Need to move RAID1 with mounted partition

[Leslie Rhorer <lesrhorer@xxxxxxx>]

Hello all,

	I have run into a little problem.  I know of a couple of ways to fix it 
by shutting down the system and physically taking it apart, but for 
various reasons I don't wish to take that route.  I want to be able to 
re-arrange the system with it running.

	The latest version (bullseye) of Debian will not complete its upgrade 
properly because my /boot file system is a little too small.  I have two 
bootable drives with three partitions on them.  The first partition on 
each drive is assembled into a RAID1 as /dev/md1 mounted as /boot.  Once 
the system is booted, these can of course easily be umounted, the RAID1 
stopped, and there is then no problem increasing the size of the 
partitions if there were space to be had.  The third partition on each 
drive is assigned as swap, and of course it was easy to resize those 
partitions, leaving an additional 512MB between the second and third 
partitions on each drive.  All I need to do is move the second partition 
on each drive up by 512MB.

	The problem is the second partition on both drives is also assembled 
into a RAID1 array on /dev/md2, formatted as ext4 and mounted as /.  Is 
there a way I can move the RAID1 array up without shutting down the 
system?  I don't need to resize the array, just move it.  Is there a way 
to umount the root without halting the system?  Note the system is 
headless, so access is via ssh over the network.