Documentation/lguest/lguest.txt

   1       __
   2  (___()'`;  Rusty's Remarkably Unreliable Guide to Lguest
   3  /,    /`      - or, A Young Coder's Illustrated Hypervisor
   4  \\"--\\    http://lguest.ozlabs.org
   5
   6 Lguest is designed to be a minimal hypervisor for the Linux kernel, for
   7 Linux developers and users to experiment with virtualization with the
   8 minimum of complexity.  Nonetheless, it should have sufficient
   9 features to make it useful for specific tasks, and, of course, you are
  10 encouraged to fork and enhance it (see drivers/lguest/README).
  11
  12 Features:
  13
  14 - Kernel module which runs in a normal kernel.
  15 - Simple I/O model for communication.
  16 - Simple program to create new guests.
  17 - Logo contains cute puppies: http://lguest.ozlabs.org
  18
  19 Developer features:
  20
  21 - Fun to hack on.
  22 - No ABI: being tied to a specific kernel anyway, you can change anything.
  23 - Many opportunities for improvement or feature implementation.
  24
  25 Running Lguest:
  26
  27 - The easiest way to run lguest is to use same kernel as guest and host.
  28   You can configure them differently, but usually it's easiest not to.
  29
  30   You will need to configure your kernel with the following options:
  31
  32   "General setup":
  33      "Prompt for development and/or incomplete code/drivers" = Y
  34         (CONFIG_EXPERIMENTAL=y)
  35
  36   "Processor type and features":
  37      "Paravirtualized guest support" = Y
  38         "Lguest guest support" = Y
  39      "High Memory Support" = off/4GB
  40      "Alignment value to which kernel should be aligned" = 0x100000
  41         (CONFIG_PARAVIRT=y, CONFIG_LGUEST_GUEST=y, CONFIG_HIGHMEM64G=n and
  42          CONFIG_PHYSICAL_ALIGN=0x100000)
  43
  44   "Device Drivers":
  45      "Block devices"
  46         "Virtio block driver (EXPERIMENTAL)" = M/Y
  47      "Network device support"
  48         "Universal TUN/TAP device driver support" = M/Y
  49         "Virtio network driver (EXPERIMENTAL)" = M/Y
  50            (CONFIG_VIRTIO_BLK=m, CONFIG_VIRTIO_NET=m and CONFIG_TUN=m)
  51
  52   "Virtualization"
  53      "Linux hypervisor example code" = M/Y
  54         (CONFIG_LGUEST=m)
  55
  56 - A tool called "lguest" is available in this directory: type "make"
  57   to build it.  If you didn't build your kernel in-tree, use "make
  58   O=<builddir>".
  59
  60 - Create or find a root disk image.  There are several useful ones
  61   around, such as the xm-test tiny root image at
  62           http://xm-test.xensource.com/ramdisks/initrd-1.1-i386.img
  63
  64   For more serious work, I usually use a distribution ISO image and
  65   install it under qemu, then make multiple copies:
  66
  67           dd if=/dev/zero of=rootfile bs=1M count=2048
  68           qemu -cdrom image.iso -hda rootfile -net user -net nic -boot d
  69
  70   Make sure that you install a getty on /dev/hvc0 if you want to log in on the
  71   console!
  72
  73 - "modprobe lg" if you built it as a module.
  74
  75 - Run an lguest as root:
  76
  77       Documentation/lguest/lguest 64 vmlinux --tunnet=192.168.19.1 --block=rootfile root=/dev/vda
  78
  79    Explanation:
  80     64: the amount of memory to use, in MB.
  81
  82     vmlinux: the kernel image found in the top of your build directory.  You
  83        can also use a standard bzImage.
  84
  85     --tunnet=192.168.19.1: configures a "tap" device for networking with this
  86        IP address.
  87
  88     --block=rootfile: a file or block device which becomes /dev/vda
  89        inside the guest.
  90
  91     root=/dev/vda: this (and anything else on the command line) are
  92        kernel boot parameters.
  93
  94 - Configuring networking.  I usually have the host masquerade, using
  95   "iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE" and "echo 1 >
  96   /proc/sys/net/ipv4/ip_forward".  In this example, I would configure
  97   eth0 inside the guest at 192.168.19.2.
  98
  99   Another method is to bridge the tap device to an external interface
 100   using --tunnet=bridge:<bridgename>, and perhaps run dhcp on the guest
 101   to obtain an IP address.  The bridge needs to be configured first:
 102   this option simply adds the tap interface to it.
 103
 104   A simple example on my system:
 105
 106     ifconfig eth0 0.0.0.0
 107     brctl addbr lg0
 108     ifconfig lg0 up
 109     brctl addif lg0 eth0
 110     dhclient lg0
 111
 112   Then use --tunnet=bridge:lg0 when launching the guest.
 113
 114   See http://linux-net.osdl.org/index.php/Bridge for general information
 115   on how to get bridging working.
 116
 117 There is a helpful mailing list at http://ozlabs.org/mailman/listinfo/lguest
 118
 119 Good luck!
 120 Rusty Russell rusty@rustcorp.com.au.