vgscan scans all SCSI, (E)IDE disks, multiple devices and a bunch
of other disk devices in the system looking for LVM physical volumes
and volume groups. Define a filter in lvm.conf(5) to restrict
the scan to avoid a CD ROM, for example.
In LVM2, vgscans take place automatically; but you might still need to
run one explicitly after changing hardware.
See lvm for common options.
Also checks the LVM special files in /dev that are needed for active
logical volumes and creates any missing ones and removes unused ones.