Update content.md

swift/content.md

@@ -18,6 +18,14 @@ The goal of the Swift project is to create the best available language for uses
 
 # How to use this image
 
+##### Start a REPL
+
+Swift requires [a little bit of extra security privilege](https://github.com/swiftdocker/docker-swift/issues/9#issuecomment-272527182) to run the REPL. The following command creates an ephemeral container, attaches your terminal to it and starts the Swift REPL. A great way to try out pre-release builds!
+
+```bash
+docker run --cap-add sys_ptrace -it --rm swiftdocker/swift swift
+```
+
 ##### Pull the Docker Image From Docker Hub:
 
 ```bash