MAN page from StartCom 5 device-mapper-1.02.24-1.ML5.x86_64.rpm

DMSETUP

Section: MAINTENTANCE COMMANDS (8)
Updated: Apr 06 2006
Index

NAME

dmsetup - low level logical volume management

SYNOPSIS

dmsetup help[-c|-C|--columns]
dmsetup create device_name [-u uuid] [--notable | --table <table> | table_file]
dmsetup remove[-f|--force] device_name
dmsetup remove_all[-f|--force]
dmsetup suspend[--nolockfs] [--noflush] device_name
dmsetup resumedevice_name
dmsetup loaddevice_name [--table <table> | table_file]
dmsetup cleardevice_name
dmsetup reloaddevice_name [--table <table> | table_file]
dmsetup renamedevice_name new_name
dmsetup messagedevice_name sector message
dmsetup ls[--target target_type] [--exec command] [--tree [-o options]]
dmsetup info [device_name]
dmsetup info -c|-C|--columns[--noheadings] [--separator separator] [-o fields] [-O|--sort sort_fields][device_name]
dmsetup deps[device_name]
dmsetup status[--target target_type][device_name]
dmsetup table[--target target_type][device_name]
dmsetup waitdevice_name[event_nr]
dmsetup mknodes[device_name]
dmsetup targets
dmsetup version
dmsetup setgeometrydevice_name cyl head sect start

devmap_namemajor minor
devmap_name major:minor

DESCRIPTION

dmsetup manages logical devices that use the device-mapper driver. Devices are created by loading a table that specifies a target foreach sector (512 bytes) in the logical device.

The first argument to dmsetup is a command. The second argument is the logical device name or uuid.

Invoking the command as devmap_name is equivalent to
dmsetup info -c --noheadings -j major -m minor.

OPTIONS

-c|-C|--columns: Display output in columns rather than as Field: Value lines.
-j|--major major: Specify the major number.
-m|--minor minor: Specify the minor number.
-n|--noheadings: Suppress the headings line when using columnar output.
--noopencount: Tell the kernel not to supply the open reference count for the device.
--notable: When creating a device, don't load any table.
-o|--options: Specify which fields to display.
-r|--readonly: Set the table being loaded read-only.
--readahead [+]<sectors>|auto|none: Specify read ahead size in units of sectors.The default value is "auto" which allows the kernel to choosea suitable value automatically. The + prefix lets youspecify a minimum value which will not be used if it issmaller than the value chosen by the kernel."None" is equivalent to specifying zero.
--table <table>: Specify a one-line table directly on the command line.
-u|--uuid: Specify the uuid.
-v|--verbose [-v|--verbose]: Produce additional output.
--version: Display the library and kernel driver version.

COMMANDS

create: device_name [-u uuid] [--notable | --table <table> | table_file]
Creates a device with the given name.If table_file or <table> is supplied, the table is loaded and made live.Otherwise a table is read from standard input unless --notable is used.The optional uuid can be used in place ofdevice_name in subsequent dmsetup commands. If successful a device will appear as/dev/device-mapper/<device-name>. See below for information on the table format.
deps: [device_name]
Outputs a list of (major, minor) pairs for devices referenced by thelive table for the specified device.
help: [-c|-C|--columns]
Outputs a summary of the commands available, optionally includingthe list of report fields.
info: [device_name]
Outputs some brief information about the device in the form:

    State: SUSPENDED|ACTIVE, READ-ONLY

    Tables present: LIVE and/or INACTIVE

    Open reference count

    Last event sequence number (used by wait)

