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<h1>Qemu</h1>
<h2 id="kern">1. Host System</h2>
<p>Prepare host system for virtual machines, this includes create new user,
loading necessary modules and configure network. Load kvm module, in this example
intel module is loaded but depends on host cpu;</p>
<pre>
# modprobe -a kvm-intel tun virtio
</pre>
<p>Add users to kvm group;</p>
<pre>
# usermod -a -G kvm c9admin
# usermod -a -G kvm username
</pre>
<h2 id="disk">2. Disk images</h2>
<p>Qemu supports multiple disk images types.</p>
<dl>
<dt>img</dt>
<dd>Raw disk image, allows dd to a physical device.</dd>
<dt>raw</dt>
<dd>Raw disk image, allows dd to a physical device.</dd>
<dt>qcow2</dt>
<dd>Qcow disk image file used by qemu.</dd>
</dl>
<p>Create hard disk image, there is different types,
this describes how to create a qcow2 type;</p>
<pre>
$ qemu-img create -f qcow2 crux-img.qcow2 15G
</pre>
<p>You can mount disk image;</p>
<pre>
$ sudo modprobe nbd
$ sudo qemu-nbd -c /dev/nbd0 /crux-img.qcow2
</pre>
<p>To disconnect image disk (ndb);</p>
<pre>
$ sudo qemu-nbd -d /dev/nbd0
</pre>
<p>Information about preparing
<a href="../core/install.html#step2">partitions</a>
and <a href="storage.html">storage</a> administration.
You can use image as a normal disk, example how
to use parted to create a gpt system table;</p>
<pre>
# parted --script $DEV \
mklabel gpt \
mkpart ESP fat32 1MiB 120MiB \
mkpart primary ext4 120MiB 720MiB \
mkpart primary ext4 720MiB 2720MiB \
mkpart primary ext4 2720MiB 5000MiB \
set 1 boot on
</pre>
<pre>
# kpartx -a -s -l -u /dev/nbd0
</pre>
<p>Use /dev/mapper/$(name_of_device) to assign correct blocks;</p>
<pre>
# mkfs.fat -F 32 $BLK_EFI
# mkfs.ext4 $BLK_BOOT
# mkfs.ext4 $BLK_ROOT
# mkfs.ext4 $BLK_VAR
</pre>
<p>Mount partition;</p>
<pre>
# mount $BLK_ROOT $CHROOT
# mkdir -p $CHROOT/boot
# mount $BLK_BOOT $CHROOT/boot
# mkdir -p $CHROOT/boot/efi
# mount $BLK_EFI $CHROOT/boot/efi
# mkdir -p $CHROOT/var
# mount $BLK_VAR $CHROOT/var
</pre>
<h2 id="net">2. Network</h2>
<p>Network configuration;</p>
<dl>
<dt>slirp</dt>
<dd>Default virtual NAT'd network.</dd>
<dt>tun/tap</dt>
<dd>Good performance to create virtually any type of network
topology.</dd>
<dt>vde</dt>
<dd>The VDE networking backend.</dd>
</dl>
<pre>
KERNEL=="tun", GROUP="kvm", MODE="0660", OPTIONS+="static_node=net/tun"
</pre>
<h3>2.1. Routing</h3>
<p>Create interface with correct permissions set for kvm group.</p>
<pre>
# sysctl -w net.ipv4.ip_forward=1
# iptables -A INPUT -i br0 -j ACCEPT
# iptables -A FORWARD -i br0 -j ACCEPT
# iptables -t nat -A POSTROUTING -s 10.0.0.0/24 -d 10.0.0.0/24 -j ACCEPT
# iptables -t nat -A POSTROUTING -s 10.0.0.0/24 -j MASQUERADE
</pre>
<h3>2.2. Public Bridge</h3>
<p>Create <a href="network.html#bridge">bridge</a>, create new
tap and add it to bridge;</p>
<pre>
DEV="br0"
ADDR=10.0.0.254
NET=10.0.0.0
GW=192.168.1.254
MASK=24
# one tap for each cpu core
NTAPS=$((`/usr/bin/nproc`))
case $1 in
start)
/sbin/ip link add name ${DEV} type bridge
/sbin/ip addr add ${ADDR}/${MASK} dev ${DEV} broadcast +
/sbin/ip link set dev ${DEV} up
/bin/sleep 0.2s
for i in `/usr/bin/seq $NTAPS`
do
TAP="tap$i"
echo "Setting up ${TAP} tap interface."
/sbin/ip tuntap add ${TAP} mode tap group kvm
/sbin/ip link set ${TAP} up
/bin/sleep 0.2s
/sbin/ip link set ${TAP} master ${DEV}
done
exit 0
;;
stop)
for i in `/usr/bin/seq $NTAPS`
do
TAP="tap$i"
echo "Deleting ${TAP} tap interface."
/sbin/ip link del ${TAP}
done
/sbin/ip link set dev ${DEV} down
/sbin/ip route flush dev ${DEV}
/sbin/ip link del ${DEV}
exit 0
;;
restart)
$0 stop
$0 start
;;
*)
echo "Usage: $0 [start|stop|restart]"
;;
esac
# End of file
</pre>
<h2 id="guest">Guest System</h2>
<p>See <a href="scripts/runvm/runvm.sh">scripts/runvm/runvm.sh</a>,
as template. Example scripts;</p>
<p>runvm/profile/crux</p>
<pre>
iso=iso/crux-3.2.iso
image=img/crux-img.qcow2
tap="tap1"
</pre>
<p>runvm/runvm.sh</p>
<pre>
#!/bin/bash
function rmac_addr (){
printf '54:60:BE:EF:%02X:%02X\n' $((RANDOM%256)) $((RANDOM%256))
}
source profile/$1
boot=$2
mac=$(rmac_addr)
qemu-system-x86_64 \
-enable-kvm \
-m 1024 \
-boot ${boot} \
-cdrom ${iso} \
-hda ${image} \
-vga std \
-display sdl \
-device e1000,netdev=t0,mac=${mac} \
-netdev tap,id=t0,ifname=${tap},script=no,downscript=no \
&
</pre>
<p>Set guests machines to run under the total resolution provided
by host system configure grub on the guest with gfxmode;</p>
<pre>
GRUB_GFXMODE=640x480
GRUB_GFXPAYLOAD_LINUX=keep
</pre>
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<p>This is part of the c9 Manual.
Copyright (C) 2016
c9 team.
See the file <a href="../fdl-1.3-standalone.html">Gnu Free Documentation License</a>
for copying conditions.</p>
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