Red Hat Enterprise Linux 5 Administration Unleashed

172CHAPTER 7Managing Storagephysical volume100GBphysical volume100GBphysical volume100GB/boot100MB (ext3)logical volume grouplogical volume/homelogical volume/logical volume/tmpFREE SPACEFIGURE 7.1How Logical Volume Manager WorksLVM is used by default during installation for all mount points except the /boot partition,which cannot exist on a logical volume. This section discusses how to perform LVM operationsafter installation such as creating a physical volume for a newly added hard drive,expanding logical volumes, and generating LV snapshots.Table 7.1 summaries the LVM tools available after installation.TABLE 7.1 LVM ToolsLVM Tool Descriptionpvcreate Create physical volume from a hard drivevgcreate Create logical volume group from one or more physical volumesvgextend Add a physical volume to an existing volume groupvgreduce Remove a physical volume from a volume grouplvcreate Create a logical volume from available space in the volume grouplvextend Extend the size of a logical volume from free physical extents in the logicalvolume grouplvremove Remove a logical volume from a logical volume group, after unmounting itvgdisplay Show properties of existing volume grouplvdisplay Show properties of existing logical volumespvscan Show properties of existing physical volumesAdding Additional Disk SpaceOne big advantage of using LVM is that the size of a logical volume can be increased andlogical volumes can be added to create additional mount points. To modify the LVMconfiguration post-installation, the lvm2 package needs to be installed. Refer to Chapter 3,“Operating System Updates,” for details on installing packages.TIPIf possible, leave free disk space when partitioning during installation so logicalvolume sizes can be increased without adding additional hard drives.