    Major and minor device number

    Number of targets in the live table

    UUID
info: [--noheadings] [--separator separator] [-o fields] [-O|--sort sort_fields][device_name]
Output you can customise.Fields are comma-separated and chosen from the following list:name, major, minor, attr, open, segments, events, uuid.Attributes are: (L)ive, (I)nactive, (s)uspended, (r)ead-only, read-(w)rite.Precede the list with '+' to appendto the default selection of columns instead of replacing it.Precede any sort_field with - for a reverse sort on that column.
ls: [--target target_type][--exec command][--tree [-o options]]
List device names. Optionally only list devices that have at leastone target of the specified type. Optionally execute a command foreach device. The device name is appended to the supplied command.--tree displays dependencies between devices as a tree.It accepts a comma-separate list of options.Some specify the information displayed against each node:device/nodevice; active, open, rw, uuid.Others specify how the tree is displayed:ascii, utf, vt100; compact, inverted, notrunc.
load|reload: device_name [--table <table> | table_file]
Loads <table> or table_file into the inactive table slot for device_name.If neither is supplied, reads a table from standard input.
message: device_name sector message
Send message to target. If sector not needed use 0.
mknodes: [device_name]
Ensure that the node in /dev/mapper for device_name is correct.If no device_name is supplied, ensure that all nodes in /dev/mapper correspond to mapped devices currently loaded by the device-mapper kerneldriver, adding, changing or removing nodes as necessary.
remove: [-f|--force] device_name
Removes a device. It will no longer be visible to dmsetup.Open devices cannot be removed except with older kernelsthat contain a version of device-mapper prior to 4.8.0.In this case the device will be deleted when its open_count drops to zero. From version 4.8.0 onwards, if a device can'tbe removed because an uninterruptible process is waiting forI/O to return from it, adding --force will replace the table with one that fails all I/O, which might allow the process to be killed.
remove_all: [-f|--force]
Attempts to remove all device definitions i.e. reset the driver.Use with care! From version 4.8.0 onwards, if devices can'tbe removed because uninterruptible processess are waiting forI/O to return from them, adding --force will replace the table with one that fails all I/O, which might allow the process to be killed. This also runs mknodes afterwards.
rename: device_name new_name
Renames a device.
resume: device_name
Un-suspends a device. If an inactive table has been loaded, it becomes live.Postponed I/O then gets re-queued for processing.
setgeometry: device_name cyl head sect start
Sets the device geometry to C/H/S.
status: [--target target_type][device_name]
Outputs status information for each of the device's targets.With --target, only information relating to the specified target typeis displayed.
suspend: [--nolockfs] [--noflush]device_name
Suspends a device. Any I/O that has already been mapped by the devicebut has not yet completed will be flushed. Any further I/O to thatdevice will be postponed for as long as the device is suspended.If there's a filesystem on the device which supports the operation, an attempt will be made to sync it first unless --nolockfs is specified.Some targets such as recent (October 2006) versions of multipath may supportthe --noflush option. This lets outstanding I/O that has not yet reached thedevice to remain unflushed.
table: [--target target_type][device_name]
Outputs the current table for the device in a format that can be fedback in using the create or load commands.With --target, only information relating to the specified target typeis displayed.
targets: Displays the names and versions of the currently-loaded targets.
version: Outputs version information.
wait: device_name[event_nr]
Sleeps until the event counter for device_name exceeds event_nr.Use -v to see the event number returned.To wait until the next event is triggered, use info to findthe last event number.

TABLE FORMAT

Each line of the table specifies a single target and is of the form:

logical_start_sector num_sectors target_type target_args

There are currently three simple target types available together with more complex optional ones that implement snapshots and mirrors.

linear: destination_device start_sector
The traditional linear mapping.
striped: num_stripes chunk_size [destination start_sector]+
Creates a striped area.
e.g. striped 2 32 /dev/hda1 0 /dev/hdb1 0will map the first chunk (16k) as follows:

    LV chunk 1 -> hda1, chunk 1

    LV chunk 2 -> hdb1, chunk 1

    LV chunk 3 -> hda1, chunk 2

    LV chunk 4 -> hdb1, chunk 2

    etc.
error: Errors any I/O that goes to this area. Useful for testing orfor creating devices with holes in them.

EXAMPLES

# A table to join two disks together

0 1028160 linear /dev/hda 0
1028160 3903762 linear /dev/hdb 0

# A table to stripe across the two disks,
# and add the spare space from
# hdb to the back of the volume

0 2056320 striped 2 32 /dev/hda 0 /dev/hdb 0
2056320 2875602 linear /dev/hdb 1028160

ENVIRONMENT VARIABLES

DM_DEV_DIR: The device directory name.Defaults to "/dev" and must be an absolute path.

AUTHORS

Original version: Joe Thornber (thornberAATTsistina.com)

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