x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
DMSETUP(8) MAINTENANCE COMMANDS DMSETUP(8)
NAME
dmsetup - low level logical volume management
SYNOPSIS
dmsetup clear device_name
dmsetup create device_name [-u uuid] [--notable|--table <table>|
table_file] [{--addnodeoncreate|--addnodeonresume}] [--readahead
[+]<sectors>|auto|none]
dmsetup deps [-o options] [device_name]
dmsetup help [-c|-C|--columns]
dmsetup info [device_name]
dmsetup info -c|-C|--columns [--noheadings] [--separator separator]
[-o fields] [-O|--sort sort_fields] [device_name]
dmsetup export [device_name]
dmsetup load device_name [--table <table>|table_file]
dmsetup ls [--target target_type] [--exec command] [--tree] [-o
options]
dmsetup message device_name sector message
dmsetup mknodes [device_name]
dmsetup mangle [device_name]
dmsetup reload device_name [--table <table>|table_file]
dmsetup wipe_table device_name
dmsetup remove [-f|--force] [--retry] device_name
dmsetup remove_all [-f|--force]
dmsetup rename device_name new_name
dmsetup rename device_name --setuuid uuid
dmsetup resume device_name [{--addnodeoncreate|--addnodeonresume}]
[--readahead [+]<sectors>|auto|none]
dmsetup setgeometry device_name cyl head sect start
dmsetup splitname device_name [subsystem]
dmsetup status [--target target_type] [--noflush] [device_name]
dmsetup suspend [--nolockfs] [--noflush] device_name
dmsetup table [--target target_type] [--showkeys] [device_name]
dmsetup targets
dmsetup udevcomplete cookie
dmsetup udevcomplete_all [age_in_minutes]
dmsetup udevcookies
dmsetup udevcreatecookie
dmsetup udevflags cookie
dmsetup udevreleasecookie [cookie]
dmsetup version
dmsetup wait [--noflush] device_name [event_nr]
devmap_name major 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 for each
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
--addnodeoncreate
Ensure /dev/mapper node exists after dmsetup create.
--addnodeonresume
Ensure /dev/mapper node exists after dmsetup resume (default
with udev).
--checks
Perform additional checks on the operations requested and report
potential 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 includ-
ing the 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.
--manglename <mangling_mode>
Mangle any character not on a whitelist using mangling_mode when
processing device-mapper device names and UUIDs. The names and
UUIDs are mangled on input and unmangled on output where the
mangling_mode is one of: none (no mangling), hex (always do the
mangling) and auto (only do the mangling if not mangled yet, do
nothing if already mangled, error on mixed; this is used by
default). Character whitelist: 0-9, A-Z, a-z, #+-.:=@_. This
whitelist is also supported by udev. Any character not on a
whitelist is replaced with its hex value (two digits) prefixed
by \x.
-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.
--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.
--readahead [+]<sectors>|auto|none
Specify read ahead size in units of sectors. The default value
is auto which allows the kernel to choose a suitable value auto-
matically. The + prefix lets you specify a minimum value which
will not be used if it is smaller than the value chosen by the
kernel. The value none is equivalent to specifying zero.
-r|--readonly
Set the table being loaded read-only.
--table <table>
Specify a one-line table directly on the command line.
--udevcookie cookie
Use cookie for udev synchronisation.
-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 performed correctly 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]
[{--addnodeoncreate|--addnodeonresume}] [--readahead [+]<sec-
tors>|auto|none]
Creates a device with the given name. If table_file or <table>
is supplied, the table is loaded and made live. Otherwise a ta-
ble is read from standard input unless --notable is used. The
optional uuid can be used in place of device_name in subsequent
dmsetup commands. If successful a device will appear as
/dev/mapper/<device-name>. See below for information on the ta-
ble format.
export [device_name]
Outputs information in key/value format to be imported by other
programs.
deps [-o options] [device_name]
Outputs a list of devices referenced by the live table for the
specified device. Device names on output can be customised by
following options: devno (major and minor pair, used by
default), blkdevname (block device name), devname (map name for
device-mapper devices, equal to blkdevname otherwise).
help [-c|-C|--columns]
Outputs a summary of the commands available, optionally includ-
ing the 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, seg-
ments, events, uuid. Attributes are: (L)ive, (I)nactive,
(s)uspended, (r)ead-only, read-(w)rite. Precede the list with
'+' to append to 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
least one target of the specified type. Optionally execute a
command for each device. The device name is appended to the
supplied command. Device names on output can be customised by
following options: devno (major and minor pair, used by
default), blkdevname (block device name), devname (map name for
device-mapper devices, equal to blkdevname otherwise). --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; blkdevname;
active, open, rw, uuid. Others specify how the tree is dis-
played: 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 stan-
dard input.
wipe_table device_name
Wait for any I/O in-flight through the device to complete, then
replace the table with a new table that fails any new I/O sent
to the device. If successful, this should release any devices
held open by the device's table(s).
