\"    $NetBSD: dmsetup.8,v 1.3 2016/06/09 09:01:21 abhinav Exp $
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TH DMSETUP 8 "Apr 06 2006" "Linux" "MAINTENANCE COMMANDS"
SH NAME
dmsetup \- low level logical volume management
SH SYNOPSIS
ad l
B dmsetup help
I [-c|-C|--columns]
br
B dmsetup create
I device_name [-u uuid] [--notable | --table <table> | table_file]
br
B dmsetup remove
I [-f|--force] device_name
br
B dmsetup remove_all
I [-f|--force]
br
B dmsetup suspend
I [--nolockfs] [--noflush] device_name
br
B dmsetup resume
I device_name
br
B dmsetup load
I device_name [--table <table> | table_file]
br
B dmsetup clear
I device_name
br
B dmsetup reload
I device_name [--table <table> | table_file]
br
B dmsetup rename
I device_name new_name
br
B dmsetup message
I device_name sector message
br
B dmsetup ls
I [--target target_type] [--exec command] [--tree [-o options]]
br
B dmsetup info
I [device_name]
br
B dmsetup info -c|-C|--columns
I [--noheadings] [--separator separator] [-o fields] [-O|--sort sort_fields]
I [device_name]
br
B dmsetup deps
I [device_name]
br
B dmsetup status
I [--target target_type]
I [device_name]
br
B dmsetup table
I [--target target_type]
I [device_name]
br
B dmsetup wait
I device_name
I [event_nr]
br
B dmsetup mknodes
I [device_name]
br
B dmsetup targets
br
B dmsetup version
br
B dmsetup setgeometry
I device_name cyl head sect start
br

B devmap_name
I major minor
br
B devmap_name
I major:minor
ad b
SH 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 \fBdevmap_name\fP is equivalent to
br
\fBdmsetup info -c --noheadings -j \fImajor\fB -m \fIminor\fP.
SH OPTIONS
IP \fB-c|-C|--columns
br
Display output in columns rather than as Field: Value lines.
IP \fB-j|--major\ \fImajor
br
Specify the major number.
IP \fB-m|--minor\ \fIminor
br
Specify the minor number.
IP \fB-n|--noheadings
br
Suppress the headings line when using columnar output.
IP \fB--noopencount
br
Tell the kernel not to supply the open reference count for the device.
IP \fB--notable
br
When creating a device, don't load any table.
IP \fB-o|--options
br
Specify which fields to display.
IP \fB-r|--readonly
br
Set the table being loaded read-only.
IP \fB--readahead\ [+]<sectors>|auto|none
br
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.
"None" is equivalent to specifying zero.
IP \fB--table\ <table>
br
Specify a one-line table directly on the command line.
IP \fB-u|--uuid
br
Specify the uuid.
IP \fB-v|--verbose\ [-v|--verbose]
br
Produce additional output.
IP \fB--version
br
Display the library and kernel driver version.
SH COMMANDS
IP \fBcreate
I device_name [-u uuid] [--notable | --table <table> | table_file]
br
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 of
device_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.
IP \fBdeps
I [device_name]
br
Outputs a list of (major, minor) pairs for devices referenced by the
live table for the specified device.
IP \fBhelp
I [-c|-C|--columns]
br
Outputs a summary of the commands available, optionally including
the list of report fields.
IP \fBinfo
I [device_name]
br
Outputs some brief information about the device in the form:
br
   State: SUSPENDED|ACTIVE, READ-ONLY
br
   Tables present: LIVE and/or INACTIVE
br
   Open reference count
br
   Last event sequence number (used by \fBwait\fP)
br
   Major and minor device number
br
   Number of targets in the live table
br
   UUID
IP \fBinfo -c|-C|--columns
I [--noheadings] [--separator separator] [-o fields] [-O|--sort sort_fields]
I [device_name]
br
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.
IP \fBls
I [--target target_type]
I [--exec command]
I [--tree [-o options]]
br
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.
--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.
IP \fBload|reload
I device_name [--table <table> | table_file]
br
Loads <table> or table_file into the inactive table slot for device_name.
If neither is supplied, reads a table from standard input.
IP \fBmessage
I device_name sector message
br
Send message to target. If sector not needed use 0.
IP \fBmknodes
I [device_name]
br
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.
IP \fBremove
I [-f|--force] device_name
br
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.
IP \fBremove_all
I [-f|--force]
br
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 \fBmknodes\fP afterwards.
IP \fBrename
I device_name new_name
br
Renames a device.
IP \fBresume
I device_name
br
Un-suspends a device.
If an inactive table has been loaded, it becomes live.
Postponed I/O then gets re-queued for processing.
IP \fBsetgeometry
I device_name cyl head sect start
br
Sets the device geometry to C/H/S.
IP \fBstatus
I [--target target_type]
I [device_name]
br
Outputs status information for each of the device's targets.
With --target, only information relating to the specified target type
is displayed.
IP \fBsuspend
I [--nolockfs] [--noflush]
I device_name
br
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.
IP \fBtable
I [--target target_type]
I [device_name]
br
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.
IP \fBtargets
br
Displays the names and versions of the currently-loaded targets.
IP \fBversion
br
Outputs version information.
IP \fBwait
I device_name
I [event_nr]
br
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 \fBinfo\fP to find
the last event number.
SH TABLE FORMAT
Each line of the table specifies a single target and is of the form:
br
   logical_start_sector num_sectors target_type target_args
br
br

There are currently three simple target types available together
with more complex optional ones that implement snapshots and mirrors.

IP \fBlinear
I destination_device start_sector
br
The traditional linear mapping.

IP \fBstriped
I num_stripes chunk_size [destination start_sector]+
br
Creates a striped area.
br
e.g. striped 2 32 /dev/hda1 0 /dev/hdb1 0
will map the first chunk (16k) as follows:
br
   LV chunk 1 -> hda1, chunk 1
br
   LV chunk 2 -> hdb1, chunk 1
br
   LV chunk 3 -> hda1, chunk 2
br
   LV chunk 4 -> hdb1, chunk 2
br
   etc.

IP \fBerror
br
Errors any I/O that goes to this area.  Useful for testing or
for creating devices with holes in them.

SH EXAMPLES

# A table to join two disks together
br
br
0 1028160 linear /dev/hda 0
br
1028160 3903762 linear /dev/hdb 0


# A table to stripe across the two disks,
br
# and add the spare space from
br
# hdb to the back of the volume

0 2056320 striped 2 32 /dev/hda 0 /dev/hdb 0
br
2056320 2875602 linear /dev/hdb 1028160

SH ENVIRONMENT VARIABLES
TP
\fBDM_DEV_DIR\fP
The device directory name.
Defaults to "/dev" and must be an absolute path.

SH AUTHORS
Original version: Joe Thornber ([email protected])

SH SEE ALSO
Device-mapper resource page: http://sources.redhat.com/dm/

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