Chapter 4. LVM Administration with CLI Commands
This chapter summarizes the individual administrative tasks you can perform with the LVM Command Line Interface (CLI) commands to create and maintain logical volumes.
In addition to the LVM Command Line Interface (CLI), you can use System Storage Manager (SSM) to configure LVM logical volumes. For information on using SSM with LVM, see the Storage Administration Guide.
4.1. Using CLI Commands
There are several general features of all LVM CLI commands.
When sizes are required in a command line argument, units can always be specified explicitly. If you do not specify a unit, then a default is assumed, usually KB or MB. LVM CLI commands do not accept fractions.
When specifying units in a command line argument, LVM is case-insensitive; specifying M or m is equivalent, for example, and powers of 2 (multiples of 1024) are used. However, when specifying the
--unitsargument in a command, lower-case indicates that units are in multiples of 1024 while upper-case indicates that units are in multiples of 1000.
Where commands take volume group or logical volume names as arguments, the full path name is optional. A logical volume called
lvol0in a volume group called
vg0can be specified as
vg0/lvol0. Where a list of volume groups is required but is left empty, a list of all volume groups will be substituted. Where a list of logical volumes is required but a volume group is given, a list of all the logical volumes in that volume group will be substituted. For example, the
lvdisplay vg0command will display all the logical volumes in volume group
All LVM commands accept a
-vargument, which can be entered multiple times to increase the output verbosity. For example, the following examples shows the default output of the
lvcreate -L 50MB new_vgRounding up size to full physical extent 52.00 MB Logical volume "lvol0" created
The following command shows the output of the
lvcreatecommand with the
lvcreate -v -L 50MB new_vgFinding volume group "new_vg" Rounding up size to full physical extent 52.00 MB Archiving volume group "new_vg" metadata (seqno 4). Creating logical volume lvol0 Creating volume group backup "/etc/lvm/backup/new_vg" (seqno 5). Found volume group "new_vg" Creating new_vg-lvol0 Loading new_vg-lvol0 table Resuming new_vg-lvol0 (253:2) Clearing start of logical volume "lvol0" Creating volume group backup "/etc/lvm/backup/new_vg" (seqno 5). Logical volume "lvol0" created
You could also have used the
-vvvvargument to display increasingly more details about the command execution. The
-vvvvargument provides the maximum amount of information at this time. The following example shows only the first few lines of output for the
lvcreatecommand with the
lvcreate -vvvv -L 50MB new_vg#lvmcmdline.c:913 Processing: lvcreate -vvvv -L 50MB new_vg #lvmcmdline.c:916 O_DIRECT will be used #config/config.c:864 Setting global/locking_type to 1 #locking/locking.c:138 File-based locking selected. #config/config.c:841 Setting global/locking_dir to /var/lock/lvm #activate/activate.c:358 Getting target version for linear #ioctl/libdm-iface.c:1569 dm version OF  #ioctl/libdm-iface.c:1569 dm versions OF  #activate/activate.c:358 Getting target version for striped #ioctl/libdm-iface.c:1569 dm versions OF  #config/config.c:864 Setting activation/mirror_region_size to 512 ...
You can display help for any of the LVM CLI commands with the
--helpargument of the command.
To display the man page for a command, execute the
man lvmcommand provides general online information about LVM.
All LVM objects are referenced internally by a UUID, which is assigned when you create the object. This can be useful in a situation where you remove a physical volume called
/dev/sdfwhich is part of a volume group and, when you plug it back in, you find that it is now
/dev/sdk. LVM will still find the physical volume because it identifies the physical volume by its UUID and not its device name. For information on specifying the UUID of a physical volume when creating a physical volume, see Section 6.3, “Recovering Physical Volume Metadata”.