1 __ 2 (___()'`; Rusty's Remarkably Unreliable Guide to Lguest 3 /, /` - or, A Young Coder's Illustrated Hypervisor 4 \\"--\\ http://lguest.ozlabs.org 5 6Lguest is designed to be a minimal hypervisor for the Linux kernel, for 7Linux developers and users to experiment with virtualization with the 8minimum of complexity. Nonetheless, it should have sufficient 9features to make it useful for specific tasks, and, of course, you are 10encouraged to fork and enhance it (see drivers/lguest/README). 11 12Features: 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 19Developer 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 25Running 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 117There is a helpful mailing list at http://ozlabs.org/mailman/listinfo/lguest 118 119Good luck! 120Rusty Russell rusty@rustcorp.com.au. 121