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
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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: |
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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.
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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.
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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.
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CREATE | |||||||||||||||||||||||||||||||||||||||||||||
The
create line gives default values to be used when creating arrays and device entries for
arrays.
These include:
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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
gethostname(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 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. 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 assembled), 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.
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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