Added SELinux section to the readme

Signed-off-by: Juanjo Alvarez <juanjo@sourced.tech>

README.md

@@ -62,6 +62,36 @@ and an example contained in the docker image:
 docker exec -it bblfshd bblfshctl parse /opt/bblfsh/etc/examples/python.py
 ```
 
+## SELinux
+
+If your system has SELinux enabled (is the default in Fedora, Red Hat, CentOS
+and many others) you need to compile and load a policy module before running the
+bblfshd Docker image or running driver containers will fail with a `permission
+denied` message in the logs. 
+
+To do this, run these commands from the project root:
+
+```bash
+cd selinux/
+sh compile.sh
+semodule -i bblfshd.pp
+```
+
+If you were already running an instance of bblfshd, you will need to delete the
+container (`docker rm -f bblfshd`) and run it again (`docker run...`).
+
+Once the module has been loaded with `semodule` the change should persist even
+if you reboot. If you want to permanently remove this module run `semodule -d bblfshd`.
+
+Alternatively, you could set SELinux to permissive module with:
+
+```
+echo 1 > /sys/fs/selinux/enforce
+```
+
+(doing this on production systems which usually have SELinux enabled by default
+should be strongly discouraged).
+
 ## Development
 
 If you wish to work on *bblfshd* , you'll first need [Go](http://www.golang.org)

runtime/runtime.go

@@ -196,8 +196,8 @@ func Bootstrap() {
 		factory, _ := libcontainer.New("")
 		if err := factory.StartInitialization(); err != nil {
 			panic("error bootstraping container " +
-			      "(hint: if SELinux is enabled, compile and load the policy module " +
-				  "in the selinux/ directory in the bblfshd repo): " + err)
+				"(hint: if SELinux is enabled, compile and load the policy module " +
+				"in this repo's selinux/ directory): " + err)
 		}
 		panic("--this line should have never been executed, congratulations--")
 	}

selinux/compile.sh

@@ -2,6 +2,4 @@
 
 checkmodule -M -m -o bblfshd.mod bblfshd.te && \
     semodule_package -o bblfshd.pp -m bblfshd.mod && \
-    echo 'Module compiled, load it with semodule -i bblfshd.pp'
-
-# enable with: semodule -i bblfshd.pp
+    echo 'Module compiled, load it with "semodule -i bblfshd.pp"'