Improve nsinit usage instructions

nsinit must be run as root.

Tidy up the README somewhat to clarify the distinction between
libcontainer and the nsinit CLI.

Fix some typos in other files.

Docker-DCO-1.1-Signed-off-by: Glyn Normington <gnormington@gopivotal.com> (github: glyn)

README.md

@@ -6,37 +6,43 @@ Please bear with us while we work on making the libcontainer API stable and some
 
 #### Background
 
-libcontainer specifies configuration options for what a container is.  It provides a native Go implementation 
-for using Linux namespaces with no external dependencies.  libcontainer provides many convenience functions for working with namespaces, networking, and management.  
+libcontainer specifies configuration options for what a container is.  It provides a native Go implementation for using Linux namespaces with no external dependencies.  libcontainer provides many convenience functions for working with namespaces, networking, and management.  
 
 
 #### Container
-A container is a self contained directory that is able to run one or more processes without 
-affecting the host system.  The directory is usually a full system tree.  Inside the directory
-a `container.json` file is placed with the runtime configuration for how the processes 
-should be contained and run.  Environment, networking, and different capabilities for the 
-process are specified in this file.  The configuration is used for each process executed inside the container.
+A container is a self contained execution environment that shares the kernel of the host system and which is (optionally) isolated from other containers in the system.
 
-See the `sample_configs` folder for examples of what the container configuration should look like.
+libcontainer may be used to execute a process in a container. If a user tries to run a new process inside an existing container, the new process is added to the processes executing in the container.
 
-Using this configuration and the current directory holding the rootfs for a process, one can use libcontainer to exec the container. During the life of the container, a `state.json` file 
-is written to the current directory with the pid and start time of the container's PID1.  A client can use this pid to wait, kill, or perform other operation with the container.  If a user tries to run a new process inside an existing container with a live namespace, the namespace will be joined by the new process.
 
-You may also specify an alternate root place where the `container.json` file is read and where the `state.json` file will be saved.
+#### Root file system
+
+A container runs with a directory known as its *root file system*, or *rootfs*, mounted as the file system root. The rootfs is usually a full system tree.
+
+
+#### Configuration
+
+A container is initially configured by supplying configuration data when the container is created.
+
 
 #### nsinit
 
-`nsinit` is a cli application used as the reference implementation of libcontainer.  It is able to 
-spawn or join new containers giving the current directory.  To use `nsinit` cd into a Linux 
-rootfs and copy a `container.json` file into the directory with your specified configuration.
+`nsinit` is a cli application which demonstrates the use of libcontainer.  It is able to spawn new containers or join existing containers, based on the current directory.
 
-To execute `/bin/bash` in the current directory as a container just run:
+To use `nsinit`, cd into a Linux rootfs and copy a `container.json` file into the directory with your specified configuration. Environment, networking, and different capabilities for the container are specified in this file. The configuration is used for each process executed inside the container.
+                                                                                                                               
+See the `sample_configs` folder for examples of what the container configuration should look like.
+
+To execute `/bin/bash` in the current directory as a container just run the following **as root**:
 ```bash
 nsinit exec /bin/bash
 ```
 
-If you wish to spawn another process inside the container while your current bash session is 
-running just run the exact same command again to get another bash shell or change the command.  If the original process dies, PID 1, all other processes spawned inside the container will also be killed and the namespace will be removed. 
+If you wish to spawn another process inside the container while your current bash session is running, run the same command again to get another bash shell (or change the command).  If the original process (PID 1) dies, all other processes spawned inside the container will be killed and the namespace will be removed. 
+
+You can identify if a process is running in a container by looking to see if `state.json` is in the root of the directory.
+   
+You may also specify an alternate root place where the `container.json` file is read and where the `state.json` file will be saved.
 
 #### Future
 See the [roadmap](ROADMAP.md).

mount/init.go

@@ -25,8 +25,8 @@ type mount struct {
 	data   string
 }
 
-// InitializeMountNamespace setups up the devices, mount points, and filesystems for use inside a
-// new mount namepsace
+// InitializeMountNamespace sets up the devices, mount points, and filesystems for use inside a
+// new mount namespace.
 func InitializeMountNamespace(rootfs, console string, mountConfig *MountConfig) error {
 	var (
 		err  error

namespaces/exec.go

@@ -17,7 +17,7 @@ import (
 
 // TODO(vishh): This is part of the libcontainer API and it does much more than just namespaces related work.
 // Move this to libcontainer package.
-// Exec performes setup outside of a namespace so that a container can be
+// Exec performs setup outside of a namespace so that a container can be
 // executed.  Exec is a high level function for working with container namespaces.
 func Exec(container *libcontainer.Config, term Terminal, rootfs, dataPath string, args []string, createCommand CreateCommand, startCallback func()) (int, error) {
 	var (
@@ -107,10 +107,10 @@ func Exec(container *libcontainer.Config, term Terminal, rootfs, dataPath string
 // args provided
 //
 // console: the /dev/console to setup inside the container
-// init: the progam executed inside the namespaces
+// init: the program executed inside the namespaces
 // root: the path to the container json file and information
-// pipe: sync pipe to syncronize the parent and child processes
-// args: the arguemnts to pass to the container to run as the user's program
+// pipe: sync pipe to synchronize the parent and child processes
+// args: the arguments to pass to the container to run as the user's program
 func DefaultCreateCommand(container *libcontainer.Config, console, rootfs, dataPath, init string, pipe *os.File, args []string) *exec.Cmd {
 	// get our binary name from arg0 so we can always reexec ourself
 	env := []string{
@@ -141,7 +141,7 @@ func DefaultCreateCommand(container *libcontainer.Config, console, rootfs, dataP
 	return command
 }
 
-// SetupCgroups applies the cgroup restrictions to the process running in the contaienr based
+// SetupCgroups applies the cgroup restrictions to the process running in the container based
 // on the container's configuration
 func SetupCgroups(container *libcontainer.Config, nspid int) (cgroups.ActiveCgroup, error) {
 	if container.Cgroups != nil {