MDADM.CONF(5)							File Formats Manual						     MDADM.CONF(5)

NAME

       mdadm.conf - configuration for management of Software RAID with mdadm

SYNOPSIS

       /etc/mdadm.conf

DESCRIPTION

       mdadm is a tool for creating, managing, and monitoring RAID devices using the md driver in Linux.

       Some common tasks, such as assembling all arrays, can be simplified by describing the devices and arrays in this configuration file.

   SYNTAX
       The  file should be seen as a collection of words separated by white space (space, tab, or newline).  Any word that beings with a hash sign
       (#) starts a comment and that word together with the remainder of the line is ignored.

       Any line that starts with white space (space or tab) is treated as though it were a continuation of the previous line.

       Empty lines are ignored, but otherwise each (non continuation) line must start with a keyword as  listed  below.   The  keywords  are  case
       insensitive and can be abbreviated to 3 characters.

       The keywords are:

       DEVICE A  device  line lists the devices (whole devices or partitions) that might contain a component of an MD array.  When looking for the
	      components of an array, mdadm will scan these devices (or any devices listed on the command line).

	      The device line may contain a number of different devices (separated by spaces) and each device  name  can  contain  wild  cards	as
	      defined by glob(7).

	      Also, there may be several device lines present in the file.

	      Alternatively,  a  device  line  can contain either of both of the  words containers and partitions.  The word containers will cause
	      mdadm to look for assembled CONTAINER arrays and included them as a source for assembling further arrays.

	      The word partitions will cause mdadm to read /proc/partitions and include all devices and partitions found therein.  mdadm does  not
	      use  the	names  from /proc/partitions but only the major and minor device numbers.  It scans /dev to find the name that matches the
	      numbers.

	      If no DEVICE line is present, then "DEVICE partitions containers" is assumed.

	      For example:

	      DEVICE /dev/hda* /dev/hdc*
	      DEV    /dev/sd*
	      DEVICE /dev/disk/by-path/pci*
	      DEVICE partitions

       ARRAY  The ARRAY lines identify actual arrays.  The second word on the line may be the name of the  device  where  the  array  is  normally
	      assembled,  such	as /dev/md1 or /dev/md/backup.	If the name does not start with a slash ('/'), it is treated as being in /dev/md/.
	      Alternately the word <ignore> (complete with angle brackets) can be given in which case any array which matches the rest of the line
	      will  never  be  automatically assembled.  If no device name is given, mdadm will use various heuristics to determine an appropriate
	      name.

	      Subsequent words identify the array, or identify the array as a member of a group. If multiple identities are given, then  a  compo-
	      nent device must match ALL identities to be considered a match.  Each identity word has a tag, and equals sign, and some value.  The
	      tags are:

	   uuid=  The value should be a 128 bit uuid in hexadecimal, with punctuation interspersed if desired.	This must match the uuid stored in
		  the superblock.

	   name=  The  value should be a simple textual name as was given to mdadm when the array was created.	This must match the name stored in
		  the superblock on a device for that device to be included in the array.  Not all superblock formats support names.

	   super-minor=
		  The value is an integer which indicates the minor number that was stored in the superblock when the array was created.  When	an
		  array is created as /dev/mdX, then the minor number X is stored.

	   devices=
		  The  value  is a comma separated list of device names or device name patterns.  Only devices with names which match one entry in
		  the list will be used to assemble the array.	Note that the devices listed there must also be listed on a DEVICE line.

	   level= The value is a raid level.  This is not normally used to identify an array, but is supported so that the output of

		  mdadm --examine --scan

		  can be use directly in the configuration file.

	   num-devices=
		  The value is the number of devices in a complete active array.  As with level= this is mainly for compatibility with the  output
		  of

		  mdadm --examine --scan.

	   spares=
		  The value is a number of spare devices to expect the array to have.  The sole use of this keyword and value is as follows: mdadm
		  --monitor will report an array if it is found to have fewer than this number of spares when --monitor starts or  when  --oneshot
		  is used.

	   spare-group=
		  The  value  is a textual name for a group of arrays.	All arrays with the same spare-group name are considered to be part of the
		  same group.  The significance of a group of arrays is that mdadm will, when monitoring the arrays, move a spare drive  from  one
		  array in a group to another array in that group if the first array had a failed or missing drive but no spare.

	   auto=  This option is rarely needed with mdadm-3.0, particularly if use with the Linux kernel v2.6.28 or later.  It tells mdadm whether
		  to use partitionable array or non-partitionable arrays and, in the absence of udev, how many partition devices to create.   From
		  2.6.28 all md array devices are partitionable, hence this option is not needed.

		  The  value  of this option can be "yes" or "md" to indicate that a traditional, non-partitionable md array should be created, or
		  "mdp", "part" or "partition" to indicate that a partitionable md array (only available in linux 2.6 and later) should  be  used.
		  This later set can also have a number appended to indicate how many partitions to create device files for, e.g.  auto=mdp5.  The
		  default is 4.

	   bitmap=
		  The option specifies a file in which a write-intent bitmap should be found.  When assembling the array, mdadm will provide  this
		  file to the md driver as the bitmap file.  This has the same function as the --bitmap-file option to --assemble.

	   metadata=
		  Specify the metadata format that the array has.  This is mainly recognised for comparability with the output of mdadm -Es.

	   container=
		  Specify  that  this  array is a member array of some container.  The value given can be either a path name in /dev, or a UUID of
		  the container array.

	   member=
		  Specify that this array is a member array of some container.	Each type of container has some way to	enumerate  member  arrays,
		  often  a  simple  sequence  number.  The value identifies which member of a container the array is.  It will usually accompany a
		  "container=" word.

