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diff --git a/man/dmsetup.8_main b/man/dmsetup.8_main new file mode 100644 index 000000000..4261fc4c1 --- /dev/null +++ b/man/dmsetup.8_main @@ -0,0 +1,1026 @@ +.TH DMSETUP 8 "Apr 06 2006" "Linux" "MAINTENANCE COMMANDS" +. +.SH NAME +. +dmsetup \(em low level logical volume management +. +.SH SYNOPSIS +. +.\".nh +.ad l +.PD 0 +.HP 9 +.B dmsetup +.de CMD_CLEAR +. BR clear +. IR device_name +.. +.CMD_CLEAR +. +.HP +.B dmsetup +.de CMD_CREATE +. ad l +. BR create +. IR device_name +. RB [ -u | \-\-uuid +. IR uuid ] +. RB \%[ \-\-addnodeoncreate | \-\-addnodeonresume ] +. RB \%[ \-n | \-\-notable | \-\-table +. IR \%table | table_file ] +. RB [ \-\-readahead +. RB \%[ + ] \fIsectors | auto | none ] +. ad b +.. +.CMD_CREATE +. +.HP +.B dmsetup +.de CMD_DEPS +. ad l +. BR deps +. RB [ \-o +. IR options ] +. RI [ device_name ...] +. ad b +.. +.CMD_DEPS +. +.HP +.B dmsetup +.de CMD_HELP +. BR help +. RB [ \-c | \-C | \-\-columns ] +.. +.CMD_HELP +. +.HP +.B dmsetup +.de CMD_INFO +. BR info +. RI [ device_name ...] +.. +.CMD_INFO +. +.HP +.B dmsetup +.de CMD_INFOLONG +. ad l +. BR info +. BR \-c | \-C | \-\-columns +. RB [ \-\-count +. IR count ] +. RB [ \-\-interval +. IR seconds ] +. RB \%[ \-\-nameprefixes ] +. RB \%[ \-\-noheadings ] +. RB [ \-o +. IR fields ] +. RB [ \-O | \-\-sort +. IR sort_fields ] +. RB [ \-\-separator +. IR separator ] +. RI [ device_name ] +. ad b +.. +.CMD_INFOLONG +. +.HP +.B dmsetup +.de CMD_LOAD +. ad l +. BR load +. IR device_name +. RB [ \-\-table +. IR table | table_file ] +. ad b +.. +.CMD_LOAD +. +.HP +.B dmsetup +.de CMD_LS +. ad l +. BR ls +. RB [ \-\-target +. IR target_type ] +. RB [ \-\-exec +. IR command ] +. RB [ \-\-tree ] +. RB [ \-o +. IR options ] +. ad b +.. +.CMD_LS +. +.HP +.B dmsetup +.de CMD_MANGLE +. BR mangle +. RI [ device_name ...] +.. +.CMD_MANGLE +. +.HP +.B dmsetup +.de CMD_MESSAGE +. BR message +. IR device_name +. IR sector +. IR message +.. +.CMD_MESSAGE +. +.HP +.B dmsetup +.de CMD_MKNODES +. BR mknodes +. RI [ device_name ...] +.. +.CMD_MKNODES +. +.HP +.B dmsetup +.de CMD_RELOAD +. ad l +. BR reload +. IR device_name +. RB [ \-\-table +. IR table | table_file ] +. ad b +.. +.CMD_RELOAD +. +.HP +.B dmsetup +.de CMD_REMOVE +. ad l +. BR remove +. RB [ \-f | \-\-force ] +. RB [ \-\-retry ] +. RB [ \-\-deferred ] +. IR device_name ... +. ad b +.. +.CMD_REMOVE +. +.HP +.B dmsetup +.de CMD_REMOVE_ALL +. BR remove_all +. RB [ \-f | \-\-force ] +. RB [ \-\-deferred ] +.. +.CMD_REMOVE_ALL +. +.HP +.B dmsetup +.de CMD_RENAME +. BR rename +. IR device_name +. IR new_name +.. +.CMD_RENAME +. +.HP +.B dmsetup +.de CMD_RENAME_UUID +. BR rename +. IR device_name +. BR \-\-setuuid +. IR uuid +.. +.CMD_RENAME_UUID +. +.HP +.B dmsetup +.de CMD_RESUME +. ad l +. BR resume +. IR device_name ... +. RB [ \-\-addnodeoncreate | \-\-addnodeonresume ] +. RB [ \-\-noflush ] +. RB [ \-\-nolockfs ] +. RB \%[ \-\-readahead +. RB \%[ + ] \fIsectors | auto | none ] +. ad b +.. +.CMD_RESUME +. +.HP +.B dmsetup +.de CMD_SETGEOMETRY +. ad l +. BR setgeometry +. IR device_name +. IR cyl +. IR head +. IR sect +. IR start +. ad b +.. +.CMD_SETGEOMETRY +. +.HP +.B dmsetup +.de CMD_SPLITNAME +. BR splitname +. IR device_name +. RI [ subsystem ] +.. +.CMD_SPLITNAME +. +.HP +.B dmsetup +.de CMD_STATS +. BR stats +. IR command +. RI [ options ] +.. +.CMD_STATS +. +.HP +.B dmsetup +.de CMD_STATUS +. ad l +. BR status +. RB [ \-\-target +. IR target_type ] +. RB [ \-\-noflush ] +. RI [ device_name ...] +. ad b +.. +.CMD_STATUS +. +.HP +.B dmsetup +.de CMD_SUSPEND +. ad l +. BR suspend +. RB [ \-\-nolockfs ] +. RB [ \-\-noflush ] +. IR device_name ... +. ad b +.. +.CMD_SUSPEND +. +.HP +.B dmsetup +.de CMD_TABLE +. ad l +. BR table +. RB [ \-\-target +. IR target_type ] +. RB [ \-\-showkeys ] +. RI [ device_name ...] +. ad b +.. +.CMD_TABLE +. +.HP +.B dmsetup +.de CMD_TARGETS +. BR targets +.. +.CMD_TARGETS +. +.HP +.B dmsetup +.de CMD_UDEVCOMPLETE +. BR udevcomplete +. IR cookie +.. +.CMD_UDEVCOMPLETE +. +.HP +.B dmsetup +.de CMD_UDEVCOMPLETE_ALL +. BR udevcomplete_all +. RI [ age_in_minutes ] +.. +.CMD_UDEVCOMPLETE_ALL +. +.HP +.B dmsetup +.de CMD_UDEVCOOKIES +. BR udevcookie +.. +.CMD_UDEVCOOKIES +. +.HP +.B dmsetup +.de CMD_UDEVCREATECOOKIE +. BR udevcreatecookie +.. +.CMD_UDEVCREATECOOKIE +. +.HP +.B dmsetup +.de CMD_UDEVFLAGS +. BR udevflags +. IR cookie +.. +.CMD_UDEVFLAGS +. +.HP +.B dmsetup +.de CMD_UDEVRELEASECOOKIE +. BR udevreleasecookie +. RI [ cookie ] +.. +.CMD_UDEVRELEASECOOKIE +. +.HP +.B dmsetup +.de CMD_VERSION +. BR version +.. +.CMD_VERSION +. +.HP +.B dmsetup +.de CMD_WAIT +. ad l +. BR wait +. RB [ \-\-noflush ] +. IR device_name +. RI [ event_nr ] +. ad b +.. +.CMD_WAIT +. +.HP +.B dmsetup +.de CMD_WIPE_TABLE +. ad l +. BR wipe_table +. IR device_name ... +. RB [ \-f | \-\-force ] +. RB [ \-\-noflush ] +. RB [ \-\-nolockfs ] +. ad b +.. +.CMD_WIPE_TABLE +.PD +.P +.HP +.PD 0 +.B devmap_name \fImajor minor +.HP +.B devmap_name \fImajor:minor +.PD +.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 dmsetup tool as \fBdevmap_name\fP +(which is not normally distributed and is supported +only for historical reasons) is equivalent to +.BI \%dmsetup\ info\ \-c\ \-\-noheadings\ \-j \ major\ \-m \ minor \c +\fR. +.\" dot above here fixes -Thtml rendering for next HP option +. +.SH OPTIONS +. +.HP +.BR \-\-addnodeoncreate +.br +Ensure \fI/dev/mapper\fP node exists after \fBdmsetup create\fP. +. +.HP +.BR \-\-addnodeonresume +.br +Ensure \fI/dev/mapper\fP node exists after \fBdmsetup resume\fP (default with udev). +. +.HP +.BR \-\-checks +.br +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. +. +.HP +.BR \-c | \-C | \-\-columns +.br +Display output in columns rather than as Field: Value lines. +. +.HP +.BR \-\-count +.IR count +.br +Specify the number of times to repeat a report. Set this to zero +continue until interrupted. The default interval is one second. +. +.HP +.BR \-f | \-\-force +.br +Try harder to complete operation. +. +.HP +.BR \-h | \-\-help +.br +Outputs a summary of the commands available, optionally including +the list of report fields (synonym with \fBhelp\fP command). +. +.HP +.BR \-\-inactive +.br +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. +. +.HP +.BR \-\-interval +.IR seconds +.br +Specify the interval in seconds between successive iterations for +repeating reports. If \fB\-\-interval\fP is specified but \fB\-\-count\fP +is not, reports will continue to repeat until interrupted. +The default interval is one second. +. +.HP +.BR \-\-manglename +.BR auto | hex | none +.br +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: +\fBauto\fP (only do the mangling if not mangled yet, do nothing +if already mangled, error