LVM
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pv: physical device (e.g. /dev/md0 or /dev/sda1)
vg: volume group (consists of 1 or more pvs, contains lvs); has a name (e.g. lvm)
lv: logical volume (has a name which defines its path, e.g. /dev/lvm/root which equals dev/mapper/lvm-root)
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pvcreate /dev/md0	initializes /dev/md0 as phys device for a volume group
vgcreate lvm /dev/md0	create volume group lvm with phys device /dev/md0
lvcreate -L30G -nroot lvm ; mkfs.ext4 /dev/lvm/root	create logical volume root, sized 30G in volume group lvm; format with ext4
lvextend -L60G -nroot lvm ; resize2fs /dev/lvm/root	extend /dev/lvm/root to 60G; also resize file system to new size

pvs, vgs, lvs	show short info about pv, vg and lv

pvdisplay, vgdisplay, lvdisplay	show long info

pvscan /dev/md0	scan disks for physical volumes (e.g. when running live system)
vgextend lvm /dev/md1	add phys device /dev/md1 to volume group lvm (need pvcreate first!)
pvmove /dev/md0 ; vgreduce lvm /dev/md0	move all logical volumes from /dev/md0 and remove phys device from volume group