dmsetup.8

Linux Device Mapper Source Code

.TH DMSETUP 8 "Apr 06 2006" "Linux" "MAINTENTANCE 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--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 processess 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 AUTHORS
Original version: Joe Thornber ([e-mail])

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