lvreduce(1M)

NAME

lvreduce — decrease space allocation or the number of mirror copies of logical volumes

SYNOPSIS

/usr/sbin/lvreduce [-A autobackup] [-f] -l le_number lv_path

/usr/sbin/lvreduce [-A autobackup] [-f] -L lv_size lv_path

/usr/sbin/lvreduce [-A autobackup] -m mirror_copies lv_path [pv_path ...]

/usr/sbin/lvreduce [-A autobackup] -k -m mirror_copies lv_path

Remarks

Mirrored disk operations require the installation of the optional HP MirrorDisk/UX software, which is not included in the standard HP-UX operating system.

lvreduce cannot be performed if the volume group is activated in shared mode.

DESCRIPTION

The lvreduce command reduces the number of logical extents allocated to a logical volume specified by lv_path. The excess physical extents in the logical volume and any mirror copies are deallocated.

Alternatively, it reduces the number of mirror copies in the logical volume. The physical extents that comprise the deleted mirror copy or copies are deallocated. If pv_path ... is specified, the mirror or mirrors to be removed will be deallocated from those specific physical volumes.

lvreduce asks for confirmation before deallocating logical extents if the -f option is omitted.

Options and Arguments

The -m option and pv_path argument are only meaningful if the optional HP MirrorDisk/UX software has been installed on the system.

lvreduce recognizes the following options and arguments:

lv_path

The block device path name of a logical volume.

pv_path

The block device path name of a physical volume.

-A autobackup

Set automatic backup for invocation of this command. autobackup can have one of the following values:

y

Automatically back up configuration changes made to the logical volume. This is the default.

After this command executes, the vgcfgbackup command (see vgcfgbackup(1M)) is executed for the volume group to which the logical volume belongs.

n

Do not back up configuration changes.

-f

Force reduction of the number of logical extents without first requesting confirmation.

This option can be dangerous when there is a file system on the lv_path that is larger than the size that the logical volume is being reduced to. If the file system is unmounted, the -f option forces the reduction of the logical volume without reducing the file system. The file system becomes corrupt and is not mountable. If the file system is mounted, lvreduce fails, preventing a mounted file system from becoming corrupted.

-l le_number

Decrease the space allocated to the logical volume, specified in logical extents. le_number is a decimal value smaller than the current number of logical extents, in the range 1 to 65535 (the implementation limit).

One, and only one, -l, -L, or -m option must be supplied.

-L lv_size

Decrease the space allocated to the logical volume, specified in megabytes. lv_size is a decimal value smaller than the current logical volume size, in the range 1 to 16777216 (the implementation limit). lv_size is rounded up to the nearest multiple of the logical extent size, equivalent to the physical extent size defined for the volume group by the vgcreate command (see vgcreate(1M)).

One, and only one, -l, -L, or -m option must be specified.

-m mirror_copies

Reduce the number of mirror copies allocated for each logical extent. A mirror copy contains the same data as the original. mirror_copies can have the value 0 or 1. It must be smaller than the current value.

If optional pv_path arguments are specified, the mirror copies are deallocated from the specified physical volumes.

One, and only one, -l, -L, or -m option must be specified.

-k

This option should be used only in the special instance when you want to reduce a mirrored logical volume on a physical volume that is missing or has failed.

Use this option with the -m option.

EXTERNAL INFLUENCES

Environment Variables

LANG determines the language in which messages are displayed.

If LANG is not specified or is null, it defaults to "C" (see lang(5)).

If any internationalization variable contains an invalid setting, all internationalization variables default to "C" (see environ(5)).

EXAMPLES

Decrease the number of the logical extents of a logical volume to one hundred:

lvreduce -l 100 /dev/vg01/lvol3 

Reduce to one mirror (that is, an original and one copy) for each logical extent of a logical volume:

lvreduce -m 1 /dev/vg01/lvol5 

Remove mirror copies of logical extents of a logical volume from the physical volume /dev/dsk/c1t0d0:

lvreduce -m 0 /dev/vg01/lvol4 /dev/dsk/c1t0d0 

Remove a logical volume from a one-way mirrored set on the specified pv_path.

lvreduce -m 0 -k /dev/vg01/lvol1 /dev/dsk/c1t0d0 

WARNINGS

LVM does not store any information about which physical extents within a logical volume contain useful data; therefore, reducing the space allocated to a logical volume without doing a prior backup of the data could lead to the loss of useful data. The lvreduce command on a logical volume containing a file system of greater length than the size being reduced to will cause data corruption.

To reduce a logical volume being used for swap, that swap area must not be currently in use.