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