on mixed), +\fBhex\fP (always do the mangling) and +\fBnone\fP (no mangling). +Default mode is \fB#DEFAULT_MANGLING#\fP. +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 +\fBDM_DEFAULT_NAME_MANGLING_MODE\fP +environment variable. +. +.HP +.BR \-j | \-\-major +.IR major +.br +Specify the major number. +. +.HP +.BR \-m | \-\-minor +.IR minor +.br +Specify the minor number. +. +.HP +.BR \-n | \-\-notable +.br +When creating a device, don't load any table. +. +.HP +.BR \-\-nameprefixes +.br +Add a "DM_" prefix plus the field name to the output. Useful with +\fB\-\-noheadings\fP to produce a list of +field=value pairs that can be used to set environment variables +(for example, in +.BR udev (7) +rules). +. +.HP +.BR \-\-noheadings +Suppress the headings line when using columnar output. +. +.HP +.BR \-\-noflush +Do not flush outstading I/O when suspending a device, or do not +commit thin-pool metadata when obtaining thin-pool status. +. +.HP +.BR \-\-nolockfs +.br +Do not attempt to synchronize filesystem eg, when suspending a device. +. +.HP +.BR \-\-noopencount +.br +Tell the kernel not to supply the open reference count for the device. +. +.HP +.BR \-\-noudevrules +.br +Do not allow udev to manage nodes for devices in device-mapper directory. +. +.HP +.BR \-\-noudevsync +.br +Do not synchronise with udev when creating, renaming or removing devices. +. +.HP +.BR \-o | \-\-options +.IR options +.br +Specify which fields to display. +. +.HP +.BR \-\-readahead +.RB [ + ] \fIsectors | auto | none +.br +Specify read ahead size in units of sectors. +The default value is \fBauto\fP which allows the kernel to choose +a suitable value automatically. The \fB+\fP 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 \fBnone\fP is equivalent to specifying zero. +. +.HP +.BR \-r | \-\-readonly +.br +Set the table being loaded read-only. +. +.HP +.BR \-S | \-\-select +.IR selection +.br +Display only rows that match \fIselection\fP criteria. All rows are displayed +with the additional "selected" column (\fB-o selected\fP) showing 1 if the row +matches the \fIselection\fP 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 \fBdmsetup\ info\ -c\ -S\ help\fP +command. +. +.HP +.BR \-\-table +.IR table +.br +Specify a one-line table directly on the command line. +See below for more information on the table format. +. +.HP +.BR \-\-udevcookie +.IR cookie +.br +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. +. +.HP +.BR \-u | \-\-uuid +.br +Specify the \fIuuid\fP. +. +.HP +.BR \-y | \-\-yes +.br +Answer yes to all prompts automatically. +. +.HP +.BR \-v | \-\-verbose +.RB [ \-v | \-\-verbose ] +.br +Produce additional output. +. +.HP +.BR \-\-verifyudev +.br +If udev synchronisation is enabled, verify that udev operations get performed +correctly and try to fix up the device nodes afterwards if not. +. +.HP +.BR \-\-version +.br +Display the library and kernel driver version. +.br +. +.SH COMMANDS +. +.HP +.CMD_CLEAR +.br +Destroys the table in the inactive table slot for device_name. +. +.HP +.CMD_CREATE +.br +Creates a device with the given name. +If \fItable\fP or \fItable_file\fP is supplied, the table is loaded and made live. +Otherwise a table is read from standard input unless \fB\-\-notable\fP is used. +The optional \fIuuid\fP 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 \fI/dev/mapper/device_name\fP is created. +See below for more information on the table format. +. +.HP +.CMD_DEPS +.br +Outputs a list of devices referenced by the live table for the specified +device. Device names on output can be customised by following \fIoptions\fP: +\fBdevno\fP (major and minor pair, used by default), +\fBblkdevname\fP (block device name), +\fBdevname\fP (map name for device-mapper devices, equal to blkdevname otherwise). +. +.HP +.CMD_HELP +.br +Outputs a summary of the commands available, optionally including +the list of report fields. +. +.HP +.CMD_INFO +.br +Outputs some brief information about the device in the form: +.RS +.RS + State: SUSPENDED|ACTIVE, READ-ONLY + Tables present: LIVE and/or INACTIVE + Open reference count + Last event sequence number (used by \fBwait\fP) + Major and minor device number + Number of targets in the live table + UUID +.RE +.RE +.HP +.CMD_INFOLONG +.br +Output you can customise. +Fields are comma-separated and chosen from the following list: +.BR name , +.BR major , +.BR minor , +.BR attr , +.BR open , +.BR segments , +.BR events , +.BR uuid . +Attributes are: +.RI ( L )ive, +.RI ( I )nactive, +.RI ( s )uspended, +.RI ( r )ead-only, +.RI read-( w )rite. +Precede the list with '\fB+\fP' to append +to the default selection of columns instead of replacing it. +Precede any sort field with '\fB-\fP' for a reverse sort on that column. +. +.HP +.CMD_LS +.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. +Device names on output can be customised by following options: +\fBdevno\fP (major and minor pair, used by default), +\fBblkdevname\fP (block device name), +\fBdevname\fP (map name for device-mapper devices, equal to blkdevname otherwise). +\fB\-\-tree\fP displays dependencies between devices as a tree. +It accepts a comma-separate list of \fIoptions\fP. +Some specify the information displayed against each node: +.BR device / nodevice ; +.BR blkdevname ; +.BR active ", " open ", " rw ", " uuid . +Others specify how the tree is displayed: +.BR ascii ", " utf ", " vt100 ; +.BR compact ", " inverted ", " notrunc . +. +.HP +.BR load | \c +.CMD_RELOAD +.br +Loads \fItable\fP or \fItable_file\fP into the inactive table slot for device_name. +If neither is supplied, reads a table from standard input. +. +.HP +.CMD_MANGLE +.br +Ensure existing device-mapper \fIdevice_name\fP 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 \fB\-\-manglename\fP 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 \fB\-\-manglename\fP). +. +.HP +.CMD_MESSAGE +.br +Send message to target. If sector not needed use 0. +. +.HP +.CMD_MKNODES +.br +Ensure that the node in \fI/dev/mapper\fP for \fIdevice_name\fP is correct. +If no device_name is supplied, ensure that all nodes in \fI/dev/mapper\fP +correspond to mapped devices currently loaded by the device-mapper kernel +driver, adding, changing or removing nodes as necessary. +. +.HP +.CMD_REMOVE +.br +Removes a device. It will no longer be visible to dmsetup. Open devices +cannot be removed, but adding \fB\-\-force\fP will replace the table with one +that fails all I/O. \fB\-\-deferred\fP 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 \fBdmsetup version\fP +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 \fB\-\-retry\fP +option will cause the operation to be retried for a few seconds before failing. +Do NOT combine +\fB\-\-force\fP and \fB\-\-udevcookie\fP, as