Provided by: mdadm_4.2+20230508-7ubuntu1_amd64 bug

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.

       Spaces  can be included in a word using quotation characters.  Either single quotes (') or
       double quotes (") may be used.  All the characters from one quotation  character  to  next
       identical  character  are  protected  and  will not be used to separate words to start new
       quoted strings.  To include a single quote it must be between double quotes.  To include a
       double quote it must be between single quotes.

       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 or 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  in  any  config  file,  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 component 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.  Any subsequent addresses
              are silently ignored.

       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.  There should only be one MAILADDR line  and  it  should  have
              only one address.  Any subsequent addresses are silently ignored.

       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 given only one program.  Any
              subsequent programs are silently ignored.

       CREATE The  create  line gives default values to be used when creating arrays, new members
              of arrays, and device entries for arrays.

              There should only be one create line.   Any  subsequent  lines  will  override  the
              previous settings.

              Keywords used in the CREATE line and supported values are:

           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 version-1 superblocks.

           names=yes
                  Since  Linux  2.6.29 it has been possible to create md devices with a name like
                  md_home rather than just a number,  like  md3.   mdadm  will  use  the  numeric
                  alternative  by  default as other tools that interact with md arrays may expect
                  only numbers.  If names=yes is given in mdadm.conf then mdadm will use  a  name
                  when  appropriate.  If names=no is given, then non-numeric md device names will
                  not be used even if the default changes in a future release of mdadm.

           bbl=no By default, mdadm will reserve space for a bad block list (bbl) on all  devices
                  included  in  or  added  to  any array that supports them.  Setting bbl=no will
                  prevent this, so newly added devices will not have a bad block log.

       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>, <none> and <ignore>.   If  <system>  is
              given,  then  the  gethostname(2) systemcall is used to get the host name.  This is
              the default.

              If <ignore> is given, then a flag is set  so  that  when  arrays  are  being  auto-
              assembled  the checking of the recorded homehost is disabled.  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.  If there are  other  words,  or  other  HOMEHOST  lines,  they  are
              silently ignored.

              If  <none> is given, then the default of using gethostname(2) is over-ridden and no
              homehost name is assumed.

              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.

       HOMECLUSTER
              The homcluster line gives a default value for the --homecluster= option  to  mdadm.
              It  specifies  the  cluster name for the md device.  The md device can be assembled
              only on the cluster  which  matches  the  name  specified.  If  homcluster  is  not
              provided, mdadm tries to detect the cluster name automatically.

              There  should  only be one homecluster line.  Any subsequent lines will be silently
              ignored.

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

              When mdadm is auto-assembling an array, either 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.

              If  the  metadata  indicates that the array was created for this host, and the word
              homehost appears before any other match, then the  array  is  treated  as  a  valid
              candidate for auto-assembly.

              This  can  be  used  to  disable  all auto-assembly (so that only arrays explicitly
              listed in mdadm.conf or on the command line are assembled), or to disable  assembly
              of certain metadata types which might be handled by other software.  It can also be
              used to disable assembly of all foreign arrays - normally such arrays are assembled
              but given a non-deterministic name in /dev/md/.

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

              AUTO  should be given at most once.  Subsequent lines are silently ignored.  Thus a
              later config file in a config directory  will  not  overwrite  the  setting  in  an
              earlier config file.

       POLICY This  is  used  to  specify  what  automatic  behavior  is allowed on devices newly
              appearing in the system and provides a way of marking spares that can be  moved  to
              other  arrays  as  well  as  the  migration domains.  Domain can be defined through
              policy line by specifying a domain name for a number of  paths  from  /dev/disk/by-
              path/.   A  device may belong to several domains. The domain of an array is a union
              of domains of all devices in that array.  A spare can be automatically  moved  from
              one array to another if the set of the destination array's domains contains all the
              domains of the new disk or if both arrays have the same spare-group.

              To update hot plug configuration it is  necessary  to  execute  mdadm  --udev-rules
              command after changing the config file

              Keywords used in the POLICY line and supported values are:

           domain=
                  any arbitrary string

           metadata=
                  0.9 1.x ddf or imsm

           path=  file glob matching anything from /dev/disk/by-path

           type=  either disk or part.

           action=
                  include, re-add, spare, spare-same-slot, or force-spare

           auto=  yes, no, or homehost.