       MAILADDR
	      The mailaddr line gives an E-mail address that alerts should be sent to when mdadm is running in --monitor mode (and was	given  the
	      --scan option).  There should only be one MAILADDR line and it should have only one address.

       MAILFROM
	      The  mailfrom  line  (which  can	only be abbreviated to at least 5 characters) gives an address to appear in the "From" address for
	      alert mails.  This can be useful if you want to explicitly set a domain, as the default from address is "root" with no domain.   All
	      words on this line are catenated with spaces to form the address.

	      Note that this value cannot be set via the mdadm commandline.  It is only settable via the config file.

       PROGRAM
	      The  program  line  gives  the name of a program to be run when mdadm --monitor detects potentially interesting events on any of the
	      arrays that it is monitoring.  This program gets run with two or three arguments, they being the Event, the md device, and  possibly
	      the related component device.

	      There should only be one program line and it should be give only one program.

       CREATE The create line gives default values to be used when creating arrays and device entries for arrays.  These include:

	   owner=

	   group= These can give user/group ids or names to use instead of system defaults (root/wheel or root/disk).

	   mode=  An octal file mode such as 0660 can be given to override the default of 0600.

	   auto=  This	corresponds  to  the  --auto  flag to mdadm.  Give yes, md, mdp, part -- possibly followed by a number of partitions -- to
		  indicate how missing device entries should be created.

	   metadata=
		  The name of the metadata format to use if none is explicitly given.  This can be useful to impose a system-wide default of  ver-
		  sion-1 superblocks.

	   symlinks=no
		  Normally when creating devices in /dev/md/ mdadm will create a matching symlink from /dev/ with a name starting md or md_.  Give
		  symlinks=no to suppress this symlink creation.

       HOMEHOST
	      The homehost line gives a default value for the --homehost= option to mdadm.  There should normally be only one other  word  on  the
	      line.   It should either be a host name, or one of the special words <system> and <ignore>.  If <system> is given, then the gethost-
	      name(2) systemcall is used to get the host name.

	      If <ignore> is given, then a flag is set so that when arrays are being auto-assembled the checking of the recorded homehost is  dis-
	      abled.  If <ignore> is given it is also possible to give an explicit name which will be used when creating arrays.  This is the only
	      case when there can be more that one other word on the HOMEHOST line.

	      When arrays are created, this host name will be stored in the metadata.  When arrays are assembled using auto-assembly, arrays which
	      do  not  record  the  correct homehost name in their metadata will be assembled using a "foreign" name.  A "foreign" name alway ends
	      with a digit string preceded by an underscore to differentiate it from any possible local name. e.g.  /dev/md/1_1 or /dev/md/home_0.

       AUTO   A list of names of metadata format can be given, each preceded by a plus or minus sign.  Also the word all preceded by plus or minus
	      is allowed and is usually last.

	      When  mdadm  is auto-assembling an array, with via --assemble or --incremental and it finds metadata of a given type, it checks that
	      metadata type against those listed in this line.	The first match wins, where all matches anything.  If a match is  found  that  was
	      preceded	by a plus sign, the auto assembly is allowed.  If the match was preceded by a minus sign, the auto assembly is disallowed.
	      If no match is found, the auto assembly is allowed.

	      This can be used to disable all auto-assembly (so that only arrays explicitly listed in mdadm.conf or on the command line are assem-
	      bled), or to disable assembly of certain metadata types which might be handled by other software.

	      The known metadata types are 0.90, 1.x, ddf, imsm.

EXAMPLE

       DEVICE /dev/sd[bcdjkl]1
       DEVICE /dev/hda1 /dev/hdb1

       # /dev/md0 is known by its UUID.
       ARRAY /dev/md0 UUID=3aaa0122:29827cfa:5331ad66:ca767371
       # /dev/md1 contains all devices with a minor number of
       #   1 in the superblock.
       ARRAY /dev/md1 superminor=1
       # /dev/md2 is made from precisely these two devices
       ARRAY /dev/md2 devices=/dev/hda1,/dev/hdb1

       # /dev/md4 and /dev/md5 are a spare-group and spares
       #  can be moved between them
       ARRAY /dev/md4 uuid=b23f3c6d:aec43a9f:fd65db85:369432df
		  spare-group=group1
       ARRAY /dev/md5 uuid=19464854:03f71b1b:e0df2edd:246cc977
		  spare-group=group1
       # /dev/md/home is created if need to be a partitionable md array
       # any spare device number is allocated.
       ARRAY /dev/md/home UUID=9187a482:5dde19d9:eea3cc4a:d646ab8b
		  auto=part

       MAILADDR root@mydomain.tld
       PROGRAM /usr/sbin/handle-mdadm-events
       CREATE group=system mode=0640 auto=part-8
       HOMEHOST <system>
       AUTO +1.x -all

SEE ALSO

       mdadm(8), md(4).

																     MDADM.CONF(5)