udev may start to process udev +rules in the middle of error target replacement and result in nondeterministic +result. +. +.HP +.CMD_REMOVE_ALL +.br +Attempts to remove all device definitions i.e. reset the driver. This also runs +\fBmknodes\fP afterwards. Use with care! Open devices cannot be removed, but +adding \fB\-\-force\fP will replace the table with one that fails all I/O. +\fB\-\-deferred\fP 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. +. +.HP +.CMD_RENAME +.br +Renames a device. +. +.HP +.CMD_RENAME_UUID +.br +Sets the uuid of a device that was created without a uuid. +After a uuid has been set it cannot be changed. +. +.HP +.CMD_RESUME +.br +Un-suspends a device. +If an inactive table has been loaded, it becomes live. +Postponed I/O then gets re-queued for processing. +. +.HP +.CMD_SETGEOMETRY +.br +Sets the device geometry to C/H/S. +. +.HP +.CMD_SPLITNAME +.br +Splits given \fIdevice name\fP into \fIsubsystem\fP 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. +.HP +.CMD_STATS +.br +Manages IO statistics regions for devices. +See +.BR dmstats (8) +for more details. +.HP +.CMD_STATUS +.br +Outputs status information for each of the device's targets. +With \fB\-\-target\fP, only information relating to the specified target type +any is displayed. With \fB\-\-noflush\fP, the thin target (from version 1.3.0) +doesn't commit any outstanding changes to disk before reporting its statistics. + +.HP +.CMD_SUSPEND +.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 \fB\-\-nolockfs\fP is specified. +Some targets such as recent (October 2006) versions of multipath may support +the \fB\-\-noflush\fP option. This lets outstanding I/O that has not yet reached the +device to remain unflushed. +. +.HP +.CMD_TABLE +.br +Outputs the current table for the device in a format that can be fed +back in using the create or load commands. +With \fB\-\-target\fP, only information relating to the specified target type +is displayed. +Real encryption keys are suppressed in the table output for the crypt +target unless the \fB\-\-showkeys\fP parameter is supplied. Kernel key +references prefixed with \fB:\fP are not affected by the parameter and get +displayed always. +. +.HP +.CMD_TARGETS +.br +Displays the names and versions of the currently-loaded targets. +. +.HP +.CMD_UDEVCOMPLETE +.br +Wake any processes that are waiting for udev to complete processing the specified cookie. +. +.HP +.CMD_UDEVCOMPLETE_ALL +.br +Remove all cookies older than the specified number of minutes. +Any process waiting on a cookie will be resumed immediately. +. +.HP +.CMD_UDEVCOOKIES +.br +List all existing cookies. Cookies are system-wide semaphores with keys +prefixed by two predefined bytes (0x0D4D). +. +.HP +.CMD_UDEVCREATECOOKIE +.br +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 +\fB\-\-udevcookie\fP option. Alternatively, we can export this value into the environment +of the dmsetup process as \fBDM_UDEV_COOKIE\fP 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. +. +.HP +.CMD_UDEVFLAGS +.br +Parses given \fIcookie\fP 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. +. +.HP +.CMD_UDEVRELEASECOOKIE +.br +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 \fBDM_UDEV_COOKIE\fP environment variable. +. +.HP +.CMD_VERSION +.br +Outputs version information. +. +.HP +.CMD_WAIT +.br +Sleeps until the