Question about NIC link state initialization

[Steve Polyack]

On 6/30/2011 6:49 AM, Daniel Feenberg wrote:
>
>
> On Wed, 29 Jun 2011, perryh at pluto.rain.com wrote:
>
>> Steve Polyack <korvus at comcast.net> wrote:
>>
>>> ... An occaisional fat-finger in /etc/fstab may cause one to
>>> end up in single-user mode ... some of these systems have a LOM
>>> (lights-out management) controller which shares the system's
>>> on-board NICs ... when the system drops out of init(8) and into
>>> single-user mode, the links on the interfaces never come up,
>>> and therefore the LOM becomes inaccessible.
>>>
>>> ... all one has to do is run ifconfig to cause the NIC's links to
>>> come up ... why do we have to run ifconfig(8) to bring the links
>>> up on the attached interfaces?
>>
>> When trying to troubleshoot a problem that was known or suspected to
>> involve the network or its hardware, one might not _want_ the NICs
>
> Well, maybe, but if the system needs to boot into multi-user mode for 
> the LOM to be available, what is the need for the LOM? At that point 
> you can do everything you might need through the OS interface. Can I 
> ask what is the brand of this so-called LOM? Is there any 
> documentation implying something more useful? Do they describe doing a 
> bare metal install of an
> OS?

They are the Dell Remote Access Controllers (DRACs).  Now, they do have 
their own dedicated NIC, which we use for anything that really needs the 
attention.  However, the shared feature saves us a switchport per server 
we use it on.  When both on-board NICs are cabled (i.e. for lagg(4) 
failover), then the DRAC's shared NIC mode *also* supports automatic 
failover between both on-board NICs.  This doesn't help however if the 
operating system never turns on the links to either on-board NIC.

I was able to "fix" the single-user mode behavior (which I agree, isn't 
necessarily broken) and get it to bring up the links by simply patching 
init(8) to call system("/sbin/ifconfig") before prompting for the 
single-user shell.  It works, but I feel dirty.

- Steve