Edit: Backup everything. Then test it.
Originally posted December 13, 2016 on AIXchange
A customer had an HMC issue. There were no backups, so the HMC had to reinstalled from scratch. There wasn’t any documentation either, meaning that the customer had no idea what the network settings should be.
Stop reading for a moment and put yourself in this uncomfortable picture. Do you have backups of your HMC? Is your network information well-documented? Is it documented at all? If you had to rebuild your HMC right now, could you?
Luckily for my customer, they had a simple environment, and their HMC was onsite so they could visually inspect their equipment. One network cable was directly plugged into the HMC port of their single POWER8 system; another connected directly from their HMC into their switch. Knowing this, it was simple enough to determine which port should be the private network and which should be the open network.
What about you? Do you know which physical cables from your HMC are used for which network in your environment?
Back to our story: Configuring the open network was straightforward, and my customer was soon able to use the GUI to connect to the HMC. Once the firewall settings were fixed and the ssh port opened, they could login to the HMC via the command line.
Their next issue was getting the HMC to recognize their managed system. They picked a range of IP addresses to use for their DHCP server, but how would they know which IP address was in use by the managed system?
After looking over this documentation, they ran lshmc -n -F clients. That provided the IP address that had been served out by their DHCP server.
From there, it was a snap to add the managed system, since they knew the address it was using. But what about the password? No one in the group was around when it was originally set up, so no one knew the password for the managed system.
Again, ask yourself: Do you know the passwords for your managed system, ASMI, etc.?
A few failed guesses (naturally) resulted in an authentication failure message. The HMC went into a firmware password locked state. With nowhere else to turn, they did a web search and found this IBM Support document with this helpful bit of information:
Note: The default password for user admin is admin.
So they tried “admin.” Unsurprisingly, that default was still in place. The customer was able to connect to their managed machine. Everything looked as they expected.
I know this is basic, but even the basics can mess you up if you haven’t thought about them, particularly if you weren’t the one who setup your HMC.
Should you ever find yourself in a similar predicament, here’s a pretty good reference HMC setup.