Rpi 3B+ crashes with SSD

Troubleshooting
5

From our side we do not recommend to run external USB devices without own PSU as we had quite some reports related to power consumption in such cases.

Anyway to be able to have a look to the system logs before the crash happen, you would need to make them permanent. Persistent system logs could be enabled as follows:

dietpi-software uninstall 103 # uninstalls DIetPi-RAMlog
mkdir /var/log/journal # triggers systemd-journald logs to disk
reboot # required to finalise the RAMlog uninstall

Then you can check system logs via:

journalctl

which will then show as well logs from previous boot sessions. To limit the size, you can additionally e.g. apply the following:

mkdir -p /etc/systemd/journald.conf.d
cat << '_EOF_' > /etc/systemd/journald.conf.d/99-custom.conf
[Journal]
SystemMaxFiles=2
MaxFileSec=7day
_EOF_

This will limit logs to 14 days split across two journal files, so that with rotation you will always have between 7 and 14 days of logs available.