| DMSETUP(8) | MAINTENANCE COMMANDS | DMSETUP(8) |
dmsetup — low level logical volume management
dmsetup clear device_name
dmsetup create device_name [-u|--uuid uuid] [--addnodeoncreate|--addnodeonresume] [-n|--notable|--table table|table_file] [--readahead [+]sectors|auto|none]
dmsetup create --concise [concise_device_specification]
dmsetup deps [-o options] [device_name...]
dmsetup help [-c|-C|--columns]
dmsetup info [device_name...]
dmsetup info -c|-C|--columns [--count count] [--interval seconds] [--nameprefixes] [--noheadings] [-o fields] [-O|--sort sort_fields] [--separator separator] [device_name]
dmsetup load device_name [--table table|table_file]
dmsetup ls [--target target_type] [--exec command] [--tree] [-o options]
dmsetup mangle [device_name...]
dmsetup message device_name sector message
dmsetup mknodes [device_name...]
dmsetup reload device_name [--table table|table_file]
dmsetup remove [-f|--force] [--retry] [--deferred] device_name...
dmsetup remove_all [-f|--force] [--deferred]
dmsetup rename device_name new_name
dmsetup rename device_name --setuuid uuid
dmsetup resume device_name... [--addnodeoncreate|--addnodeonresume] [--noflush] [--nolockfs] [--readahead [+]sectors|auto|none]
dmsetup setgeometry device_name cyl head sect start
dmsetup splitname device_name [subsystem]
dmsetup stats command [options]
dmsetup status [--target target_type] [--noflush] [device_name...]
dmsetup suspend [--nolockfs] [--noflush] device_name...
dmsetup table [--concise] [--target target_type] [--showkeys] [device_name...]
dmsetup targets
dmsetup udevcomplete cookie
dmsetup udevcomplete_all [age_in_minutes]
dmsetup udevcookie
dmsetup udevcreatecookie
dmsetup udevflags cookie
dmsetup udevreleasecookie [cookie]
dmsetup version
dmsetup wait [--noflush] device_name [event_nr]
dmsetup wipe_table device_name... [-f|--force] [--noflush] [--nolockfs]
devmap_name major minor
devmap_name major:minor
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 dmsetup tool as devmap_name (which is not normally distributed and is supported only for historical reasons) is equivalent to dmsetup info -c --noheadings -j major -m minor.
--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.
--count count
Specify the number of times to repeat a report. Set this to zero continue
until interrupted. The default interval is one second.
-f|--force
Try harder to complete operation.
-h|--help
Outputs a summary of the commands available, optionally including 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.
--interval seconds
Specify the interval in seconds between successive iterations for repeating
reports. If --interval is specified but --count is not,
reports will continue to repeat until interrupted. The default interval is
one second.
--manglename auto|hex|none
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: auto
(only do the mangling if not mangled yet, do nothing if already mangled,
error on mixed), hex (always do the mangling) and none (no
mangling). Default mode is auto. 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.
Mangling mode could be also set through DM_DEFAULT_NAME_MANGLING_MODE
environment variable.
-j|--major major
Specify the major number.
-m|--minor minor
Specify the minor number.
-n|--notable
When creating a device, don't load any table.
--nameprefixes
Add a "DM_" prefix plus the field name to the output. Useful with
--noheadings to produce a list of field=value pairs that can be used
to set environment variables (for example, in udev(7) rules).
--noheadings Suppress the headings line when using columnar output.
--noflush Do not flush outstading I/O when suspending a device, or do not commit thin-pool metadata when obtaining thin-pool status.
--nolockfs
Do not attempt to synchronize filesystem eg, when suspending a device.
--noopencount
Tell the kernel not to supply the open reference count for the device.
--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 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 automatically. 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.
-S|--select selection
Process only items that match selection criteria. If the command is
producing report output, adding the "selected" column (-o
selected) displays all rows and shows 1 if the row matches the
selection and 0 otherwise. The selection criteria are defined by
specifying column names and their valid values while making use of supported
comparison operators. As a quick help and to see full list of column names
that can be used in selection and the set of supported selection operators,
check the output of
dmsetup info -c -S help command.
--table table
Specify a one-line table directly on the command line. See below for more
information on the table format.
--udevcookie cookie
Use cookie for udev synchronisation. Note: Same cookie should be used for same
type of operations i.e. creation of multiple different devices. It's not
adviced to combine different operations on the single device.
