virt_install_notes.txt

Assuming that kvm and libvirt have never been used on your system
previously, the following should set up the necessary environment::

  # Install kvm, libvirt, and virt-install
  sudo apt-get update
  sudo apt-get install -y kvm libvirt-bin virtinst

  # Enable the default network bridge (needed for SSH access)
  sudo virsh net-autostart default
  sudo virsh net-start default

Disk images are stored in /var/lib/libvirt/images by default.  If this
is not okay, then replace this folder with an appropriate symlink.
(Alternatively, you probably can dump the XML of the disk pool, put in
a different directory and then re-create the pool.)

To create a VM compatible with the scripts in this repository, use
virt-install with options similar to those which follow.  Update it as
you like, but please note these requirements:

- The CD image is assumed to be Ubuntu 10.10 Desktop i386.  Other host
  environments have not been tested.

- It is assumed that the VM has a single 20 GB disk, so it's generally
  advised to leave the "--disk" flag as-is.

- I suggest using the "format=qcow2" option on the disk as specified
  below.  This allows for the use of disk overlays which, although an
  advanced virtualization feature, allows for a form of disk snapshots
  which additional VMs can be based off of.  (Some people may call
  these images "templates").

The command is as follows::

  sudo virt-install \
    --name lfs1 \
    --ram 4096 \
    --disk pool=default,format=qcow2,size=20 \
    --cdrom=/home/vultaire/ubuntu-10.10-desktop-i386.iso

Wait for the VM viewer window to pop up, and select to "Try Ubuntu".
Once the regular desktop appears, from the viewer window's menu,
select "Send key", then "Ctrl + Alt + F1".  This will get to a
console.

If running on a non-US keyboard, it's helpful to load the appropriate
keymap.  I don't know all codes, but for my keyboard, the following
works::

  sudo loadkeys jp

The password for the ubuntu user should be changed, so::

  sudo passwd ubuntu  # "sudo" will skip some password safety checks.
  # Enter a password.  We'll use this later.

Next, install SSH::

  sudo apt-get install -y openssh-server

Finally, let's set up DNS for this VM::

  sudo hostname <vm_name>
  sudo dhclient eth0  # Refreshes DNS

From here, SSH access should work.  To get the IP address, you can use
a line as follows::

  # -From outside of the VM-
  function vm_host () {
      vm_name="$1"
      host -t A "$vm_name" 192.168.122.1 \
          | grep "^$vm_name has address" \
          | awk '{print $4}'
  }
  vm_addr=$(vm_host "<vm_name>")  # vm_addr will receive the IP address.

I assume you already have a working SSH key; if not, run ssh-keygen to
create one.

It's probably convenient to copy your key to the VM; this can be done
with "ssh-copy-id ubuntu@<vm_ip>".

Now, you are ready to create an LFS system via an SSH shell in a VM.
You can close the VM's viewer window; the VM will still be running in
the background.

You're ready to begin, but a few VM control notes:

1. VM commands should always be run via sudo. `1`_

2. To save a VM's state to disk (stops the VM)::

     sudo virsh save <vm_name> <path/to/target.file>

3. To restore a VM from a saved state file (starts the VM
   automatically)::

     sudo virsh restore <path/to/target.file>

4. To shutdown a VM gracefully::

     sudo virsh shutdown <vm_name>

   Note that the VM must have ACPI support installed.  The Ubuntu
   10.10 environment does have acpid installed, so it should work
   without modification.

5. To destroy a VM completely::

     sudo virsh destroy <vm_name>   # Terminates the VM (if running)
     sudo virsh undefine <vm_name>  # Deletes the VM definition from libvirt.
     sudo virsh vol-delete --pool default <disk_img_name_or_path> `2`_

A final note: some versions of libvirt and kvm seem to have issues
with save and restore.  On my host machine, intermittently this does
not work: the commands run, but the resulting restored VM is
unusable. `3`_ The simplest way to avoid this is to not stop until the
VM is self-bootable.  Alternatively, the boot CD could be re-mounted
and the needed prerequisites re-installed; if you go this route,
you're on your own.

.. [1] Well, not really.  Of course, you should avoid using root or
   sudo unless you need to.  However, libvirt controls virtual network
   devices and disk pools, and these may not show up unless the root
   account is used.  Sorry, but I don't yet know the appropriate group
   permissions so that virsh and virt-install work in their entirety
   without problems... so for now, "sudo" it is.

.. [2] Usually, the disk image's name is "<vm_name>.img".

.. [3] Debian Squeeze, libvirt0==0.8.3-5+squeeze1,
   kvm==1:0.12.5+dfsg-5+squeeze2.