I’m planning to install a new hard drive to expand the root logical volume on my machine, which is having now pretty continual capacity issues. The various tutorials for RHEL-like operating systems seem straightforward enough, but there seems to be some disagreement as to whether or not if you’re expanding the root LV you need to unmount it first (and thus would need to boot the machine from a USB drive or the like in rescue mode).

Does anyone know if this is necessary?


If you're using LVM then there's no need to unmount any volume before expanding it except in a very few corner cases. Simply attempt to extend the LV, and if you need to perform the operation offline you will be told at that point.


You don't need to unmount the root lv if it is a type that supports online resizing (online regrowing). I've done this with EXT4 partitions quite often.

SHRINKING a lv usually (always?) needs to be done with the partition unmounted.

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