MAN page from StartCom 5 device-mapper-1.02.67-2.SEL5_6.x86_64.rpm

DMSETUP

Section: MAINTENANCE 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][{ --addnodeonresume | --addnodeoncreate }]
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 renamedevice_name --setuuid uuid
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] [--showkeys][device_name]
dmsetup waitdevice_name[event_nr]
dmsetup mknodes[device_name]
dmsetup udevcreatecookie
dmsetup udevreleasecookie[cookie]
dmsetup udevflagscookie
dmsetup udevcompletecookie
dmsetup udevcomplete_all[age_in_minutes]
dmsetup udevcookies
dmsetup targets
dmsetup version
dmsetup setgeometrydevice_name cyl head sect start
dmsetup splitnamedevice_name[subsystem]

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

--checks: Perform additional checks on the operations requested and reportpotential problems. Useful when debugging scripts.In some cases these checks may slow down operations noticeably.
-c|-C|--columns: Display output in columns rather than as Field: Value lines.
-h|--help: Outputs a summary of the commands available, optionally includingthe list of report fields (synonym with help command).
--inactive: When returning any table information from the kernel report on the inactive table instead of the live table.Requires kernel driver version 4.16.0 or above.
-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.
--addnodeonresume: Ensure /dev/mapper node exists after dmsetup resume (default with udev).
--addnodeoncreate: Ensure /dev/mapper node exists after dmsetup create.
--udevcookie cookie: Use cookie for udev synchronisation.
--noudevrules: Do not allow udev to manage nodes for devices in device-mapper directory.
--noudevsync: Do not synchronise with udev when creating, renaming or removing devices.
-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.
-y|--yes: Answer yes to all prompts automatically.
-v|--verbose [-v|--verbose]: Produce additional output.
--verifyudev: If udev synchronisation is enabled, verify that udev operations get performedcorrectly and try to fix up the device nodes afterwards if not.
--version: Display the library and kernel driver version.

COMMANDS

clear: device_name
Destroys the table in the inactive table slot for device_name.
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: -c|-C|--columns[--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 processes 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.
rename: device_name --setuuid uuid
Sets the uuid of a device that was created without a uuid.After a uuid has been set it cannot be changed.
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.
splitname: device_name[subsystem]
Splits given device name into subsystem constituents.Default subsystem is LVM.
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] [--showkeys][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.Encryption keys are suppressed in the table output for the crypttarget unless the --showkeys parameter is supplied.
targets: Displays the names and versions of the currently-loaded targets.
udevcreatecookie: Creates a new cookie to synchronize actions with udev processing.The output is a cookie value. Normally we don't need to create cookies sincedmsetup creates and destroys them for each action automatically. However, we cangenerate one explicitly to group several actions together and use only onecookie instead. We can define a cookie to use for each relevant command by using--udevcookie option. Alternatively, we can export this value into the environmentof the dmsetup process as DM_UDEV_COOKIE variable and it will be used automaticallywith all subsequent commands until it is unset.Invoking this command will create system-wide semaphore that needs to be cleanedup explicitly by calling udevreleasecookie command.
udevreleasecookie: [cookie]
Waits for all pending udev processing bound to given cookie value and clean upthe cookie with underlying semaphore. If the cookie is not given directly,the command will try to use a value defined by DM_UDEV_COOKIE environment variable.
udevflags: cookie
Parses given cookie value and extracts any udev control flags encoded.The output is in environment key format that is suitable for use in udevrules. If the flag has its symbolic name assigned then the output isDM_UDEV_FLAG_<flag_name>='1', DM_UDEV_FLAG<flag_position>='1' otherwise.Subsystem udev flags don't have symbolic names assigned and these ones arealways reported as DM_SUBSYSTEM_UDEV_FLAG<flag_position>='1'. There are16 udev flags altogether.
udevcomplete: cookie
Wake any processes that are waiting for udev to complete processing the specified cookie.
udevcomplete_all: Remove all cookies older than the specified number of minutes. Any process waiting on a cookie will be resumed immediately.
udevcookies: List all existing cookies. Cookies are system-wide semaphores with keysprefixed by two predefined bytes (0x0D4D).
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.
DM_UDEV_COOKIE: A cookie to use for all relevant commands to synchronize with udev processing.It is an alternative to using --udevcookie option.

AUTHORS

Original version: Joe Thornber (thornberAATTsistina.com)

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