NAME

       multipath - Device mapper target autoconfig.

SYNOPSIS

       multipath [-v level] [-B|-d|-i|-q|-r] [-b file] [-p policy] [device]

       multipath [-v level] [-R retries] -f device

       multipath [-v level] [-R retries] -F

       multipath [-v level] [-l|-ll] [device]

       multipath [-v level] [-a|-w] device

       multipath [-v level] -W

       multipath [-v level] [-i] [-c|-C] device

       multipath [-v level] [-i] [-u|-U]

       multipath [-h|-t|-T]

DESCRIPTION

       multipath  is  used  to  detect  and  coalesce multiple paths to devices, for fail-over or
       performance reasons.

ARGUMENTS

       The device  argument  restricts  multipath's  operation  to  devices  matching  the  given
       expression.  The  argument  may  refer  either  to  a  multipath  map or to its components
       ("paths"). The expression may be in one of the following formats:

       device node   file name of a device node, e.g. /dev/dm-10 or /dev/sda. If the node  refers
                     to  an  existing  device  mapper  device  representing a multipath map, this
                     selects the map or its paths, depending on the operation mode. Otherwise, it
                     selects a path device.

       device ID     kernel  device  number  specified  by  major:minor numbers, e.g. 65:16. This
                     format can only be used for path devices.

       WWID          a World Wide Identifier matching a multipath map or its paths. To list WWIDs
                     of  devices  present  in  the system, use e.g. the command "multipath -d -v3
                     2>/dev/null".

OPERATION MODES

       The default operation mode is to detect and set up multipath maps from the  devices  found
       in  the  system.   Other  operation modes are chosen by using one of the following command
       line switches:

       -f     Flush (remove) a multipath device map specified as parameter, if unused.

       -F     Flush (remove) all unused multipath device maps.

       -l     Show ("list") the current multipath topology from information fetched in sysfs  and
              the device mapper.

       -ll    Show ("list") the current multipath topology from all available information (sysfs,
              the device mapper, path checkers ...).

       -a     Add the WWID for the specified device to the WWIDs file.

       -w     Remove the WWID for the specified device from the WWIDs file.

       -W     Reset the WWIDs file to only include the current multipath devices.

       -c     Check if a block device should be a path in a multipath device.

       -C     Check if a multipath device has usable paths. This can be used to test  whether  or
              not  I/O on this device is likely to succeed. The command itself doesn't attempt to
              do I/O on the device.

       -u     Check if the device specified in the program environment should  be  a  path  in  a
              multipath device.

       -U     Check if the device specified in the program environment is a multipath device with
              usable paths. See -C.

       -h     Print usage text.

       -t     Display the currently used multipathd configuration.

       -T     Display the currently used multipathd configuration, limiting the output  to  those
              devices  actually  present  in the system. This can be used a template for creating
              multipath.conf.

OPTIONS

       -v level
              Verbosity of information printed to stdout in default and "list"  operation  modes.
              The default level is -v 2.

                   0           Nothing is printed.

                   1           In default mode, Names/WWIDs of created or modified multipath maps
                               are printed. In  list  mode,  WWIDs  of  all  multipath  maps  are
                               printed.

                   2           In default mode, Topology of created or modified multipath maps is
                               printed.  In list mode, topology of all multipath maps is printed.

                   3           All detected paths and the topology  of  all  multipath  maps  are
                               printed.

                   The  verbosity level also controls the level of log and debug messages printed
                   to stderr. The default level corresponds  to  LOG_NOTICE  (important  messages
                   that shouldn't be missed in normal operation).

       -d     Dry run, do not create or update devmaps.

       -i     Ignore   WWIDs   file   when  processing  devices.  If  find_multipaths  strict  or
              find_multipaths no is set in multipath.conf, multipath only considers devices  that
              are listed in the WWIDs file. This option overrides that behavior. For other values
              of  find_multipaths,  this  option  has  no  effect.   See   the   description   of
              find_multipaths  in  multipath.conf(5).   This  option  should only be used in rare
              circumstances.

       -B     Treat the bindings file as read only.

       -b file
              Set   user_friendly_names    bindings    file    location.     The    default    is
              /etc/multipath/bindings.

       -q     Don't  unset  the  device  mapper  feature  queue_if_no_path  for  multipath  maps.
              Normally, multipath would do so if  multipathd  is  not  running,  because  only  a
              running  multipath  daemon  guarantees that unusable paths are reinstated when they
              become usable again.

       -p policy
              Force new maps to  use  the  specified  policy,  overriding  the  configuration  in
              multipath.conf(5).  The  possible  values for policy are the same as the values for
              path_grouping_policy in multipath.conf(5). Existing maps are not modified.

       -r     Force a reload of all existing multipath maps. This command  is  delegated  to  the
              multipathd daemon if it's running. In this case, other command line switches of the
              multipath command have no effect.

       -R retries
              Number of times to retry flushing multipath devices that are in use. The default is
              0.

SEE ALSO

       multipathd(8), multipath.conf(5), kpartx(8), udev(8), dmsetup(8), hotplug(8).

AUTHORS

       multipath-tools  was  developed by Christophe Varoqui <christophe.varoqui@opensvc.com> and
       others.