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] [device_name]
[--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.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 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 <mangling_mode>
- Mangle any character not on a whitelist using mangling_mode when processing device-mapper device names. The names 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 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.
- --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
- create
- device_name [-u uuid]
[--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 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 settting.
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]
- setgeometry device_name cyl head sect start
-
splitname
device_name [subsystem]
Splits given device name into subsystem constituents. Default subsystem is LVM.
- status
- [--target target_type] [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
- 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.
AUTHORS¶
Original version: Joe Thornber (thornber@sistina.com)SEE ALSO¶
Device-mapper resource page: http://sources.redhat.com/dm/Apr 06 2006 | Linux |