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4.3. Configuration File Defaults

The /etc/multipath.conf configuration file includes a defaults section that sets the user_friendly_names parameter to yes, as follows. 
defaults {
        user_friendly_names yes
}
This overwrites the default value of the user_friendly_names parameter.
The configuration file includes a template of configuration defaults. This section is commented out, as follows. 
#defaults {
#       udev_dir                /dev
#       polling_interval        10
#       selector                "round-robin 0"
#       path_grouping_policy    multibus
#       getuid_callout          "/sbin/scsi_id -g -u -s /block/%n"
#       prio_callout            /bin/true
#       path_checker            readsector0
#       rr_min_io               100
#       max_fds                 8192
#       rr_weight               priorities
#       failback                immediate
#       no_path_retry           fail
#       user_friendly_names     yes
#}
To overwrite the default value for any of the configuration parameters, you can copy the relevant line from this template into the defaults section and uncomment it. For example, to overwrite the path_grouping_policy parameter so that it is multibus rather than the default value of failover, copy the appropriate line from the template to the initial defaults section of the configuration file, and uncomment it, as follows. 
defaults {
        user_friendly_names     yes
        path_grouping_policy    multibus
}
Table 4.1, “Multipath Configuration Defaults” describes the attributes that are set in the defaults section of the multipath.conf configuration file. These values are used by DM-Multipath unless they are overwritten by the attributes specified in the devices and multipaths sections of the multipath.conf file.
Table 4.1. Multipath Configuration Defaults
AttributeDescription
udev_dir Specifies the directory where udev device nodes are created. The default value is /udev.
verbosity (Red Hat Enterprise Linux 5.3 and later) Specifies the verbosity level of the command. It can be overridden by the -v command line option. The default value is 2.
polling_interval Specifies the interval between two path checks in seconds. The default value is 5.
selector, path_selector Specifies the default algorithm to use in determining what path to use for the next I/O operation. The default value is round-robin 0. selector and path_selector have the same meaning; the path_selection attribute is supported in Red Hat Enterprise Linux 5.8 and later.
path_grouping_policy
Specifies the default path grouping policy to apply to unspecified multipaths. Possible values include:
failover = 1 path per priority group
multibus = all valid paths in 1 priority group
group_by_serial = 1 priority group per detected serial number
group_by_prio = 1 priority group per path priority value
group_by_node_name = 1 priority group per target node name
The default value is failover.
getuid_callout
Specifies the default program and arguments to call out to obtain a unique path identifier. An absolute path is required.
This parameter accepts the following wildcard values:
%n: replaced with the device name as it appears in sysfs.
%c: replaced with the device name as it appears in /dev (this is different than the sysfs name for CCISS devices). (Red Hat Enterprise Linux 5.8 and later)
%d: replaced with major_nr:minor_nr
%h: replaced with host_nr:bus_nr:target_nr:lun_nr.
The default value of getuid_callout is /sbin/scsi_id -g -u -s /block/%n.
prio_callout Specifies the default program and arguments to call out to obtain a path weight. Weights are summed for each path group to determine the next path group to use in case of failure. "none" is a valid value. This parameter accepts the same wildcard values as getuid_callout.
path_checker Specifies the default method used to determine the state of the paths. Possible values include: readsector0, rdac, tur, cciss_tur, hp_tur (Red Hat Enterprise Linux 5.5 and later), emc_clariion, hp_sw, and directio. The default value is readsector0.
features
The default extra features of multipath devices, using the format: "number_of_features_plus_arguments feature1 ..." Possible values for features include:
queue_if_no_path, which is the same as setting no_path_retry to queue. For information on issues that may arise when using this feature, see Section 5.4, “Issues with queue_if_no_path feature”.
pg_init_retries n: Retry path group initialization up to n times before failing where n is between 1 and 50, inclusive.
pg_init_delay_secs n: Wait n seconds between path group initialization retries where n is between 0 and 50, inclusive.
rr_min_io Specifies the number of I/O requests to route to a path before switching to the next path in the current path group. The default value is 1000.
