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lvreduce

Make a logical volume smaller — with -r the file system is shrunk first (ext4 only; XFS cannot shrink).

Level
RHCSA exam
Group
LVM
Needs root
Yes
Package
lvm2

What it does

Shrinking is risky: if the LV gets smaller than the file system, data is lost. lvreduce -r checks and shrinks the file system before the LV (it may need to unmount it; newer lvm2 asks or does it with --fsmode manage).

XFS file systems cannot be shrunk. To make an XFS volume smaller: back up, recreate smaller, restore.

How to write it

lvreduce (-L [-]SIZE | -l [-]EXTENTS) [-r] [OPTION]... VG/LV

Options 21

Most used

-L, --size [-]SIZE
New size or - removed size, like -1G or 3G.
-l, --extents [-]N[%VG|%LV|%FREE|%ORIGIN]
In extents or percent.
-r, --resizefs
Shrink the file system first (ext4).
-n, --nofsck
Do not check the file system first.
--fs checksize|resize|resize_fsadm|ignore
File system handling (newer lvm2).
--fsmode manage|offline|nochange
May LVM unmount/mount for the resize.
-f, --force
Do not ask (dangerous).
-A, --autobackup y|n
Back up the metadata.
--noudevsync
Do not wait for udev.
--reportformat basic|json
Output format.

Common LVM options

-t, --test
Test only; change nothing.
-v, --verbose
More output (repeat for more).
-q, --quiet
Less output.
-y, --yes
Answer yes to questions.
-d, --debug
Debug output.
--config STRING
Override lvm.conf settings for this command only.
--commandprofile STRING, --profile STRING
Use a configuration profile.
--devices PV, --devicesfile STRING
Limit the devices LVM looks at.
--driverloaded y|n, --nolocking, --lockopt STRING, --nohints, --journal STRING
Special and debug settings.
-h, --help, --longhelp
Show help.
--version
Show the version.

Examples 10

$ run as a normal user# run as root (or with sudo)

  1. 1Shrink an ext4 LV safely

    lvreduce -r -L 3G /dev/vgfiles/lvdocs

    Runs e2fsck and resize2fs, then shrinks the LV.

  2. 2Remove 1 GiB

    lvreduce -r -L -1G /dev/vgfiles/lvdocs

    Relative size.

  3. 3Check the free space first

    df -h /docs

    The data must fit into the new size.

  4. 4Do it by hand (old way)

    umount /docs
e2fsck -f /dev/vgfiles/lvdocs
resize2fs /dev/vgfiles/lvdocs 3G
lvreduce -L 3G /dev/vgfiles/lvdocs
mount /docs

    File system first, then LV — never the other way.

  5. 5Test only

    lvreduce -t -r -L 3G /dev/vgfiles/lvdocs

    Shows what would happen.

  6. 6XFS cannot shrink

    lvreduce -r -L 3G /dev/vgfiles/lvfiles

    Fails for XFS: back up, lvremove, lvcreate smaller, mkfs.xfs, restore.

  7. 7Shrink a swap LV

    swapoff /dev/rhel/swap; lvreduce -L 1G /dev/rhel/swap; mkswap /dev/rhel/swap; swapon -a

    Swap holds no data after swapoff.

  8. 8Free space for another LV

    lvreduce -r -L -2G /dev/vgdata/lvweb; lvcreate -n lvnew -L 2G vgdata

    Move space between LVs in one VG.

  9. 9Verify the data afterwards

    ls /docs; df -h /docs

    Your files are still there.

  10. 10Back up before shrinking

    tar -czf /root/docs-backup.tgz -C /docs .

    Always, on real systems.

Watch out

  • Never lvreduce without -r on an LV with a file system: the end of the file system is cut off.

Exit codes

0Done.
5Error.

Full manual

This page explains the command in simple words. The original manual has every detail.

In your terminal: man 8 lvreduce

Open the man page (linux.die.net)man7.org