Well, the upgrade has been sucessful. I believe this document decribes what I was experiencing. Additionally, the process took MUCH longer than the estimated time to upgrade the control station Linux. Since the CS was unresponsive and based off of what I was seeing, I thought the kernel was hosed. I did still have to intervene and manually reboot, so the upgrade process did have something wrong. After a little over an hour, I could finally reach the CS. When I resumed the upgrade, it tried upgrading the CS Linux again, but went by in just a few seconds. I wish EMC had more documentation available to customers for those willing to look into it. I understand why they want certain tasks to be performed by their techs, but sparse documentation is more dangerous if one has only part of the procedure. Thank you to those who provided inputs. I will try to reciprocate as best as I can.
Happy (early) New Year. I'm new to EMC, but I've immersed myself in the material over the past few weeks. I've found many answers on these forums and I now find myself reaching out and hoping somebody can help me.  I have three Celerra NS20s with CLARiiON CX3-10 backend storage. To take advantage of newer features, I backed up all of the important data from one and used USM to perfom a DART upgrade from 5.x to 6.x (I don't have the exact version in front of me, but it was an approved direct upgrade path according to the compatability documentation. All health checks were good in the pre-upgrade check). During the upgrade, I ran into an issue that I posted a solution on in this thread. Basically, the system had to be manually restarted (reboot -f), but I made sure everything was okay in the log (/var/tmp/upgrade.log). After rebooting and starting USM again, it picked up where it left off and continued on its happy way. Eventually, it got to the step where it had to upgrade the Control Station Linux. Everything went fine from what I could tell, but eventually USM came back and stated that it was taking longer than expected to reboot the Control Station. I wasn't able to ping the IP at all, so I went to the server room and hooked up a monitor and keyboard to the Control Station to see what was going on. It was attempting to boot, but was stuck on loading initrd.img. I rebooted several times, but it hits this right after GRUB tries to boot. In addition to the package for USM, I had a copy of the DART software on DVD. I booted into this and tried to do a repair, but I'm having the same problem. Can I reload the Control Station Linux from scratch without losing my data? I'm not entirely clear if a fresh load will remove any data or what will need to be reconfigured. What other options do I have? All of my storage is still available, but I can't manage it.  These were set up a while ago by a tech, but they have been moved to new location in a secure government building, so getting a tech out isn't a viable option at this point.  TL;DR - Attempted a DART upgrade and now I'm stuck at boot trying to load initrd.img. A tech coming out is unlikely.  Any input/advise is greatly appreciated. Thank you in advance.
Boot issue after DART upgrade attempt