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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.
Note
If you are creating or modifying an LVM volume for a clustered environment, you must ensure that you are running the
clvmd
daemon. For information, see see Section 3.1, “Creating LVM Volumes in a Cluster”.
4.1. Using CLI Commands 复制链接链接已复制到粘贴板!
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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
--units
argument 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
lvol0
in a volume group called vg0
can 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 vg0
command will display all the logical volumes in volume group vg0
.
All LVM commands accept a
-v
argument, which can be entered multiple times to increase the output verbosity. For example, the following examples shows the default output of the lvcreate
command.
lvcreate -L 50MB new_vg
# lvcreate -L 50MB new_vg
Rounding up size to full physical extent 52.00 MB
Logical volume "lvol0" created
The following command shows the output of the
lvcreate
command with the -v
argument.
You could also have used the
-vv
, -vvv
or the -vvvv
argument to display increasingly more details about the command execution. The -vvvv
argument provides the maximum amount of information at this time. The following example shows only the first few lines of output for the lvcreate
command with the -vvvv
argument specified.
You can display help for any of the LVM CLI commands with the
--help
argument of the command.
commandname --help
commandname --help
To display the man page for a command, execute the
man
command:
man commandname
man commandname
The
man lvm
command 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/sdf
which 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 see Section 6.4, “Recovering Physical Volume Metadata”.