README for OpenBSD users
------------------------
==> Quick Start
NOTE: amd64 cannot use '-net user' without SEGV'ing, to work around
this, either run qemu as root by replacing
qemu -m 32 ..
in this quick start section with
sudo env ETHER=em0 qemu -net nic,model=rtl8139 -net tap -m 32 ..
or by reading the 'tap mode' section below.
1. Get a bootable CDROM image
$ ftp ftp://ftp.openbsd.org/pub/OpenBSD/snapshots/i386/cd45.iso
2. Create a virtual disk image:
$ qemu-img create -f qcow2 virtual.img 10G
3. Install the os:
$ qemu -m 32 -monitor stdio -no-fd-bootchk -hda virtual.img \
-cdrom cd45.iso -boot d
NOTE: start this inside an xterm or equivalent
NOTE: be sure to choose serial console during install
NOTE: -no-fd-bootchk permits booting faster when no floppy is in use
4. Compress the virtual disk:
$ qemu-img convert -c -O qcow2 virtual.img v.tmp && mv v.tmp virtual.img
NOTE: do not do this while qemu is running / using this virtual disk
5. Boot normally from the virtual disk:
$ qemu -m 32 -nographic -no-fd-bootchk -hda virtual.img
==> Networking
1. Default Settings
By default, qemu sets up the equivalent of the following networking:
-net nic,vlan=0,model=rtl8139,macaddr=52:54:00:12:34:56
-net user,vlan=0
Also, inside this virtual usermode network, it uses the 10.0.2.0/24 and
serves dhcp from inside this virtual network. Static address can be used
if one cannot or does not want to do dhcp in the guest os:
Guest OS IP : 10.0.2.15
Default Gateway : 10.0.2.2
Nameserver : 10.0.2.3
It is sufficient for most operations, qemu itself performs NAT and then
makes userland network calls for tcp/udp operations. icmp and other things
are not possible in this mode.
NOTE: If you use one '-net' cmdline argument, qemu assumes you know what you
want and clears defaults for the rest of the -net defaults.
NOTE: The guest mode networking does not currently support IPv6, and
qemu will complain that it cannot find a dns server if
/etc/resolv.conf contains only IPv6 dns servers.
2. tap mode
Sometimes it is desirable to configure qemu to access a network via layer2
directly. One way of doing this without having to run qemu as root is to
let root open /dev/tunN and pass the file descriptor to qemu. The tun(4)
interface should preferrably be configured before starting qemu:
$ sudo ifconfig tun0 192.168.0.254 link0
The interface can also be configured as part of a bridge(4), in which case
the ip address can be omitted:
$ sudo ifconfig tun0 link0
$ sudo ifconfig bridge0 create
$ sudo brconfig bridge0 add tun0 add em0 up
The tunnel and bridge interfaces can also be configured at system startup by
editing /etc/hostname.tunN and /etc/bridgename.bridgeN,
respectively (see hostname.if(5)).
After configuring the virtual network we can use sudo to let root open the
tunnel device and then use sudo again to drop privileges and start qemu:
$ sudo sh -c "sudo -u $USER qemu -nographic -net nic -net tap,fd=3 \
-no-fd-bootchk -hda virtual.img 3<>/dev/tun0"
NOTE: sudo calls closefrom(2). In order to have more than one fd passed
tap interface, a line to sudoers akin to:
Defaults closefrom_override
then calling sudo via 'sudo -C 5 -u $USER qemu ..' is required.
See sudoers(5) and sudo(8) for details.
An alternative to the procedure described above is to have qemu set up the
network via ${SYSCONFDIR}/qemu-ifup. This is not recommended however, since
you would have to run qemu as root, and there is no way to drop from root
privileges at this point.
${SYSCONFDIR}/qemu-ifup contains some default settings that permit one to do
the following:
# qemu -net nic -net tap -no-fd-bootchk -hda virtual.img
It presumes you have a 'trunk0' interface you wish the tun(4) interface to
talk to. It presumes you want 'bridge0' to be used to bridge the two.
If you wish to over-ride these settings, setting the environment variables
ETHER and BRIDGE will over-ride these settings, respectively.