-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.
clear device_name
Destroys the table in the inactive table slot for device_name.
create device_name [-u|--uuid
uuid] [--addnodeoncreate|--addnodeonresume]
[-n|--notable|--table table|table_file]
[--readahead
[+]sectors|auto|none]
Creates a device with the given name. If table or table_file 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 of device_name in subsequent dmsetup commands. If
successful the device will appear in table and for live device the node
/dev/mapper/device_name is created. See below for more information on
the table format.
create --concise
[concise_device_specification]
Creates one or more devices from a concise device specification. Each device
is specified by a comma-separated list: name, uuid, minor number, flags,
comma-separated table lines. Flags defaults to read-write (rw) or may be
read-only (ro). Uuid, minor number and flags are optional so those fields
may be empty. A semi-colon separates specifications of different devices.
Use a backslash to escape the following character, for example a comma or
semi-colon in a name or table. See also CONCISE FORMAT below.
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 including the list of
report fields.
info [device_name...]
Outputs some brief information about the device in the form:
info -c|-C|--columns
[--count count] [--interval seconds]
[--nameprefixes] [--noheadings] [-o fields]
[-O|--sort sort_fields] [--separator
separator] [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 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
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.
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).
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.
remove [-f|--force] [--retry]
[--deferred] device_name...
Removes a device. It will no longer be visible to dmsetup. Open devices cannot
be removed, but adding --force will replace the table with one that
fails all I/O. --deferred will enable deferred removal of open
devices - the device will be removed when the last user closes it. The
deferred removal feature is supported since version 4.27.0 of the
device-mapper driver available in upstream kernel version 3.13. (Use
dmsetup version to check this.) 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. Do NOT combine --force and
--udevcookie, as udev may start to process udev rules in the middle
of error target replacement and result in nondeterministic result.
remove_all [-f|--force]
[--deferred]
Attempts to remove all device definitions i.e. reset the driver. This also
runs mknodes afterwards. Use with care! Open devices cannot be
removed, but adding --force will replace the table with one that
fails all I/O. --deferred will enable deferred removal of open
devices - the device will be removed when the last user closes it. The
deferred removal feature is supported since version 4.27.0 of the
device-mapper driver available in upstream kernel version 3.13.
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] [--noflush]
[--nolockfs] [--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. The
default subsystem is LVM. LVM currently generates device names by
concatenating the names of the Volume Group, Logical Volume and any internal
Layer with a hyphen as separator. Any hyphens within the names are doubled
to escape them. The precise encoding might change without notice in any
future release, so we recommend you always decode using the current version
of this command.
stats command [options]
Manages IO statistics regions for devices. See dmstats(8) for more
details.
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 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 support the --noflush
option. This lets outstanding I/O that has not yet reached the device to
remain unflushed.
table [--concise] [--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 displayed. Real encryption keys are
suppressed in the table output for crypt and integrity targets unless the
--showkeys parameter is supplied. Kernel key references prefixed with
: are not affected by the parameter and get displayed always (crypt
target only). With --concise, the output is presented concisely on a
single line. Commas then separate the name, uuid, minor device number, flags
('ro' or 'rw') and the table (if present). Semi-colons separate devices.
Backslashes escape any commas, semi-colons or backslashes. See CONCISE
FORMAT below.
targets
Displays the names and versions of the currently-loaded targets.
udevcomplete cookie
Wake any processes that are waiting for udev to complete processing 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.
udevcookie
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 processing. 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 suitable 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 statistics.
wipe_table device_name...
[-f|--force] [--noflush] [--nolockfs]
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).
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:
More complex targets include:
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.)
# 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
A concise representation of one of more devices.
- A comma separates the fields of each device.
- A semi-colon separates devices.
<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<dev_name>,<uuid>,<minor>,<flags>,<table>[,<table>+]]
ro Sets the table being loaded for the device read-only
rw Sets the table being loaded for the device read-write
(default)
# A simple linear read-only device
test-linear-small,,,ro,0 2097152 linear /dev/loop0 0, 2097152 2097152 linear
/dev/loop1 0
# Two linear devices
test-linear-small,,,,0 2097152 linear /dev/loop0 0;test-linear-large,,,, 0
2097152 linear /dev/loop1 0, 2097152 2097152 linear /dev/loop2 0
Original version: Joe Thornber <thornber@redhat.com>
dmstats(8), udev(7), udevadm(8)
LVM2 resource page: https://www.sourceware.org/lvm2/
Device-mapper resource page: http://sources.redhat.com/dm/
| Apr 06 2006 | Linux |