event counter for device_name exceeds event_nr. +Use \fB\-v\fP to see the event number returned. +To wait until the next event is triggered, use \fBinfo\fP to find +the last event number. +With \fB\-\-noflush\fP, the thin target (from version 1.3.0) doesn't commit +any outstanding changes to disk before reporting its statistics. +. +.HP +.CMD_WIPE_TABLE +.br +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). +. +.SH TABLE FORMAT +. +Each line of the table specifies a single target and is of the form: +.sp +.I logical_start_sector num_sectors +.B target_type +.I target_args +.sp +Simple target types and target args include: +. +.TP +.B linear \fIdestination_device start_sector +The traditional linear mapping. +.TP +.B striped \fInum_stripes chunk_size \fR[\fIdestination start_sector\fR]... +Creates a striped area. +.br +e.g. striped 2 32 /dev/hda1 0 /dev/hdb1 0 +will map the first chunk (16k) as follows: +.RS +.RS + 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. +.RE +.RE +.TP +.B error +Errors any I/O that goes to this area. Useful for testing or +for creating devices with holes in them. +.TP +.B zero +Returns blocks of zeroes on reads. Any data written is discarded silently. +This is a block-device equivalent of the \fI/dev/zero\fP +character-device data sink described in \fBnull\fP(4). +.P +More complex targets include: +.TP +.B cache +Improves performance of a block device (eg, a spindle) by dynamically +migrating some of its data to a faster smaller device (eg, an SSD). +.TP +.B crypt +Transparent encryption of block devices using the kernel crypto API. +.TP +.B delay +Delays reads and/or writes to different devices. Useful for testing. +.TP +.B flakey +Creates a similar mapping to the linear target but +exhibits unreliable behaviour periodically. +Useful for simulating failing devices when testing. +.TP +.B mirror +Mirrors data across two or more devices. +.TP +.B multipath +Mediates access through multiple paths to the same device. +.TP +.B raid +Offers an interface to the kernel's software raid driver, md. +.TP +.B snapshot +Supports snapshots of devices. +.TP +.BR thin ", " thin-pool +Supports thin provisioning of devices and also provides a better snapshot support. +.P +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.) +. +.SH EXAMPLES +. +# A table to join two disks together +.br +0 1028160 linear /dev/hda 0 +.br +1028160 3903762 linear /dev/hdb 0 +.br +# A table to stripe across the two disks, +.br +# and add the spare space from +.br +# hdb to the back of the volume +.br +0 2056320 striped 2 32 /dev/hda 0 /dev/hdb 0 +.br +2056320 2875602 linear /dev/hdb 1028160 +. +.SH ENVIRONMENT VARIABLES +. +.TP +.B DM_DEV_DIR +The device directory name. +Defaults to "\fI/dev\fP" and must be an absolute path. +.TP +.B DM_UDEV_COOKIE +A cookie to use for all relevant commands to synchronize with udev processing. +It is an alternative to using \fB\-\-udevcookie\fP option. +.TP +.B DM_DEFAULT_NAME_MANGLING_MODE +A default mangling mode. Defaults to "\fB#DEFAULT_MANGLING#\fP" +and it is an alternative to using \fB\-\-manglename\fP option. +. +.SH AUTHORS +. +Original version: Joe Thornber <thornber@redhat.com> +. +.SH SEE ALSO +. +.BR dmstats (8), +.BR udev (7), +.BR udevadm (8) +.P +LVM2 resource page: https://www.sourceware.org/lvm2/ +.br +Device-mapper resource page: http://sources.redhat.com/dm/ |