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

[John Soros]

Hi,
i have tried to find an rfc about this but have failed, instead, the
only (serious/credible) documentation i could find was
http://wiki.xen.org/xenwiki/XenNetworking#head-d5446face7e308f577e5aee1c72cf9d156903722 ,
so i updated the script accordingly, here is the updated patch.
again,
Signed-off-by: John Soros <johnny at r0x0r.me>


--
the router thinks its a printer.


On Fri, 25 Feb 2011 09:03:55 +0100
Jäkel, Guido <G.Jaekel at dnb.de> wrote:

> Dear John,
> 
> > - generate random mac address for the guest so it gets always the
> > same lease from a dhcp server
> 
> You suggest doing this by
> 
> 	macaddr=$(echo -n 00; hexdump -n 5 -v -e '/1
> ":%02X"' /dev/urandom)
> 
> 
> 
> I think this is a "little bit to random". The german Wikipedia tells
> at  http://de.wikipedia.org/wiki/MAC-Adresse  about a reserved MAC
> range for private use (sorry, it's not in corresponding the English
> article):
> 
> 	["Neben der OUI existiert auch ein kleiner Adressbereich (IAB
> - Individual Address Block), der für Privatpersonen und kleine Firmen
> und Organisationen vorgesehen ist, die nicht so viele Adressen
> benötigen. Die Adresse beginnt mit 00-50-C2 und wird von drei
> weiteren Hex-Ziffern gefolgt (12 Bits), die für jede Organisation
> vergeben werden. Damit verbleibt der Adressbereich innerhalb der Bits
> 11 bis 0 nutzbar wodurch 212 = 4096 individuelle Adressen möglich
> sind."]
> 
> 
> 
> Maybe we should take respect to this and we should use
> 
> 	macaddr=$(echo -n "00:50:C2"; hexdump -n 3 -v -e '/1
> ":%02X"' /dev/urandom)
> 
> for this. Another approach is to derive it from the designated name
> of the container (i.e. $hostname in terms of the script). Because
> there might be typical clustering naming schemes based on a name and
> some digits, I suggest to select the first and the last two
> characters of the hostname (filled by random for the unlikely case of
> a hostname shorter than 3 chars)
> 
> 	echo -n "00:50:C2"; echo "${hostname:0:1}${hostname: -2}
> $(head -c 3 /dev/urandom) " | hexdump -n 3 -v -e '/1 ":%02X"'
> 
> 	-> 00:50:C2:<first>:<nextlast>:<last>	filled by random
> 
> 
> 
> @Daniel: Because this will have a common use for all, it might be
> included into the lxc-conf parser
> 
> 	["lxc.network.hwaddr: the  interface mac address is
> dynamically allocated by default to the virtual interface ...]"
> 
> 
> We maybe should have a special keyword for a "derived" semi-static
> MAC that would not change at every startup of the container but may
> be calculated by the formula given above.
> 
> 
> Guido
> 
> 
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