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Based on kernel version 2.6.39.1. Page generated on 2011-06-03 13:47 EST.

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 32-bit x86 hypervisor for the Linux kernel,
7	for Linux developers and users to experiment with virtualization with the
8	minimum of complexity.  Nonetheless, it should have sufficient features to
9	make it useful for specific tasks, and, of course, you are encouraged to fork
10	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:
115	  
116	    http://www.linuxfoundation.org/collaborate/workgroups/networking/bridge
117	    
118	  for general information on how to get bridging to work.
119	
120	- Random number generation. Using the --rng option will provide a
121	  /dev/hwrng in the guest that will read from the host's /dev/random.
122	  Use this option in conjunction with rng-tools (see ../hw_random.txt)
123	  to provide entropy to the guest kernel's /dev/random.
124	
125	There is a helpful mailing list at http://ozlabs.org/mailman/listinfo/lguest
126	
127	Good luck!
128	Rusty Russell rusty@rustcorp.com.au.
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