How to bring the HDD to the state of "As from the store"?

Question

linux

Good afternoon (night)
There is a HDD, which used to be part of the software Raid-1 on Debian 9, now this HDD is planned to be installed to replace the failed disk, also software Raid-1, but on another PC.
How to properly prepare it so that there are no problems when connecting it to another array, because deleting partitions on this HDD via GParted, as I understand it, is not enough?
And the second question, how to check that the GRUB bootloader is installed on both hdds in raid-1?
Thank you.

Answer 1

sudo dd if=/dev/zero of=/dev/sdТВОЙДИСК bs=1M count=1024

You overwrite the first gigabyte of the disk. Instead of the md-array header and FS pieces, there will be zeros. You can also wipe the entire disk with zeros.

Answer 2

because deleting partitions [...] isn't enough?

- enough, if we are not talking about deleting secret information when transferring the disk to third parties. When synchronizing the array, all the same, the old information on this disk will be overwritten.
A pre-created partition with the =fd type (Linux raid autodetect) is added to the software RAID.

how to check if GRUB bootloader is installed on both hdds

- no need to check, you just need to install it on a new disk. How to install, and how to specify which disk to install on - is easy to google.