[CentOS] Setting GDM resolution without knowing the monitor specs

[Warren Young]

On Feb 21, 2019, at 12:00 PM, Warren Young <warren at etr-usa.com> wrote:
> 
> remotely talking someone through changing ifcfg-noisenoise via nano is a minor nightmare, especially now that Confusing Network Device Naming is the default.

A relevant war story might help here.

We were upgrading an old CentOS 5 box in the field.  They refused to ship it back to us, and they refused to buy a whole new box, but they had to have the newest software.

This being CentOS, “yum upgrade” wasn’t going to get us to CentOS 7.  What to do?

So, I logged into it remotely, poked around a bit, and got it to divulge the motherboard, CPU, etc. that we’d used on it, and I found that we had a nearly-identical box sitting around powered off locally, it having given us many years of useful service and then been retired.  Same motherboard, same CPU, same RAM, probably even bought within the same year.

So, I dropped a fresh system drive into that box, loaded CentOS 7 and all of our stuff onto it, configured the network and everything else under /etc the same as the box in the field, and shipped the drive out to the customer.

They put the drive in, booted it up, and it didn’t reappear on their network.  No remote access, no presence on the LAN.  It wouldn’t even ping.

After a ridiculous amount of remote troubleshooting, it turned out that these two motherboards — despite having the same model number and EFI firmware version — had a sliiiight difference: the first NIC appeared as enp2s0 and the second as enp3s0 on one motherboard, but as enp3s0 and enp4s0 on the other!  So, one network config wasn’t being applied, and the second was being applied to the wrong NIC.

And here I thought the point of [CNDN][1] was to make such replacements more reliable than the plug-and-pray logic behind ethN.

This is the sort of reason why I need non-Linux sysadmin types to be able to change IPs in the field.


[1]: https://en.wikipedia.org/wiki/Consistent_Network_Device_Naming