$ Linux Command

Disk

lvreduce

Reduce the size of an LVM logical volume.

lvmlogical-volumereduceshrinkdisk

Additional Notes

lvreduce shrinks an existing LVM logical volume. Unlike extending, reducing a logical volume is a destructive operation that requires careful preparation: the filesystem must be shrunk first, then the logical volume can be reduced to match.

The filesystem must be unmounted (or at least remounted read-only) for most filesystem types. XFS does not support shrinking at all, making lvreduce unsuitable for XFS volumes. ext4 can be shrunk but only when unmounted.

Syntax

lvreduce [options] logical-volume-path

Parameters

  • logical-volume-path: Path to the logical volume to reduce (e.g., /dev/vgname/lvname).

Common Options

  • -L size, --size size: New total size (e.g., -L 5G) or reduction amount (-L -3G).
  • -l extents, --extents extents: Size in physical extents, or reduction in extents.
  • -r, --resizefs: Resize the filesystem before shrinking the LV.
  • -f, --force: Force reduction without safety checks (use with extreme caution).
  • -n, --nofsck: Do not run filesystem check before shrinking.

Examples

lvreduce -L -3G /dev/myvg/volume

Reduce the logical volume by 3 GB.

lvreduce -L 5G /dev/myvg/volume

Set the logical volume to exactly 5 GB.

lvreduce -r -L -2G /dev/myvg/volume

Resize the filesystem and reduce the logical volume in one step.

Safe Reduction Steps (Manual)

umount /dev/myvg/volume
e2fsck -f /dev/myvg/volume
resize2fs /dev/myvg/volume 10G
lvreduce -L 10G /dev/myvg/volume
mount /dev/myvg/volume /mnt

The safe manual approach: unmount, check, shrink filesystem, shrink LV, remount.

Practical Notes

  • Always back up critical data before shrinking a logical volume.
  • Reduce the filesystem before reducing the logical volume to avoid data corruption.
  • XFS filesystems cannot be shrunk. For XFS, you must back up, recreate the volume, and restore.
  • The -r flag handles the resize in the correct order but should still be used with caution.