max_fds (Red Hat Enterprise Linux 5.2 and later) Sets the maximum number of open file descriptors for the multipathd process. In Red Hat Enterprise Linux 5.3, this option allows a value of max, which sets the number of open file descriptors to the system maximum. As of the Red Hat Enterprise Linux 5.9 release, the default value is max, which sets this to the system limit from /proc/sys/fs/nr_open. For earlier releases, if this is not set the maximum number of open file descriptors is taken from the calling process; it is usually 1024. To be safe, this should be set to the maximum number of paths plus 32, if that number is greater than 1024.
rr_weight
If set to priorities, then instead of sending rr_min_io requests to a path before calling selector or path_selector to choose the next path, the number of requests to send is determined by rr_min_io times the path's priority, as determined by the prio_callout program. Currently, there are priority callouts only for devices that use the group_by_prio path grouping policy, which means that all the paths in a path group will always have the same priority.
If set to uniform, all path weights are equal. The default value is uniform.
failback
Specifies path group failback.
A value of 0 or immediate specifies that as soon as there is a path group with a higher priority than the current path group the system switches to that path group.
A numeric value greater than zero specifies deferred failback, expressed in seconds.
A value of manual specifies that failback can happen only with operator intervention.
The default value is manual.
no_path_retry
A numeric value for this attribute specifies the number of times the system should attempt to use a failed path before disabling queueing.
A value of fail indicates immediate failure, without queueing.
A value of queue indicates that queueing should not stop until the path is fixed.
flush_on_last_del (Red Hat Enterprise Linux 5.3 and later) If set to yes, the multipathd daemon will disable queueing when the last path to a device has been deleted. The default value is no.
queue_without_daemon (Red Hat Enterprise Linux 5.3 and later) If set to no, the multipathd daemon will disable queueing for all devices when it is shut down. As of Red Hat Enterprise Linux release 5.9, the default value is no; for earlier releases, the default value is yes.
user_friendly_names If set to yes, specifies that the system should using the bindings file to assign a persistent and unique alias to the multipath, in the form of mpathn. The default location of the bindings file is /var/lib/multipath/bindings, but this can be changed with the bindings_file option. If set to no, specifies that the system should use use the WWID as the alias for the multipath. In either case, what is specified here will be overridden by any device-specific aliases you specify in the multipaths section of the configuration file. The default value is no.
bindings_file (Red Hat Enterprise Linux 5.2 and later) The location of the bindings file that is used with the user_friendly_names option. The default value is /var/lib/multipath/bindings.
mode (Red Hat Enterprise Linux 5.3 and later) The mode to use for the multipath device nodes, in octal. The default value is determined by the process.
uid (Red Hat Enterprise Linux 5.3 and later) The user ID to use for the multipath device nodes. You must use the numeric user ID. The default value is determined by the process.
gid (Red Hat Enterprise Linux 5.3 and later) The group ID to use for the multipath device nodes. You must use the numeric group ID. The default value is determined by the process.
checker_timeout (Red Hat Enterprise Linux 5.5 and later) The timeout value to use for path checkers that issue SCSI commands with an explicit timeout, in seconds. The default value is taken from sys/block/sdx/device/timeout.
pg_prio_calc (Red Hat Enterprise Linux 5.6 and later) If set to avg, sets the priority of path groups to the average of the priorities of the included paths. If set to sum, sets the priority of path groups to the sum of the priorities of the included paths. As of Red Hat Enterprise Linux release 5.9, the default value is avg; for earlier releases, the default value is sum.
log_checker_err (Red Hat Enterprise Linux 5.6 and later) If set to once, a path checker error is logged once at logging level 2 and any later errors are logged at level 3 until the device is restored. If set to always, every path checker error is logged at logging level 2. The default value is always.
fast_io_fail_tmo (Red Hat Enterprise Linux 5.7 and later) The number of seconds the SCSI layer will wait after a problem has been detected on an FC remote port before failing I/O to devices on that remote port. This value should be smaller than the value of dev_loss_tmo. Setting this to off will disable the timeout. The default value is determined by the OS.
dev_loss_tmo (Red Hat Enterprise Linux 5.7 and later) The number of seconds the SCSI layer will wait after a problem has been detected on an FC remote port before removing it from the system. The default value is determined by the OS.
file_timeout (Red Hat Enterprise Linux 5.7 and later) The number of seconds multipath will wait for a necessary file to appear while setting up a multipath device. The default value is 90.
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