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5.4.15. Shrinking Logical Volumes
You can reduce the size of a logical volume with the
Shrinking is not supported on a GFS2 or XFS file system, so you cannot reduce the size of a logical volume that contains a GFS2 or XFS file system.
If the logical volume you are reducing contains a file system, to prevent data loss you must ensure that the file system is not using the space in the logical volume that is being reduced. For this reason, it is recommended that you use the
--resizefsoption of the
lvreducecommand when the logical volume contains a file system. When you use this option, the
lvreducecommand attempts to reduce the file system before shrinking the logical voume. If shrinking the file sytem fails, as can occur if the file system is full or the file system does not support shrinking, then the
lvreducecommand will fail and not attempt to shrink the logical volume.
In most cases, the
lvreducecommand warns about possible data loss and asks for a confirmation. However, you should not rely on these confirmation prompts to prevent data loss because in some cases you will not see these prompts, such as when the logical volume is inactive or the
--resizefsoption is not used.
Note that using the
--testoption of the
lvreducecommand does not indicate where the operation is safe, as this option does not check the file system or test the file system resize.
The following command shrinks the logical volume
lvol1in volume group
vg00to be 64 megabytes. In this example,
lvol1contains a file system, which this command resizes together with the logical volume. This example shows the output to the command.
lvreduce --resizefs -L 64M vg00/lvol1fsck from util-linux 2.23.2 /dev/mapper/vg00-lvol1: clean, 11/25688 files, 8896/102400 blocks resize2fs 1.42.9 (28-Dec-2013) Resizing the filesystem on /dev/mapper/vg00-lvol1 to 65536 (1k) blocks. The filesystem on /dev/mapper/vg00-lvol1 is now 65536 blocks long. Size of logical volume vg00/lvol1 changed from 100.00 MiB (25 extents) to 64.00 MiB (16 extents). Logical volume vg00/lvol1 successfully resized.
Specifying the - sign before the resize value indicates that the value will be subtracted from the logical volume's actual size. The following example shows the command you would use if, instead of shrinking a logical volume to an absolute size of 64 megabytes, you wanted to shrink the volume by a value 64 megabytes.
lvreduce --resizefs -L -64M vg00/lvol1