On 23/10/2019 16:52, Mike Scott wrote:
> I've used rsync -n to cross-check the two root partitions - apart from
> inconsequential stuff (/tmp, cups) they're the same.

That will check the file contents are the same, but there could be
differences in permissions if it wasn't copied preserving attributes
with as Chris mentioned. I suggest following his advice rather than mine
- redo the SD card to USB copy with rsync -vaxHAXP which should make an
identical copy.

Although they way I've always made USB drives for the Pi, is a copy a
working SD card to it using dd, so the contents are intially 100%
identical. I then expand the partition on the USB device to the desired
size, edit /etc/fstab on the USB, and modify cmdline.txt on the SD card.

> I don't know if it makes a difference, but I /think/ this is a plain
> pi3B. Other partitions are fine on the HD, but the only way I can make
> this go is by having root on the SD card.

There's no reason why this wont work on the 3B. I've used a USB to SATA
and a SSD with a 3B, 3B+, 4B with no changes to the setup when migrating.

> I'm beginning to wonder if there might be something odd about the USB
> connection: I'm using a spare sata drive in a usb adapter. It works ok
> on ubuntu and freebsd desktop machines though. I don't have another
> spare to try.

I have several different USB3 to SATA2 and USB3 to SATA3 and they all
work with the Pis. There isn't any noticable difference in performance
between SATA2 and SATA3 on the USB2 3B and 3B+, but is a bit quicker on
the USB3 4B.

---druck

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