5:mdadm.conf
From Linux Man Pages
mdadm.conf - configuration for management of Software Raid with mdadm
/etc/mdadm.conf
Contents |
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 the word partitions. This will cause mdadm to read /proc/parti-
tions and include all devices and partitions found there-in. mdadm does not use the names from /proc/par-
titions but only the major and minor device numbers. It scans /dev to find the name that matches the num-
bers.
If no DEVICE line is present, then "DEVICE partitions" is assumed.
For example:
DEVICE /dev/hda* /dev/hdc*
DEV /dev/sd*
DEVICE /dev/discs/disc*/disc
DEVICE partitions
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 assembled, such as /dev/md1. 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 com-
patibility with the output of
mdadm --examine --scan.
spares=
The value is a number of spare devices to expect the array to have. 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 con-
sidered 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 declares to 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.
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.
MAILADDR
The mailaddr line gives an E-mail address that alerts should be sent to when 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 abbreviate at leat 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 interest-
ing 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 version-1 superblocks.
EXAMPLE
DEVICE /dev/sd[bcdjkl]1
DEVICE /dev/hda1 /dev/hdb1
# /dev/md0 is known by it's UID.
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 precisey 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>
RELATED
mdadm(8), md(4).