FreeBSD as DomU/Guest HOWTO
1) Kip Macy's brief instructions and get the necessary files from that site.
Or:
2) Alternative HOWTO and install files at this site.
FreeBSD DomU on Debian GNU/Linux Dom0 with Xen 3.0.3
I wanted to migrate an existing FreeBSD system to Xen. The first part included creating dd of the hard drive image. Than i've downloaded a xen domU kernel and the appropriate config from http://www.yuanjue.net/xen/howto.html.
The FreeBSD kernel refused to boot with the following error:
Error: (22, 'Invalid argument') ERROR: Initial guest OS requires too much space (0xc08MB is greater than 256MB limit)
The problem was, that Xen 3.0.3 requires a VIRTUAL_BASE=0xC0000000 option in the __xen_guest section of the kernel binary. You can view the section of your kernel binary using
objdump -j __xen_guest -s freebsd-XENU
and replace it using
objcopy -R __xen_guest freebsd-XENU objcopy --add-section __xen_guest=file_with_new_contents freebsd-XENU
(thanks to this post). The contents of the section is basically a string, but it has to be zero terminated.
The second problem i faced was that from the FreeBSD domU TCP connections worked to the outside world, but I was unable to establish a TCP connection to other (Linux) domUs on the same machine. The setup uses bridged networking. The solution that worked originates from and is explained in this post:
FreeBSD domU> ifconfig xn0 -txcsum All Linux domUs> ethtool -K eth0 tx off
Later i faced another problem. Multithreaded programs crashed in pthread_self. Beeing a FreeBSD newbie i learned that FreeBSD provides multiple threading libraries and that you can choose which one apps should use editing /etc/libmap.conf. The user space threads library libc_r worked for me and is good enough for a developement system, but its performence is probably suboptimal.
Notes
Ariel E. Antigua writes:
I was reading in the xen-users list and read a few emails from people that cant boot FreeBSD as a domU using the Kip Macy instructions at http://www.fsmware.com/xenofreebsd/5.3/ i have the pleasure to inform that his work is still usefull, the only thing that stop me booting that FreeBSD domU image was i forget to add de ufs: root mount device but using this config http://lists.xensource.com/archives/html/xen-users/2005-09/msg00594.html i finally have the domU boot and runing.
PS: My dom0 is Debian Sarge with Xen 2.0.6 , i get this dom0 running thanks to this guide http://www.option-c.com/xwiki/Xen_Debian_Quick_Start
I hope this can help someone else having troble with FreeBSD as domU.....
Thanks Kip Macy for the FreeBSD/domU howto.. 
