CS3 Operating Systems 2013-14, Practical Exercise.

PHASE 1
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Running a virtual Linux system
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For rather obvious reasons, we can't let you loose in the kernel of one
of our machines. However, nowadays there are available excellent
emulators which allow you to run an entire modern system inside an
emulated PC - and modern PCs are so fast that this emulation is itself
capable of running applications (never mind OS exercises) at a
perfectly reasonable speed. Therefore you will do your kernel
programming inside such a virtual machine.

The emulator we'll use is Oracle's VirtualBox. You *could* run it at
home, but on the whole I recommend doing the practical on DICE.


Running VirtualBox on DICE machines
-----------------------------------

NOTE: these instructions work ONLY on DICE machines, and moreover you
must have an X display set. That is, you must either be on a DICE
workstation, or you must be logged from via ssh with X display
forwarding enabled. (Or you must have explicitly set an appropriate
DISPLAY.) Do NOT run VirtualBox on any of the School's server
machines.

A former Teaching Assistant Zheng Wang has made it very easy for
you to set up VirtualBox for this practical. Here is what to do:

Bring up an xterm (or whatever other shell window you use -- doing
this inside an Emacs shell buffer is possible, but advisable only for
hardcore Emacsers).
Make a directory for this practical, and cd into it.

Then issue the command:

/group/teaching/cs3/os/VBox/setup.sh

and follow the instructions it gives you.

After this, you will be able to start your virtual machine just by
starting VirtualBox .

When you start VirtualBox, the application GUI will appear; when you
start the virtual machine just created, a console window (which is the
console tty of the VM) will appear. You will see a normal Linux boot
sequence, and then you should see a login prompt.

Now log in (as "root" if you're feeling confident, or "user" if
you're feeling nervous) and have a look round the virtual machine.

Shutting down: to shutdown your virtual machine, log in to the console
as root, and do
shutdown -h now
Note that an unclean shutdown will have the same mangling effect on
your virtual disk that an unclean shutdown of a real machine has on
its real disks, so you should always follow this procedure.

The VM has two virtual disks attached. One is mounted on /, and
contains the system - it is a stripped down Fedora system. NOTE that
you cannot make any permanent changes to files - any changes you make
will be lost when you shut down the VM. To provide VM-internal
storage, a second disk is mounted on /work, and changes in here are
persistent. Note that this second virtual disk is in reality a file in
your filespace, so consumes part of your quota - so don't copy any BIG
files into /work .

When the VM was set up for you, a directory called "shared" was
created in your practical directory. You can mount this in the VM by
(as root):
 mount -t vboxsf shared /mnt/shared

Finally, you may (indeed, will!) get to a state where your console is
wedged with a command not responding. It is not possible (currently)
to ssh in to your VM from outside; however, like all standard Linux
systems, the system has six virtual (i.e. virtually virtual!) consoles
available on the (virtually real) system console. You can switch to
virtual console N by pressing Host-FnN, where Host is the right
Control key (unless you've changed it). So to switch to virtual
console 2, press Host-Fn2. You can then log in there.