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.