130 lines
4.4 KiB
Plaintext
130 lines
4.4 KiB
Plaintext
__
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(___()'`; Rusty's Remarkably Unreliable Guide to Lguest
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/, /` - or, A Young Coder's Illustrated Hypervisor
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\\"--\\ http://lguest.ozlabs.org
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Lguest is designed to be a minimal 32-bit x86 hypervisor for the Linux kernel,
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for Linux developers and users to experiment with virtualization with the
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minimum of complexity. Nonetheless, it should have sufficient features to
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make it useful for specific tasks, and, of course, you are encouraged to fork
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and enhance it (see drivers/lguest/README).
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Features:
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- Kernel module which runs in a normal kernel.
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- Simple I/O model for communication.
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- Simple program to create new guests.
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- Logo contains cute puppies: http://lguest.ozlabs.org
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Developer features:
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- Fun to hack on.
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- No ABI: being tied to a specific kernel anyway, you can change anything.
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- Many opportunities for improvement or feature implementation.
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Running Lguest:
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- The easiest way to run lguest is to use same kernel as guest and host.
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You can configure them differently, but usually it's easiest not to.
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You will need to configure your kernel with the following options:
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"General setup":
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"Prompt for development and/or incomplete code/drivers" = Y
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(CONFIG_EXPERIMENTAL=y)
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"Processor type and features":
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"Paravirtualized guest support" = Y
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"Lguest guest support" = Y
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"High Memory Support" = off/4GB
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"Alignment value to which kernel should be aligned" = 0x100000
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(CONFIG_PARAVIRT=y, CONFIG_LGUEST_GUEST=y, CONFIG_HIGHMEM64G=n and
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CONFIG_PHYSICAL_ALIGN=0x100000)
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"Device Drivers":
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"Block devices"
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"Virtio block driver (EXPERIMENTAL)" = M/Y
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"Network device support"
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"Universal TUN/TAP device driver support" = M/Y
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"Virtio network driver (EXPERIMENTAL)" = M/Y
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(CONFIG_VIRTIO_BLK=m, CONFIG_VIRTIO_NET=m and CONFIG_TUN=m)
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"Virtualization"
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"Linux hypervisor example code" = M/Y
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(CONFIG_LGUEST=m)
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- A tool called "lguest" is available in this directory: type "make"
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to build it. If you didn't build your kernel in-tree, use "make
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O=<builddir>".
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- Create or find a root disk image. There are several useful ones
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around, such as the xm-test tiny root image at
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http://xm-test.xensource.com/ramdisks/initrd-1.1-i386.img
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For more serious work, I usually use a distribution ISO image and
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install it under qemu, then make multiple copies:
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dd if=/dev/zero of=rootfile bs=1M count=2048
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qemu -cdrom image.iso -hda rootfile -net user -net nic -boot d
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Make sure that you install a getty on /dev/hvc0 if you want to log in on the
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console!
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- "modprobe lg" if you built it as a module.
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- Run an lguest as root:
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Documentation/virtual/lguest/lguest 64 vmlinux --tunnet=192.168.19.1 \
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--block=rootfile root=/dev/vda
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Explanation:
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64: the amount of memory to use, in MB.
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vmlinux: the kernel image found in the top of your build directory. You
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can also use a standard bzImage.
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--tunnet=192.168.19.1: configures a "tap" device for networking with this
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IP address.
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--block=rootfile: a file or block device which becomes /dev/vda
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inside the guest.
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root=/dev/vda: this (and anything else on the command line) are
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kernel boot parameters.
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- Configuring networking. I usually have the host masquerade, using
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"iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE" and "echo 1 >
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/proc/sys/net/ipv4/ip_forward". In this example, I would configure
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eth0 inside the guest at 192.168.19.2.
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Another method is to bridge the tap device to an external interface
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using --tunnet=bridge:<bridgename>, and perhaps run dhcp on the guest
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to obtain an IP address. The bridge needs to be configured first:
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this option simply adds the tap interface to it.
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A simple example on my system:
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ifconfig eth0 0.0.0.0
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brctl addbr lg0
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ifconfig lg0 up
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brctl addif lg0 eth0
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dhclient lg0
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Then use --tunnet=bridge:lg0 when launching the guest.
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See:
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http://www.linuxfoundation.org/collaborate/workgroups/networking/bridge
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for general information on how to get bridging to work.
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- Random number generation. Using the --rng option will provide a
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/dev/hwrng in the guest that will read from the host's /dev/random.
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Use this option in conjunction with rng-tools (see ../hw_random.txt)
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to provide entropy to the guest kernel's /dev/random.
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There is a helpful mailing list at http://ozlabs.org/mailman/listinfo/lguest
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Good luck!
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Rusty Russell rusty@rustcorp.com.au.
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