When starting qemu, the script attempts to output useful information, but
there are also error messages that occur as well. On my laptop, I want to
route / nat natively using pf and also have layer2 access to the qemu
networks. I thus have this as /etc/hostname.trunk101:
inet6 fe80::1c 64 lladdr 00:03:25:0d:7a:2c
inet 10.7.255.1 255.255.255.0
inet6 alias 2001:240:58a:45::1c
I have dhcpd configured to run on trunk101, and also run rtadvd. For qemu,
the startup looks like this:
# export ETHER=trunk101
# export BRIDGE=bridge101
# qemu -net nic,vlan=0,model=rtl8139,macaddr=52:54:00:12:35:00 \
-net tap,vlan=0 -vnc :0 -localtime -usb -usbdevice tablet \
-m 256 -no-fd-bootchk -hda virtual.img -monitor stdio
{tun0 (bridge101 <-> trunk101)brconfig: bridge101: No such process
brconfig: bridge101: No such process
}
(qemu)
The errors are normal and should be ignored. One can verify the networking
is properly configured by verifying the bridge interface:
$ brconfig bridge101
bridge101: flags=41<UP,RUNNING>
priority 32768 hellotime 2 fwddelay 15 maxage 20 holdcnt 6 proto rstp
designated: id 00:00:00:00:00:00 priority 0
tun0 flags=3<LEARNING,DISCOVER>
port 16 ifpriority 0 ifcost 0
trunk101 flags=3<LEARNING,DISCOVER>
port 6 ifpriority 0 ifcost 0
Addresses (max cache: 100, timeout: 240):
NOTE: When running multiple qemu sessions simultaneously on the same bridge,
care must be taken because the network mac address defaults to
52:54:00:12:34:56 for every qemu instance. To change this, observe
the macaddr= syntax in the above example and choose a unique lladdr
per qemu nic.
==> Mice
NOTE: Certain OS's work much better with the tablet usb device than
the normal ps2 mouse handling. See the above example for usage.
==> Serial Console
1. Installing OpenBSD via serial console is sometimes desirable. X may not
be available, and so on. There are two ways to accomplish this, both in
effect the same solution:
a. qemu -vnc :0 -serial stdio .. virtual.img -cdrom install43.iso -boot d
- this option permits you to use vnc from some system to connect to
the qemu instance and 'set tty com0' at the 'boot>' prompt.
- you may then disconnect vnc and use the terminal from which you
started qemu to do the install
b. qemu -nographic .. virtual.img -fda floppy45.fs -boot a
- this maps both the serial port and the (qemu) monitor prompt to
the terminal qemu was started on
- to flip between them, Ctrl-a c; see the qemu man page for other
commands that work in -nographic mode.
- preparation of the floppy image to force serial console mode is
straightforward:
vnconfig svnd0 floppy45.fs
mount /dev/svnd0c /mnt
mkdir /mnt/etc
echo set tty com0 > /mnt/etc/boot.conf
umount /mnt
vnconfig -u svnd0
.. be sure to choose 'yes' for setting com0 to be the serial console.
NOTE: OpenBSD poweroff does work with qemu, which actually causes qemu
itself to exit. This is a good thing, as it is currently not
possible to set what block device is booted from at runtime from
qemu. So if you start an installation booting from a cdrom, you
will always boot off a cdrom every time you reboot that qemu session
until you exit and start qemu again booting off the virtual hard
drive.
==> daemonized qemu
Sometimes you want qemu to start as part of a system script.
Adding to some of the above, the -daemonize option comes in handy,
as well as the telnet: designator for -serial and monitor. This
is a complete example that may be cut-and-pasted into rc.local:
hddir=/var/vm
USER=qemu
if [ -x ${TRUEPREFIX}/bin/qemu ]; then
echo -n 'Qemu: vmi386'
(
ifconfig tun0 link0
ifconfig bridge101 create
brconfig bridge101 add trunk101 add tun0 up
sh -c "sudo -u $USER \
${TRUEPREFIX}/bin/qemu \
-daemonize \
-nographic \
-net nic,vlan=0,model=rtl8139,macaddr=52:54:00:4e:62:8f \
-net tap,vlan=0,fd=3 \
-m 128 \
-hda $hddir/virtual.img \
-serial telnet:127.0.0.1:1010,server,nowait \
-monitor telnet:127.0.0.1:1011,server,nowait \
-no-fd-bootchk 3<>/dev/tun0"
)
echo "."
fi
NOTE: this presumes the user `qemu' exists, create it or set USER= to an
existing user to use this example.
