After entering: mdadm --create /dev/md0 --level=1 --metadata=0.9 --raid-devices=2 /dev/sdb1 /dev/sdb2 one would then enter: watch cat /proc/mdstat which will show one the progress/status of the mdadm command. Once it it’s 100% one would then select the CTRL + c keys to close the status and return to the command prompt where you can continue with the remaining steps.
Couple of additional comments. You can choose to use one of the two following files to extract.
Original_v03.04.01-230.tar.gz: https://fox-exe.ru/WDMyCloud/WDMyCloud-Gen1/Backups/original_v03.04.01-230.tar.gz
Original_v03.04.01-230.tar.gz: https://fox-exe.ru/WDMyCloud/WDMyCloud-Gen1/Backups/original_v04.01.02-417.tar.gz
If you run into trouble with the kernel.img in original_v04.01.02-417 being too large for the sdx5 partition when you issue the dd command. Delete the files extracted from the original_v04.01.02-417 file and extract/use the files from original_v03.04.01-230.
Once you reconnect the My Cloud board to the hard drive and boot/power it on, if it doesn’t boot (after a long wait) to a blue front LED, it might boot to a red front LED. If it does boot to a red front LED try accessing the My Cloud Dashboard (http://wdmycloud or http://wdmycloud.local) and access the Settings page. Then select Quick Restore from the Utilities menu. That should fix the fail to mount content partition error that causes the red front LED.
Once you have a blue front LED one can then proceed to upgrade to the latest My Cloud firmware. If one used original_v03.04.01-230 they can upgrade to v04.01.02-417 before upgrading to the very latest My Cloud firmware. Not sure if one can go from the older v3 firmware direct to the very latest firmware, but one could always try rather than doing the interim step of going from v3.x to v04.01.02-417.
https://community.wd.com/t/wd-my-cloud-v3-x-v4-x-and-v2-x-firmware-versions-download-links/148533
04.01.02-417 (12/17/2014) Firmware: http://download.wdc.com/nas/sq-040102-417-20141211.deb.zip
Latest My Cloud v4.x firmware: http://download.wdc.com/nas/sq-040500-334-20190221.deb
