Okay so you've finished the 12-step programme and you're wondering what the

heck you just did.

1. Put a translator on /tmp/hello

# settrans -a /tmp/hello /hurd/hello --contents="hello hurd

> "

You can use settrans to make a program provide the contents of a file.

You started a program (/hurd/hello) and placed it on a node on the

filesystem (/tmp/hello). You specified a --contents option to the translator.

2. Try out the new translator

# cat /tmp/hello

The usual programs trigger the program in the usual expected ways.

You triggered the running hello translator that sits on /tmp/hello to

provide it's contents.

3. See the subhurd boot script

# cat /boot/subhurd.script

Subhurds require a funny-looking script to work.

4. Start a subhurd

# boot -D /tmp -I /boot/subhurd.script -Tdevice hd2

You can start your own subhurd complete with your own filesystem.

This is running a kernel within a kernel, on top of one microkernel.

5. See the pretty pr0cesses

# ps -ef

Some processes in a subhurd don't show up correctly. For kicks you can

ask a Hurd expert about why this is the case.

6. Check to see if the hello translator is providing /tmp/hello

# cat /tmp/hello

Here you see that the hello translator applies to the parent hurd, and

not the subhurd. The hello translator simply isn't running in this subhurd.

/tmp/hello in the subhurd and /tmp/hello in the parent hurd are *not* the same

file. The subhurd takes the CD as a filesystem, and so does parent subhurd.

7. Put a translator on /tmp/hello

# settrans -a /tmp/hello /hurd/hello --contents="hello subhurd"

8. Try out the new translator

# cat /tmp/hello

9. Change the translator's settings

# fsysopts /tmp/hello --contents="hello subhurd

> "

Here you see that you can use fsysopts to send options to a running translator.

Amazing. We didn't start a new translator here, we passed a message to the

running translator about how to change it's operation.

10. Try out the revised translator

# cat /tmp/hello

11. Exit the subhurd

# halt

Here you learn how to get out of a subhurd.

Isn't it nifty how it cleans us after itself? Sure it is.

12. Check to see what /tmp/hello says

# cat /tmp/hello

You've done all of this as root, but guess what -- you can do all of this as

a regular user on a full-fledged hurd system.