[CentOS] RHEL 6.1 beta

[Les Mikesell]

On 5/6/2011 7:53 AM, R P Herrold wrote:
>
>>> I'll try to blog about it, but once one knows the 'secret' it
>>> is not all that hard to predict -- This unit has three NICs
>>> (two onboard of the same type and an addon) which do NOT
>>> 'wander around' through reboots
>
>> But can you swap the disk into a new chassis of identical
>> hardware and have it come up with the right subnets on the
>> NICs in the corresponding physical positions?  Without
>> knowing MAC addresses ahead of time?
>
> Not without prior knowledge of the MAC addresses and edits,
> but it is still trivial to do.  With DHCP fabric on a physical
> segment, however, the devices will come up and be assigned
> IPs, the MAC addresses discerned [hooray for 'arpwatch' to
> make this trivial], and then may be revised into permanent
> working assignments without the need to resort to ILO or such

Supplying DHCP service with spare addresses on a bunch of remote subnets 
at a bunch of remote locations isn't really trivial just to be able to 
have a centos box work there.

> The process is stable and predictable enogh that these edits
> were done via just such a process, after a 'remote pair of
> hands' had physiclly installed the drive into a chassis at a
> datacenter that I cannot presently travel into and work at
> comfortable, due to an ankle injury some months ago.  The
> 'cold' aisles are too narrow for a stool or chair, and trying
> to work standing one-legged like a stork is too tiring

There are lots of reasons to want to be able to ship pre-loaded disks 
separately from the chassis or have remote support swap either one.  You 
don't have to cast it as a rare circumstance.  Consider the 'green' 
value of shipping drives instead of whole machines (which is what we 
usually end up doing for anything complicated).  I just hope whatever 
they are doing in 6.1 for non-random naming works on our hardware.  On a 
more practical note, I suppose I should have written something long ago 
that runs automatically after network startup that parses the ifcfg-ethx 
files, tries to ping the gateways through each interface and juggles 
things around until it works at least on the subnet we use for 
administration.  I had something like that mostly working when I did a 
'clonezilla image on dvd' rollout to upgrade a bunch of machines from a 
centos3 to 5 base, but in that case I had the previous mac/IP's to work 
with and was trying to match the old setup after the image came up on 
each one.  But, it failed on a few and I didn't bother to track the bugs 
down because it would have been hard to reproduce the circumstances.

-- 
   Les Mikesell
    lesmikesell at gmail.com