           The  action  item  determines  the automatic behavior allowed for devices matching the
           path and type in the same line.  If a device  matches  several  lines  with  different
           actions  then  the  most  permissive  will  apply.  The  ordering  of  policy lines is
           irrelevant to the end result.

           include
                  allows adding a disk to an array if metadata on that disk matches that array

           re-add will include the device in the array if it appears to be a current member or  a
                  member  that  was  recently  removed and the array has a write-intent-bitmap to
                  allow the re-add functionality.

           spare  as above and additionally: if the device is bare it can become a spare if there
                  is any array that it is a candidate for based on domains and metadata.

           spare-same-slot
                  as above and additionally if given slot was used by an array that went degraded
                  recently  and  the  device  plugged  in  has  no  metadata  then  it  will   be
                  automatically added to that array (or it's container)

           force-spare
                  as above and the disk will become a spare in remaining cases

       PART-POLICY
              This  is  similar  to POLICY and accepts the same keyword assignments.  It allows a
              consistent set of policies to applied to each of the partitions of a device.

              A PART-POLICY line should set type=disk and identify the path to one or  more  disk
              devices.   Each  partition  on these disks will be treated according to the action=
              setting  from this line.  If  a  domain  is  set  in  the  line,  then  the  domain
              associated  with  each  patition  will  be  based  on the domain, but with "-partN"
              appended, when N is the partition number for the partition that was found.

       SYSFS  The SYSFS line lists custom values of MD device's sysfs attributes  which  will  be
              stored  in  sysfs after the array is assembled. Multiple lines are allowed and each
              line has to contain the uuid or the name of the device to which it relates.   Lines
              are applied in reverse order.

           uuid=  hexadecimal  identifier  of MD device. This has to match the uuid stored in the
                  superblock.

           name=  name of the MD device as was given to mdadm when the array was created. It will
                  be ignored if uuid is not empty.

       MONITORDELAY
              The  monitordelay  line gives a delay in seconds mdadm shall wait before pooling md
              arrays when mdadm is running in --monitor mode.  -d/--delay command  line  argument
              takes precedence over the config file.

              If  multiple  MINITORDELAY  lines  are  provided,  only  first  non-zero  value  is
              considered.

FILES

   /etc/mdadm.conf
       The default config file location, used when mdadm is running without --config option.

   /etc/mdadm.conf.d
       The default directory with config files. Used  when  mdadm  is  running  without  --config
       option, after successful reading of the /etc/mdadm.conf default config file. Files in that
       directory are read in lexical order.

   /etc/mdadm/mdadm.conf
       Alternative config file that is read, when mdadm is running without  --config  option  and
       the /etc/mdadm.conf default config file was not opened successfully.

   /etc/mdadm/mdadm.conf.d
       The  alternative directory with config files. Used when mdadm is runninng without --config
       option, after reading the /etc/mdadm/mdadm.conf alternative config  file  whether  it  was
       successful or not. Files in that directory are read in lexical order.

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
       # The name of this array contains a space.
       ARRAY /dev/md9 name='Data Storage'

       POLICY domain=domain1 metadata=imsm path=pci-0000:00:1f.2-scsi-*
                  action=spare
       POLICY domain=domain1 metadata=imsm path=pci-0000:04:00.0-scsi-[01]*
                  action=include
       # One domain comprising of devices attached to specified paths is defined.
       # Bare device matching first path will be made an imsm spare on hot plug.
       # If more than one array is created on devices belonging to domain1 and
       # one of them becomes degraded, then any imsm spare matching any path for
       # given domain name can be migrated.
       MAILADDR root@mydomain.tld
       PROGRAM /usr/sbin/handle-mdadm-events
       CREATE group=system mode=0640 auto=part-8
       HOMEHOST <system>
       AUTO +1.x homehost -all
       SYSFS name=/dev/md/raid5 group_thread_cnt=4 sync_speed_max=1000000
       SYSFS uuid=bead5eb6:31c17a27:da120ba2:7dfda40d group_thread_cnt=4 sync_speed_max=1000000
       MONITORDELAY 60

SEE ALSO

       mdadm(8), md(4).

                                                                                    MDADM.CONF(5)