Network Card Naming Issue

[Bill Davidsen]

Les Mikesell wrote:
> Bill Davidsen wrote:
>>
>> Actually, no. The method is to use UUID and totally ignore hardware 
>> names. That's what current /etc/fstab and /etc/mdadm.conf do these days.
>>
>>> Right now, the key hardware components are remembered by udev.  As 
>>> this new method matures, it will become easier to maintain/remove 
>>> hardware.  But think of the alternative!  The old way might be ok for 
>>> single drive, single interface systems, but not otherwise.
>>>
>>> There are many of us who remember the 'bad old days' when this issue 
>>> was capable of destroying months of work!
>>>
>> The hal stuff was written by people who were wedded to matching the 
>> same device to the same name. Putting MAC address, UUID, or serial 
>> number in as the key is far more reliable, and allows people to to 
>> have a single place to specify the match. Having to beat up sysconfig 
>> and hal to change a failed device is not conducive to good system 
>> administration.
>>
>> Your points are well taken, but I consider hal keeping it's own ideas 
>> instead of using sysconfig to be a bug, not a feature.
> 
> You do need to be able to move parts around as well as replace old parts 
> in an existing system.  And you need to be able to do image copies of 
> drives.  What happens if you put disks with duplicate labels (for years 
> they wouldn't boot...) or uuids into the same machine?   What if you put 
> disks that previously used to be the same-numbered md? device from 2 
> different machines into the same box?  It has been a while since I tried 
> that, but it wasn't pretty.
> 
The md device number seems not to be an issue. Using a non-unique UUID on a 
system is the same level as swapping two hard drives and using the physical 
device name to determine how they're used, if you make an effort to shoot 
yourself in the foot you will wind up with a hole in your shoe. Deliberately 
creating a condition where the information used to tell hardware apart is 
ambiguous is dubious practice at best.

> What if you want to replace your current eth0 with a different card and 
> shift the use of the existing one to a different subnet?
> 
Have the info in one place, sysconfig, not sysconfig and hal keeping their own 
idea of reality. Being able to set this in one place is good, assuming that two 
places will always match is unrealistic. People screw up, restores happen, one 
place is right or wrong, but never maybe.

> And all of this gets in the way when you need to restore your backups 
> onto a similar but different box.
> 
If you make physical backups of drives that is the least of the problems. The 
UUID isn't backed up using by-file backup, so conventional backups by tape or 
rsync aren't a problem. Finding that two drive made a few months apart, with the 
same part number, are actually slightly in size is painful reality, the only 
things I backup with a physical backup are VM images, and usually not those either.

-- 
Bill Davidsen <davidsen at tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot