open files” for a running process? You can modify that it is using the command “prlimit”(You can also modify more than just “max open files”). docker-prlimit-example makes it easy to try. Run the following commands in order to connect to the docker container where the unicorn process is running. $ git clone $ cd docker-prlimit-example $ docker build -t prlimit .