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 kernel driver, adding, changing or removing nodes
as necessary.
mangle [device_name]
Ensure existing device-mapper device name and UUID is in the
correct mangled form containing only whitelisted characters
(supported by udev) and do a rename if necessary. Any character
not on the whitelist will be mangled based on the --manglename
setting. Automatic rename works only for device names and not
for device UUIDs because the kernel does not allow changing the
UUID of active devices. Any incorrect UUIDs are reported only
and they must be manually corrected by deactivating the device
first and then reactivating it with proper mangling mode used
(see also --manglename).
remove [-f|--force] [--retry] device_name
Removes a device. It will no longer be visible to dmsetup.
Open devices cannot be removed except with older kernels that
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't be removed because
an uninterruptible process is waiting for I/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. If an attempt
to remove a device fails, perhaps because a process run from a
quick udev rule temporarily opened the device, the --retry
option will cause the operation to be retried for a few seconds
before failing.
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't be
removed because uninterruptible processes are waiting for I/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 [{--addnodeoncreate|--addnodeonresume}] [--readahead
[+]<sectors>|auto|none]
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] [--noflush] [device_name]
Outputs status information for each of the device's targets.
With --target, only information relating to the specified target
type any is displayed. With --noflush, the thin target (from
version 1.3.0) doesn't commit any outstanding changes to disk
before reporting its statistics.
suspend [--nolockfs] [--noflush] device_name
Suspends a device. Any I/O that has already been mapped by the
device but has not yet completed will be flushed. Any further
I/O to that device will be postponed for as long as the device
is suspended. If there's a filesystem on the device which sup-
ports 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 support the --noflush
option. This lets outstanding I/O that has not yet reached the
device to remain unflushed.
table [--target target_type] [--showkeys] [device_name]
Outputs the current table for the device in a format that can be
fed back in using the create or load commands. With --target,
only information relating to the specified target type is dis-
played. Encryption keys are suppressed in the table output for
the crypt target unless the --showkeys parameter is supplied.
targets
Displays the names and versions of the currently-loaded targets.
udevcomplete cookie
Wake any processes that are waiting for udev to complete pro-
cessing the specified cookie.
udevcomplete_all [age_in_minutes]
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 keys prefixed by two predefined bytes (0x0D4D).
udevcreatecookie
Creates a new cookie to synchronize actions with udev process-
ing. The output is a cookie value. Normally we don't need to
create cookies since dmsetup creates and destroys them for each
action automatically. However, we can generate one explicitly to
group several actions together and use only one cookie instead.
We can define a cookie to use for each relevant command by using
--udevcookie option. Alternatively, we can export this value
into the environment of the dmsetup process as DM_UDEV_COOKIE
variable and it will be used automatically with all subsequent
commands until it is unset. Invoking this command will create
system-wide semaphore that needs to be cleaned up explicitly by
calling udevreleasecookie command.
udevflags cookie
Parses given cookie value and extracts any udev control flags
encoded. The output is in environment key format that is suit-
able for use in udev rules. If the flag has its symbolic name
assigned then the output is DM_UDEV_FLAG_<flag_name>='1',
DM_UDEV_FLAG<flag_position>='1' otherwise. Subsystem udev flags
don't have symbolic names assigned and these ones are always
reported as DM_SUBSYSTEM_UDEV_FLAG<flag_position>='1'. There are
16 udev flags altogether.
udevreleasecookie [cookie]
Waits for all pending udev processing bound to given cookie
value and clean up the 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.
version
Outputs version information.
wait [--noflush] 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 find the last event number.
With --noflush, the thin target (from version 1.3.0) doesn't
commit any outstanding changes to disk before reporting its sta-
tistics.
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>
Simple target types and <target_args> include:
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 0 will 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 or
for creating devices with holes in them.
zero
Returns blocks of zeroes on reads. Any data written is dis-
carded silently. This is a block-device equivalent of the
/dev/zero character-device data sink described in null(4).
More complex targets include:
crypt
Transparent encryption of block devices using the kernel crypto
API.
delay
Delays reads and/or writes to different devices. Useful for
testing.
flakey
Creates a similar mapping to the linear target but exhibits
unreliable behaviour periodically. Useful for simulating fail-
ing devices when testing.
mirror
Mirrors data across two or more devices.
multipath
Mediates access through multiple paths to the same device.
raid
Offers an interface to the kernel's software raid driver, md.
snapshot
Supports snapshots of devices.
To find out more about the various targets and their table formats and
status lines, please read the files in the Documentation/device-mapper
directory in the kernel source tree. (Your distribution might include
a copy of this information in the documentation directory for the
device-mapper package.)
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 (thornber@sistina.com)
SEE ALSO
Device-mapper resource page: http://sources.redhat.com/dm/
Linux Apr 06 2006 DMSETUP(8)
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