Oops: "pids" -> "numeric userid" (#98)

"pids" is process ids, I think?

What you mean is the users numeric id, e.g. on machine A `hartzell` is `3245` so files are owned by `3245`.  But, when I get to machine B where `hartzell` is `22453`, those same files appear to be someone else.

Right?

Author: hartzell

pages/docs/user-docs/docs-changing-containers.md

@@ -7,7 +7,7 @@ folder: docs
 
 
 # Making Changes to an Existing Container
-It is possible that you may need to make changes to a container after it has been bootstrapped. For that, let's repeat the Singularity mantra "*A user inside a Singularity container is the same user as outside the container*". If you want to make changes to your container, you must mount the container as `--writable` so you can change the contents. Note that standard Linux ownership and permission rules pertain to files within the container, so the `--writable` option does not guarantee you can do things like install new software. This might be a bit confusing if you copy a container from one computer to another. If your pids are different on the two computers you will lose the ability to edit files you previous had write access to. In these instances, it might be best to modify your container as root and so you would first need to become root outside of the container. Let's examine the following example:
+It is possible that you may need to make changes to a container after it has been bootstrapped. For that, let's repeat the Singularity mantra "*A user inside a Singularity container is the same user as outside the container*". If you want to make changes to your container, you must mount the container as `--writable` so you can change the contents. Note that standard Linux ownership and permission rules pertain to files within the container, so the `--writable` option does not guarantee you can do things like install new software. This might be a bit confusing if you copy a container from one computer to another. If your numeric userid are different on the two computers you will lose the ability to edit files you previous had write access to. In these instances, it might be best to modify your container as root and so you would first need to become root outside of the container. Let's examine the following example:
 
 ## Installing Additional Software
 We strongly recommend that you add additional software installation to your bootstrap, and re-create the image. However if you must, you can use `shell` and `exec` with `--writable` to issue additional commands.