green LED flashes 4 times - rpi B 3+ but works USB-boot

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I have for a long time run a rpi 3B+ by having


on the SD card
and all application specific stuff on a small
(80 GB) USB-disk 2.5" spinning metal

So the other day I bought a 120 GB SSD disk at amazon  

And I use gparted on another Linux box to
- clean out the new SSD
- copy /boot from SD card and paste on SSD
- copy / from sdcard  and paste on SSD
- copy /bnlbot from old USB-drive and paste on SSD

The whole procedure was very smooth - I did not know of copy/paste  
within gparted before.

in /boot/cmdlie,txt I changed the root UUID
in /etc/fstab I did the same, changing UUID and PARTITIONUUID
to new values.

Nice - unmount from PC and put SSD in rpi via USB - with no SD card
Power on

LED flashes 4 times - seem to mean

* 4 flashes: start.elf not launched

But - the PI works,
I can SSH to it
the database works,  my applications has started.

dmesg confirms boot from USB (well there is no SD-card so)

Everything but the LED seems fine

Why does it flash?
I cannot google an answer to make it not flash


Re: green LED flashes 4 times - rpi B 3+ but works USB-boot

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 From the above reference:

Note that 4-flashes may point to a defective SD-card holder, if one or  
more of the data contacts is intermittent it can lead to this problem.

"No SD card" probably can't be differentiated from "Bad SD card holder"  
as no contact with SD card.

Chris Elvidge

Re: green LED flashes 4 times - rpi B 3+ but works USB-boot
Den 2021-01-13 kl. 15:07, skrev Chris Elvidge:
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Well, yes, hmm how could I miss that?

the boot order is at  

with a comment

"If there is no SD card inserted, the SD boot mode takes five seconds to  
fail. To reduce this and fall back to USB more quickly, you can either  
insert an SD card with nothing on it or use the GPIO bootmode OTP  
setting described above to only enable USB."

So I halted, inserted a small empty one and boot and now no more  
flashing. Thanks


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