What does `mdadm --manage /dev/md1` do? Do I need to "undo" it?

Question

I ran this hoping to find out a bit about my array (I now know I should have used --detail). But I'm not clear what the --manage option does. It gave no output, and just put me back to the bash prompt.

Do I need to run some command to undo whatever that did?

Answer 1

mdadm --manage /dev/md1 does nothing.

The --manage option selects Manage mode (which is the default mode anyway), and the argument /dev/md1 selects the RAID device to manage. The action to perform would come next, but you gave none, so none is performed.