Running gPXE within qemu
========================

Michael Brown <mbrown@fensystems.co.uk>

To get qemu running is fairly simple:

1.  Build the utilities in this directory:
      make

2.  Get the qemu source code:
      svn co svn://svn.savannah.nongnu.org/qemu/trunk qemu

2a. Patch the qemu code.  There is currently a bug that causes qemu to
    execute gPXE incredibly slowly.  The bug seems to be related
    to the relative prioritisation of CPU and I/O operations within
    qemu.  This patch (which I found via Google) isn't a proper fix,
    but it does work around the problem:
      patch -p0 < qemu-patch

3.  Configure qemu with
      pushd qemu
      ./configure --target-list=i386-softmmu,x86_64-softmmu
      popd

4.  Build qemu:
      make -C qemu

5.  As root, set up a TAP virtual network device:
      /sbin/modprobe tun
      chmod o+rw /dev/net/tun
      ./tunctl -u <username> -t tap0
      /sbin/ifconfig tap0 up 10.254.254.2 netmask 255.255.255.0

6.  As root, add the following fragment to /etc/dhcpd.conf:
      subnet 10.254.254.0 netmask 255.255.255.252 {
        range dynamic-bootp 10.254.254.1 10.254.254.1;
      }
    You will also need to add in any of your usual declarations for
    gPXE, e.g. 'filename "vmlinuz.ltsp";'.  Note that this setup
    assumes that your DHCP server, TFTP server etc. all live on the
    machine you are using for running qemu.  If not, then you're on
    your own.

7.  As root, restart dhcpd
      /etc/init.d/dhcpd restart

8.  Build gPXE floppy disk images and pad to 1.44MB
      pushd ../../src
      make bin/rtl8139.pdsk
      popd

9.  Start qemu
      ./qemu/i386-softmmu/qemu -L qemu/pc-bios \
			       -net nic,model=rtl8139 -net tap,ifname=tap0 \
			       -boot a -fda ../../src/bin/rtl8139.pdsk 

You should see qemu start up, load up gPXE and attempt to boot from
the network.



Serial console
==============

You can use the program "serial-console" to obtain a virtual serial
console for gPXE running within qemu.  Run "./serial-console" on a
spare tty (e.g. a separate xterm window) before starting qemu, and
ensure that you have enabled CONSOLE_SERIAL in config.h.

When serial-console starts, it will print out the message "Slave pty
is /dev/pts/XX", where XX is a number.  You need to append the option

   -serial /dev/pts/XX

to the qemu command line.

There is a manual page for "serial-console"; use "man
./serial-console.1" to view it.