Debian 6 will also be available with the FreeBSD kernel. Why did they decide to to that and why should I use it?
I think the most compelling reason would be to run ZFS under a familiar GNU/Linux userspace.
Debian kFreeBSD is officially considered a technical preview right now. This means it works but is not completely ready for production use.
If you just want a usable system stick with Debian Linux for now.
Once it graduates from technical preview status, you may want to reexamine it if you have needs that are better fulfilled by BSD than Linux, such as ZFS and the OpenBSD Packet Filter (pf).
Debian does not target a specific kernel. Debian GNU/Linux is just one variant (the most popular and advanced). There are also Debian GNU/NetBSD, Debian GNU/Hurd, Debian GNU/Darwin, and as you mentioned Debian GNU/kFreeBSD (and perhaps more). Porting Debian to non-Linux kernels is useful for people (users, system administrators, system developers, etc) who are using/developing a non-Linux kernel but would like to take advantage of the Debian (
debconf, the policy) and GNU (
gdb, etc) tools.
Actually based on my experience with Debian/kFreeBSD, you shouldn't:
I encountered all of this while trying to set up a backup system with GNU/kFreeBSD and ZFS. In the end I threw the towel and went with zfs-fuse on standard Debian. Works very well. I have just replaced a failing hard disk yesterday and all went wonderfully smooth (link in french: http://meta.libera.cc/2012/09/linux-zfs-et-disque-sata-remplacement.html )
- first of all there is no specific documentation concerning Debian/kFreeBSD. You get either the Debian documentation or the FreeBSD documentation. Problem occurs when you sit in the middle you don't know where to look for.
- no user-support oriented mailing list, only a dev mailing list http://lists.debian.org/debian-bsd/2012/09/threads.html
- firmware for devices is not packaged for kFreeBSD, meaning many NICS will not work. see: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=642468
- keyboard setup is broken is the installer: how nice when you set discover that you can't login after your first install (not everybody hese uses QWERTY you know ...)
- many enterprise grade packages are not working (Amanda, ldap integration) see: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=661697
the install CD is buggy in rescue mode: if you get
mount /dev/da4s1 /mnt mount: mounting /dev/da4s1 on /mnt/failed: No such file or directory
it means you should interstand you have to do
mount -t ufs /dev/da4s1 /mnt
to get it working ...
- if you know BSD and Linux you get confused about which synthax you should use for base commands. For instance fdisk is Linux-like but kbdcontrol, ifconfig, mkfs are BSD-like
and most important the project name is much too difficult to write :) uppercase then lower then upper then lower then upper then lower ...
All in all maybe a good idea, but let's wait it leaves the alpha stage ...
Debian is a "Universal Operating System", the kFreeBSD is another example to this. They experimenting with other kernel too, like Hurd, Darwin and others.
The answer, why the FreeBSD's kernel is the most used along with the Linux kernel, is the richness of that kernel. It's best features ZFS filesystem, Jail virtualization subsystem and others.