OpenBSD comes with a very simple, very nice hypervisor called vmd(8). This hypervisor is not a full featured as others, but it does a reasonable job of running VMs and makes it really convenient to spin-up a virtual environment for testing configurations. There are other articles on setting up a VM environment on OpenBSD. Its even covered in the FAQ which is a must read. And while this article and the others all show you how to start a VM, with this one I'll add the addition of how to get an OpenBSD guest to auto install.
To start with we need to setup the host system. First thing we need to do is update PF. While this isn't strictly necessary, I have wasted may moments troubleshooting a VM issue, when the problem was on the Host. To make networking on the VM easy, I SNAT all traffic from the VM environment out the physical interface.
Two things to note: 1) I utilize a new interface group VMS so that these rules will match any new interface that get created; 2) we will setup the VM's in a separate rdomain(4) so any traffic that is not remaining local will be tagged and moved to rdomain 0 so it can be SNAT'd.
Since we will be forwarding traffic from the VM environment to the outside world and visa versa we need to enable forwarding.
sysctl net.inet.ip.forwarding=1 sysctl net.inet6.ip6.forwarding=1
Next we need to create the interfaces we will use. A new rdomain and bridge interface will be created. NOTE: the lo5 interface gets created when the first interface with the new rdomain gets created.
ifconfig bridge0 rdomain 5 group VMS up ifconfig vether0 rdomain 5 group VMS ifconfig vether0 inet 100.64.0.1/24 up ifconfig bridge0 add vether0 ifconfig lo5 inet 127.0.0.1/8
Since we want to have our VMs automatically get an IP address when they start we need to setup dhcpd(8). This dhcpd.conf file will handout addresses out of the 100.64.0.0/24 netwok and deliver some dhcp options that we need to tell our VM's to autoinstall. We have also specified the MAC address of the VM. This allows dhcp server to send a hostname to our VM when it's installing allowing us to set the name. (This could also be done in the install.conf file but then we would need to have a separate install.conf file for every VM. This way we can keep one file and just update the name in dhcpd.conf
Now start the dhcp server in rdomain 5.
rcctl enable dhcpd rcctl set dhcpd rtable 5 rcctl set dhcpd flags vether0 rcctl start dhcpd
We will also need to serve some files from the httpd(8) server. Using the simple config below, setup the httpd server to start on rdomain 5.
rcctl enable httpd rcctl set httpd rtable 5 rcctl start httpd
Now copy the install.conf below to the web root /var/www/htdocs/.
Now we need to add the OpenBSD install files to the web directory.
mkdir -p /var/www/htdocs/pub/OpenBSD/7.1/amd64 for i in `echo "SHA256 bsd bsd.mp bsd.rd base71.tgz comp71.tgz game71.tgz man71.tgz xbase71.tgz xfonts71.tgz xserv71.tgz xshare71.tgz index.txt"`; do ftp -o /var/www/htdocs/pub/OpenBSD/7.1/amd64/$i https://cdn.openbsd.org/pub/OpenBSD/7.1/amd64/$i done
Optional: If you want to further customize the install you can add a site71.tgz or hostname-site71.tgz file to the web directory. If you do, you'll need to remake the index.txt file. This is easily accomplished below.
ls -lT > index.txt
Finally we need the vm.conf configuration file for vmd(8). Notice that there are 2 VM definitions. The build-vm1 definition is only used when building the new VM. Also notice that the MAC address is the same one that was specificed up in the dhcpd.conf file. The vm1 definition is the one that will run the VM after it's been created.
Now enable vmd(8) and start it.
rcctl enable vmd rcctl start vmd
To make sure the configuration loaded correctly use vmctl(8) to show the VM status.
Now we can finally build the VMs.
First step is to create the disk. An assumption is being made the the VM disk images will be stored in the /home/vms directory.
vmctl create -s 5G /home/vms/vm1.qcow2
Build the VM
Now start the build process.
vmctl start -c -B net -d /home/vms/vm1.qcow2 -t build-vm1 vm1
This will start the VM build process. The -c option attached the current terminal to the the console of the building VM. If all goes well the only key that will need to be pressed is the one at the end of the build process to exit the VM.
Run the VM
After the VM is built, to start it just run the vmctl(8) command again.
vmctl start vm1
This will start the VM but not attach the console to the existing terminal. To attach to the console you can use the vmctl command below. To exit the console use ~. escape sequence.
vmctl console vm1
Or you can ssh to the VM. Check the /var/log/daemon log file to see what IP was assigned to the VM and then ssh to the VM. Note that the VM is running in a separate rdomain so to ssh from that rdomain use the route(8) command.
route -T 5 exec ssh [email protected]
This is just a simple tutorial on how to get a VM up and autoinstalled on OpenBSD hypervsor. Pleas let me know if there are anything I might have missed.