Advanced storage

LVM from Part II gave you logical volumes instead of fixed partitions. Now let us see what that buys you in practice: grow a volume without unmounting the filesystem, and take a snapshot before a risky operation. After that come disk mirroring with mdadm, swap, and filesystem repair.

The key rule of this chapter: first the volume grows, then the filesystem inside it. These are two separate layers, and each one grows with its own command.

Say the group datavg has free space and the volume files is running short. First hand the volume another 10 gigabytes:

$ sudo lvextend -L +10G /dev/datavg/files   # +10G on top of the current size

The volume is bigger now, but the filesystem inside still thinks it is the old size. You ha