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MULTIPATH(8) System Manager's Manual MULTIPATH(8)
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 per-
formance reasons.
ARGUMENTS
The device argument restricts multipath's operation to devices matching the given expres-
sion. 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 se-
lects 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 for-
mat 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. This oper-
ation is delegated to the multipathd daemon if it's running.
-F Flush (remove) all unused multipath device maps. This operation is delegated to the
multipathd daemon if it's running.
-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 mul-
tipath 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.
-e Enable all foreign libraries. This overrides the enable_foreign option from multi-
path.conf(5).
-i Ignore WWIDs file when processing devices. If find_multipaths strict or find_multi-
paths 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/bind-
ings.
-q Don't unset the device mapper feature queue_if_no_path for multipath maps. Nor-
mally, multipath would do so if multipathd is not running, because only a running
multipath daemon guarantees that unusable paths are reinstated when they become us-
able again.
-p policy
Force new maps to use the specified policy, overriding the configuration in multi-
path.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 AT opensvc.com> and
others.
Linux 2018-10-10 MULTIPATH(8)
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