It seems the issue is this:
- 5.9.5. Upgrade failed, CLI doesn't become available anymore
If for a certain reason the upgrade was successful and the Steelhead appliance comes back but doesn't allow CLI or GUI access: This means that a back out of the upgrade cannot be performed.
The way out of this would be to hook up a serial console to the Steelhead appliance and reboot the device. After the BIOS, the Grub bootloader will show up with the text Press any key to continue.... After pressing a key, the two boot partitions are displayed. Use the v and the ^ to select the pre-upgrade boot image and press enter. After the downgrade, access to the Steelhead appliance should be available again and the Riverbed TAC should be involved to determine why after the upgrade the connectivity failed.