Mandatory Access Control

[ner0]

Hello,
Where can i find good tutorial / hints / document (or other) about MAC and
maclabels.
I asked on usenet, i searched in google and there is nothing any good
resources.
Why itsn't have good documentation?


I got first small problem:
# touch 1
# getfmac 1
1: biba/high
# setfmac biba/low 1
setfmac: labeling not supported in 1
#

why?
I did (tunefs -l enable), I have MAC option in kernel, and mac biba enabled
in loader.conf
I only try to build very secure system but I don't know how to use mac.
Thanks for any help.

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ner0