This appears to be an intermittent, perhaps timing related problem. However, it may also be related to the use of the backstore feature.!! Cannot find device with /sysrcd.dat. Retrying...
>> Attempting to mount device: /dev/sda
>> Attempting to mount device: /dev/sda1
>> Attempting to mount device: /dev/sda2
>> Attempting to mount device: /dev/sda3
>> Attempting to mount device: /dev/sda4
>> Attempting to mount device: /dev/sda5
>> Attempting to mount device: /dev/sdb
>> Attempting to mount device: /dev/sdb1
!! Cannot find /sysrcd.dat on devices
!! Running a mini shell (cannot complete the boot process)
/bin/sh: cant access tty; job control turned off
Update: It appears (in my case at least), anytime another usb hdd device is present on the host system when doing a reboot, it may occupy /dev/sdb1. So when srcd attempts to find /sysrcd.dat on a usb device, if it cant find it on /dev/sda?, it keeps trying /dev/sdb1, and then gives up.(?) It seems to me all the block devices should be visible to srcd during boot-up, so it ought to be able to find the one with the 'SYSRESC' label, and mount that one on the first available device. If srcd only works when /dev/sdb1 is available for the stick, that could be a problem.
I created a sysrcd.bs backstore loop file system using the provided utility on the root of a usb hard drive. I plugged it in to the machine I wanted to work on, but did not specify the 'ar_alldev' option in the boot parameters. Sometimes srcd would boot successfully. Because I was using an autorun0 file on the usb stick, I tried removing that, and it appeared to solve the problem in some cases, but not consistently.
Apparently, the specific reason for the boot failure is that the external usb hard drive gets assigned to /dev/sdb1, and this prevents the boot sequence from completing. So, if you want your backstore to be resident on an external removable hard drive, rather than the stick itself, you may run into this problem.