This section describes how to install FreeBSD in exceptional cases.
This type of installation is called a “headless install”, because the machine that you are trying to install FreeBSD on either does not have a monitor attached to it, or does not even have a VGA output. How is this possible you ask? Using a serial console. A serial console is basically using another machine to act as the main display and keyboard for a system. To do this, just follow the steps to create an installation USB memstick, explained in Section 2.3.7 or download the correct installation ISO image see Section 2.13.1.
To modify these media to boot into a serial console, follow these steps (If you want to use a CDROM you can skip the first step):
Enabling the Installation USB Stick to Boot into a Serial Console
If you were to boot into the USB stick that you just made, FreeBSD would boot into its normal install mode. We want FreeBSD to boot into a serial console for our install. To do this, you have to mount the USB disk onto your FreeBSD system using the mount(8) command.
# mount /dev/da0a /mnt
Note: Adapt the device node and the mount point to your situation.
Now that you have the stick mounted, you must set the USB stick to boot into a serial console. You have to add to the loader.conf file of the USB stick file system a line setting the serial console as the system console:
# echo 'console="comconsole"' >> /mnt/boot/loader.conf
Now that you have your USB stick configured correctly, you must unmount the disk using the umount(8) command:
# umount /mnt
Now you can unplug the USB stick and jump directly to the third step of this procedure.
Enabling the Installation CD to Boot into a Serial Console
If you were to boot into the CD that you just made from the installation ISO image (see Section 2.13.1), FreeBSD would boot into its normal install mode. We want FreeBSD to boot into a serial console for our install. To do this, you have to extract, modify and regenerate the ISO image before burning it on a CD-R media.
From the FreeBSD system where is saved the installation ISO image, for example FreeBSD-8.1-RELEASE-i386-disc1.iso, use the tar(1) utility to extract all the files:
# mkdir /path/to/headless-iso # tar -C /path/to/headless-iso -pxvf FreeBSD-8.1-RELEASE-i386-disc1.iso
Now you must set the installation media to boot into a serial console. You have to add to the loader.conf file from the extracted ISO image a line setting the serial console as the system console:
# echo 'console="comconsole"' >> /path/to/headless-iso/boot/loader.conf
Then we can create a new ISO image from the modified tree. The mkisofs(8) tool from the sysutils/cdrtools port is used:
# mkisofs -v -b boot/cdboot -no-emul-boot -r -J -V "Headless_install" \
-o Headless-FreeBSD-8.1-RELEASE-i386-disc1.iso /path/to/headless-iso
Now that you have your ISO image configured correctly, you can burn it on a CD-R with your favorite burning application.
Connecting Your Null-modem Cable
You now need to connect a null-modem cable between the two machines. Just connect the cable to the serial ports of the 2 machines. A normal serial cable will not work here, you need a null-modem cable because it has some of the wires inside crossed over.
Booting Up for the Install
It is now time to go ahead and start the install. Plug in the USB memstick on the machine you are doing the headless install on, and power on the machine. If you are using a prepared CDROM, power on the machine and insert the disk to boot on.
Connecting to Your Headless Machine
Now you have to connect to that machine with cu(1):
# cu -l /dev/cuau0
On FreeBSD 7.X use the following command instead:
# cu -l /dev/cuad0
That's it! You should now be able to control the headless machine through your cu session. It will load the kernel and then it will come up with a selection of what kind of terminal to use. Select the FreeBSD color console and proceed with your install!