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Chapter 4. The DM Multipath Configuration File
By default, DM Multipath provides configuration values for the most common uses of multipathing. In addition, DM Multipath includes support for the most common storage arrays that themselves support DM Multipath. For information on the default configuration values, including supported devices, run either of the following commands.
#multipathd show config#multipath -t
You can override the default configuration values for DM Multipath by editing the
/etc/multipath.conf configuration file. If necessary, you can also add a storage array that is not supported by default to the configuration file.
Note
You can run set up multipathing in the
initramfs file system. If you run multipath from the initramfs file system and you make any changes to the multipath configuration files, you must rebuild the initramfs file system for the changes to take effect. For information on rebuilding the initramfs file system with multipath, see Section 3.4, “Setting Up Multipathing in the initramfs File System”.
This chapter provides information on parsing and modifying the
multipath.conf file. It contains sections on the following topics:
- Configuration file overview
- Configuration file blacklist
- Configuration file defaults
- Configuration file multipaths
- Configuration file devices
In the multipath configuration file, you need to specify only the sections that you need for your configuration, or that you wish to change from the default values. If there are sections of the file that are not relevant to your environment or for which you do not need to override the default values, you can leave them commented out, as they are in the initial file.
The configuration file allows regular expression description syntax.
Further information about the configuration file can be found on the
multipath.conf(5) man page.
4.1. Configuration File Overview
The multipath configuration file is divided into the following sections:
- blacklist
- Listing of specific devices that will not be considered for multipath.
- blacklist_exceptions
- Listing of multipath candidates that would otherwise be blacklisted according to the parameters of the blacklist section.
- defaults
- General default settings for DM Multipath.
- multipaths
- Settings for the characteristics of individual multipath devices. These values overwrite what is specified in the
defaultsanddevicessections of the configuration file. - devices
- Settings for the individual storage controllers. These values overwrite what is specified in the
defaultssection of the configuration file. If you are using a storage array that is not supported by default, you may need to create adevicessubsection for your array.
When the system determines the attributes of a multipath device, first it checks the multipath settings, then the devices settings, then the multipath system defaults.
