table of contents
DMSETUP(8) | MAINTENANCE COMMANDS | DMSETUP(8) |
NAME¶
dmsetup — low level logical volume managementSYNOPSIS¶
dmsetup clear device_nametable_file]
[{--addnodeoncreate|--addnodeonresume}] [--readahead
[+]<sectors>|auto|none]
[-o fields] [-O|--sort
sort_fields] [-S|--select Selection]
[device_name]
[-o options]
[--readahead
[+]<sectors>|auto|none]
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 toOPTIONS¶
- --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 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.
- --manglename {none|hex|auto}
- 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) 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.
- --noheadings
- Suppress the headings line when using columnar output.
- --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
- 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
- Display only rows that match Selection criteria. All rows are displayed with the additional "selected" column (-o selected) showing 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.
- --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.
COMMANDS¶
- clear
- device_name
- create
- device_name [-u uuid]
[-n|--notable|--table
<table>|table_file]
[{--addnodeoncreate|--addnodeonresume}] [--readahead
[+]<sectors>|auto|none]
- deps
- [-o options] [device_name]
- help
- [-c|-C|--columns]
- info
- [device_name]
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]
- ls
- [--target target_type] [--exec command]
[--tree] [-o options]
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.
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]
[--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}]
[--readahead
[+]<sectors>|auto|none]
- setgeometry device_name cyl head sect start
-
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.
- status
- [--target target_type] [--noflush]
[device_name]
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
- [--target target_type] [--showkeys]
[device_name]
- 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.
udevcookies
List all existing cookies. Cookies are system-wide semaphores with keys prefixed
by two predefined bytes (0x0D4D).
- udevcreatecookie
-
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
-
- wait
- [--noflush] device_name [event_nr]
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
-
- zero
-
- crypt
-
- delay
-
- flakey
-
- mirror
-
multipath
Mediates access through multiple paths to the same device.
- raid
-
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 togetherENVIRONMENT 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.
- DM_DEFAULT_NAME_MANGLING_MODE
- A default mangling mode. Defaults to "auto" and it is an alternative to using --manglename option.
AUTHORS¶
Original version: Joe Thornber (thornber@redhat.com)SEE ALSO¶
LVM2 resource page https://www.sourceware.org/lvm2/Apr 06 2006 | Linux |