[kwlug-disc] Growing (live file systems)

[Charles M]

I've set up a server with 2 x 3TB drives in a RAID1 configuration. I
installed Ubuntu Server 20.04 on the system and MegaRAID's storcli
program. I then added 2 more 3TB drives and used storcli to grow the
RAID1 to 6TB. On reboot Ubuntu server still loads up, however it
thinks it's on 3TB because the OS hasn't been expanded to the size of
the RAID array.

This thread on askubuntu seems to imply that it's possible to expand
the operating system without taking it down:

https://askubuntu.com/questions/24027/how-can-i-resize-an-ext-root-partition-at-runtime

My understanding from this thread is that we would:
1. use fdisk to resize the partition first - taking note to start the
partition in the same block as the old one.
2. use resize2fs to increase the size of the partition

One thing I didn't see mentioned is whether grub would recognize these
changes? Wouldn't grub-install also need to be run after this?

Thanks to all you server and drive gurus!

Charles