[Lxc-users] updated lxc template for debian squeeze - with attachedscript ; )

[Michael H. Warfield]

On Fri, 2011-03-11 at 16:47 +0100, John Soros wrote: 
> > Can someone explain to me why we can't simply use a block of addresses
> > with the 0200 (local administration) bit or'ed in.  Out of 48 bits of
> > addressing, we can use 46 bits of them for anything we want as long as
> > that bit is set and the 0100 bit (multicast) is clear.  By the
> > standard, those are locally managed and allocated MAC addresses that
> > are not guaranteed to be globally unique.  They don't even need to be
> > unique in an entire network, only on the local subnet.  Use any
> > convention you want.  Stuff the 32 bit IP address of the host in the
> > lower 32 bits and you've still got 14 bits worth of assignable
> > addressing per host. That's what that bit is intended for.
> > 
> > > - Walter
> 
> isn't that what the script does? :
> ==snip==
> rndbit=""
> while [[ $rndbit != "2" && $rndbit != "6" && $rndbit != "A" && $rndbit != "E" ]]; do
>   rndbit="$(hexdump -n 1 -v -e '/1 "%02X"' /dev/urandom |sed 's,^.,,g' |tr -d '\n')"
> done
> macaddr=$(echo -n "0${rndbit}"; hexdump -n 5 -v -e '/1 ":%02X"' /dev/urandom)
> ==/snip==
> I agree it's not as pretty as or'ing a random mac with 0200 but the
> result should be the same. Of course if someone finds a way to bitwise
> or on the commandline i'll be happy to update the patch. 
> Thanks,
> (whoops, ok so how to be sure the adress is not multicast)

Ok...  Does this not work for you?  Works for me...

[mhw at canyon ~]$ declare -i BYTE=$(( 0xC1 & ~ 3 | 2 ))
[mhw at canyon ~]$ echo ${BYTE}
194
(0xc2)

Since you're using the "[[" expression, I think you're pretty locked
into bash are you not?

> --
> Sticky bits on disk.

Regards,
Mike

-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
 PGP Key: 0x674627FF        | possible worlds.  A pessimist is sure of it!
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