Booting single-user on a pi3b

Some time ago I retired a Stretch installation microSD that had
been running on a Pi3b+. There was nothing wrong with it, I just
wanted to upgrade the card and move to Buster. I saved the card
to use as a test boot medium, since it had worked very reliably
for a couple years.
However, when the card is inserted in a (somewhat older) pi3b
(not a plus) the boot process sticks at the line
"Started create volalatile files and directories"
after which all progress seems to stop.
Is there some way to make the Pi boot to single-user mode?
All I really want to do run the vcgencmd to check if the
boot from usb OTP is set. Still, it's puzzling that the
card, which booted faultlessly in the 3b+, seems to be
getting stuck in the older Pi.
Thanks for reading, and any ideas!
bob prohaska
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bob prohaska
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Add ' single' to /boot/cmdline.txt (on the same line as the existing stuff)
If it won't boot, pull the SD card and edit the file on another machine.
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Done, but the machine doesn't give a prompt to enter single-user.
It flashes the rainbow screen, blacks out and puts up the four raspberries, then starts scrolling boot messages. I tried hitting spacebar repeatedly to interrupt boot starting before the rainbow screen but the system just kept going, finally stalling with "starting update UTMP about system boot/shutdown"
At no point is there any serial console output. The console works with FreeBSD at 115200 bps, which I think is the same as Raspbian. Is some non-default setting required to turn on the serial console? I'm monitoring pins 8 and 10, per the GPIO pinout guide.
It's especially odd there's no output from u-boot on the serial console. I'd expect to see that before anything else.
Thanks for reading, and your help!
bob prohaska

Reply to
bob prohaska
It turns out adding uart_enable=1 to config.txt did the trick. The system comes up with a serial console, the hangup seems to be with the video system. Formerly it was used with a 1080 display and apparently gets stuck with 1920x1200.
No matter. Running bob@raspberrypi:~$ vcgencmd otp_dump | grep 17: 17:3020000a
gives the correct result, so the machine is configured to boot from USB. Back to the old thread......
Thanks for reading,
bob prohaska
Reply to
bob prohaska

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