/etc/mdadm.conf
.SH DESCRIPTION
.PP
-.B mdadm
+.I mdadm
is a tool for creating, managing, and monitoring RAID devices using the
.B md
driver in Linux.
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,
-.B mdadm
+.I mdadm
will scan these devices (or any devices listed on the command line).
The
Alternatively, a
.B device
-line can contain the word
+line can contain either of both of the words
+.B containers
+and
.BR partitions .
-This will cause
+The word
+.B containers
+will cause
+.I mdadm
+to look for assembled CONTAINER arrays and included them as a source
+for assembling further arrays.
+
+The word
+.I partitions
+will cause
.I mdadm
to read
.I /proc/partitions
.I /dev
to find the name that matches the numbers.
-If no DEVICE line is present, then "DEVICE partitions" is assumed.
+If no DEVICE line is present, then "DEVICE partitions containers" is assumed.
For example:
.IP
.br
DEV /dev/sd*
.br
-DEVICE /dev/discs/disc*/disc
+DEVICE /dev/disk/by-path/pci*
.br
DEVICE partitions
.TP
.B ARRAY
The ARRAY lines identify actual arrays. The second word on the line
-should be the name of the device where the array is normally
+may be the name of the device where the array is normally
assembled, such as
-.BR /dev/md1 .
+.B /dev/md1
+or
+.BR /dev/md/backup .
+If the name does not start with a slash
+.RB (' / '),
+it is treated as being in
+.BR /dev/md/ .
+Alternately the word
+.B <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,
+.I 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:
-
.RS 4
.TP
.B uuid=
.TP
.B 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:
.B mdadm \-\-monitor
will report an array if it is found to have fewer than this number of
spares when
.B spare\-group
name are considered to be part of the same group. The significance of
a group of arrays is that
-.B mdadm
+.I 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.
.TP
.B auto=
-This option declares to
-.B mdadm
-that it should try to create the device file of the array if it
-doesn't already exist, or exists but with the wrong device number.
+This option is rarely needed with mdadm-3.0, particularly if use with
+the Linux kernel v2.6.28 or later.
+It tells
+.I mdadm
+whether to use partitionable array or non-partitionable arrays and,
+in the absence of
+.IR 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",
recognised for comparability with the output of
.BR "mdadm \-Es" .
+.TP
+.B 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.
+
+.TP
+.B 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.
.RE
.TP
.B mailaddr
line gives an E-mail address that alerts should be
sent to when
-.M mdadm
+.I mdadm
is running in
.B \-\-monitor
mode (and was given the
to suppress this symlink creation.
.RE
+.TP
+.B HOMEHOST
+The
+.B homehost
+line gives a default value for the
+.B \-\-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
+.BR <system>,
+.B <none>
+and
+.BR <ignore> .
+If
+.B <system>
+is given, then the
+.BR gethostname ( 2 )
+systemcall is used to get the host name. This is the default.
+
+If
+.B <ignore>
+is given, then a flag is set so that when arrays are being
+auto-assembled the checking of the recorded
+.I homehost
+is disabled.
+If
+.B <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
+.B HOMEHOST
+line.
+
+If
+.B <none>
+is given, then the default of using
+.BR 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.
+.B /dev/md/1_1
+or
+.BR /dev/md/home_0 .
+.TP
+.B AUTO
+A list of names of metadata format can be given, each preceded by a
+plus or minus sign. Also the word
+.I homehost
+is allowed as is
+.I all
+preceded by plus or minus sign.
+.I all
+is usually last.
+
+When
+.I mdadm
+is auto-assembling an array, either via
+.I \-\-assemble
+or
+.I \-\-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
+.I 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
+.I this
+host, and the word
+.I 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
+.BR /dev/md/ .
+
+The known metadata types are
+.BR 0.90 ,
+.BR 1.x ,
+.BR ddf ,
+.BR imsm .
+
+.TP
+.B 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.
+.I Domain
+can be defined through
+.I policy
+line by specifying a domain name for a number of paths from
+.BR /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
+.I domains
+contains all the
+.I domains
+of the new disk or if both arrays have the same
+.IR spare-group .
+
+To update hot plug configuration it is necessary to execute
+.B mdadm \-\-udev\-rules
+command after changing the config file
+
+Key words used in the
+.I POLICY
+line and supported values are:
+
+.RS 7
+.TP
+.B domain=
+any arbitrary string
+.TP
+.B metadata=
+0.9 1.x ddf or imsm
+.TP
+.B path=
+file glob matching anything from
+.B /dev/disk/by-path
+.B type=
+either
+.B disk
+or
+.BR part .
+.TP
+.B action=
+include, re-add, spare, spare-same-slot, or force-spare
+
+.P
+The
+.I action
+item determines the automatic behavior allowed for devices matching the
+.I path
+and
+.I type
+in the same line. If a device matches several lines with different
+.I actions
+then the most permissive will apply. The ordering of policy lines
+is irrelevant to the end result.
+.TP
+.B include
+allows adding a disk to an array if metadata on that disk matches that array
+.TP
+.B re-add
+will include the device in the array if it appears to be a current member
+or a member that was recently removed
+.TP
+.B 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.
+.TP
+.B 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)
+.TP
+.B force-spare
+as above and the disk will become a spare in remaining cases
+.RE
.SH EXAMPLE
DEVICE /dev/sd[bcdjkl]1
.br
DEVICE /dev/hda1 /dev/hdb1
-# /dev/md0 is known by its UID.
+# /dev/md0 is known by its UUID.
.br
ARRAY /dev/md0 UUID=3aaa0122:29827cfa:5331ad66:ca767371
.br
ARRAY /dev/md/home UUID=9187a482:5dde19d9:eea3cc4a:d646ab8b
.br
auto=part
-
+.br
+POLICY domain=domain1 metadata=imsm path=pci-0000:00:1f.2-scsi-*
+.br
+ action=spare
+.br
+POLICY domain=domain1 metadata=imsm path=pci-0000:04:00.0-scsi-[01]*
+.br
+ action=include
+.br
+# One domain comprising of devices attached to specified paths is defined.
+.br
+# Bare device matching first path will be made an imsm spare on hot plug.
+.br
+# If more than one array is created on devices belonging to domain1 and
+.br
+# one of them becomes degraded, then any imsm spare matching any path for
+.br
+# given domain name can be migrated.
+.br
MAILADDR root@mydomain.tld
.br
PROGRAM /usr/sbin/handle\-mdadm\-events
CREATE group=system mode=0640 auto=part\-8
.br
HOMEHOST <system>
+.br
+AUTO +1.x homehost -all
.SH SEE ALSO
.BR mdadm (8),
projects / thirdparty / mdadm.git / blobdiff