.\" -*- nroff -*-
-.TH mdadm 8
+.TH MDADM 8 "" v1.6.0
.SH NAME
mdadm \- manage MD devices
.I aka
.SH SYNOPSIS
-.BI mdadm " [mode] <raiddevice> [options] <subdevices>"
+.BI mdadm " [mode] <raiddevice> [options] <component-devices>"
.SH DESCRIPTION
RAID devices are virtual devices created from two or more
real block devices. This allows multiple devices (typically disk
drives or partitions there-of) to be combined into a single device to
hold (for example) a single filesystem.
-Some RAID levels included redundancy and so can survive some degree of
+Some RAID levels include redundancy and so can survive some degree of
device failure.
-Linux Software RAID devices are implemented through the md (Multiple Devices) device driver.
+Linux Software RAID devices are implemented through the md (Multiple
+Devices) device driver.
Currently, Linux supports
.B LINEAR
(striping),
.B RAID1
(mirroring),
-.B RAID4
+.BR RAID4 ,
+.BR RAID5 ,
+.BR RAID6 ,
and
-.B RAID5.
-
-Recent kernels (2002) also support a mode known as
.BR MULTIPATH .
-.B mdadm
-does not support MULTIPATH as yet.
+
+.B MULTIPATH is not a Software RAID mechanism, but does involve
+multiple devices. For
+.B MULTIPATH
+each device is a path to one common physical storage device.
+
.B mdadm
-is a program that can be used to create and manage MD devices. As
+is a program that can be used to create, manage, and monitor
+MD devices. As
such it provides a similar set of functionality to the
.B raidtools
packages.
.IP \(bu 4
.B mdadm
can perform (almost) all of its functions without having a
-configuration file. Also mdadm helps with management of the configuration
+configuration file and does not use one by default. Also
+.B mdadm
+helps with management of the configuration
file.
.IP \(bu 4
.B mdadm
-can provide information about your arrays (through Detail and Examine)
+can provide information about your arrays (through Query, Detail, and Examine)
that
.B raidtools
cannot.
-.IP \(bu 4
+.P
+.I mdadm
+does not use
+.IR /etc/raidtab ,
+the
.B raidtools
-can manage MULTIPATH devices which
-.B mdadm
-cannot yet manage.
+configuration file, at all. It has a different configuration file
+with a different format and an different purpose.
.SH MODES
mdadm has 7 major modes of operation:
'''in several step create-add-add-run or it can all happen with one command.
.TP
-.B Detail
-Display the details of a given md device. Details include the RAID
-level, the number of devices, which ones are faulty (if any), and the
-array UUID.
+.B Manage
+This is for doing things to specific components of an array such as
+adding new spares and removing faulty devices.
.TP
-.B Examine
-Examine a device to see if it is part of an md array, and print out
-the details of that array.
-This mode can also be used to examine a large number of devices and to
-print out a summary of the arrays found in a format suitable for the
-.B mdadm.conf
-configuration file.
+.B Misc
+This mode allows operations on independent devices such as examine MD
+superblocks, erasing old superblocks and stopping active arrays.
.TP
.B "Follow or Monitor"
-Monitor one or more md devices and act on any state changes.
+Monitor one or more md devices and act on any state changes. This is
+only meaningful for raid1, 4, 5, 6 or multipath arrays as
+only these have interesting state. raid0 or linear never have
+missing, spare, or failed drives, so there is nothing to monitor.
.TP
-.B Manage
-This is for odd bits an pieces like hotadd, hotremove, setfaulty, stop,
-readonly, readwrite.
-'''If an array is only partially setup by the
-'''Create or Assemble commands, subsequent Manage commands can finish the
-'''job.
+.B "Grow"
+Grow (or shrink) an array, or otherwise reshape it in some way.
+Currently supported growth options including changing the active size
+of componenet devices in RAID level 1/4/5/6 and changing the number of
+active devices in RAID1.
.SH OPTIONS
.TP
.BR -A ", " --assemble
-Assemble an existing array.
+Assemble a pre-existing array.
.TP
.BR -B ", " --build
.BR -C ", " --create
Create a new array.
+.TP
+.BR -Q ", " --query
+Examine a device to see
+(1) if it is an md device and (2) if it is a component of an md
+array.
+Information about what is discovered is presented.
+
.TP
.BR -D ", " --detail
Print detail of one or more md devices.
.B Monitor
mode.
+.TP
+.BR -G ", " --grow
+Change the size or shape of an active array.
+
.TP
.BR -h ", " --help
-Display help message or, after above option, mode specific help message.
+Display help message or, after above option, mode specific help
+message.
+
+.TP
+.B --help-options
+Display more detailed help about command line parsing and some commonly
+used options.
.TP
.BR -V ", " --version
and
.BR --examine .
+.TP
+.BR -f ", " --force
+Be more forceful about certain operations. See the various modes of
+the exact meaning of this option in different contexts.
+
+.TP
+.BR -c ", " --config=
+Specify the config file. Default is
+.BR /etc/mdadm.conf .
+If the config file given is
+.B partitions
+then nothing will be read, but
+.I mdadm
+will act as though the config file contained exactly
+.B "DEVICE partitions"
+and will read
+.B /proc/partitions
+to find a list of devices to scan.
+If the word
+.B none
+is given for the config file, then
+.I mdadm
+will act as though the config file were empty.
+
+.TP
+.BR -s ", " --scan
+scan config file or
+.B /proc/mdstat
+for missing information.
+In general, this option gives
+.B mdadm
+permission to get any missing information, like component devices,
+array devices, array identities, and alert destination from the
+configuration file:
+.BR /etc/mdadm.conf .
+One exception is MISC mode when using
+.B --detail
+or
+.B --stop
+in which case
+.B --scan
+says to get a list of array devices from
+.BR /proc/mdstat .
+
.SH For create or build:
.TP
.TP
.BR -l ", " --level=
-Set raid level. Options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid5, 4,
-raid5, 5. Obviously some of these are synonymous.
-Only the first 4 are valid when Building.
+Set raid level. When used with
+.IR --create ,
+options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
+raid5, 5, raid6, 6, multipath, mp. Obviously some of these are synonymous.
+
+When used with
+.IR --build ,
+only linear, raid0, 0, stripe are valid.
.TP
.BR -p ", " --parity=
Set raid5 parity algorithm. Options are:
-{left,right}-{,a}symmetric, la, ra, ls, rs. The default is left-symmetric.
+left-asymmetric,
+left-symmetric,
+right-asymmetric,
+right-symmetric,
+la, ra, ls, rs. The default is left-symmetric.
.TP
.BR --layout=
same as --parity
.TP
-.BR -n ", " --raid-disks=
-number of active devices in array.
+.BR -n ", " --raid-devices=
+Specify the number of active devices in the array. This, plus the
+number of spare devices (see below) must equal the number of
+.I component-devices
+(including "\fBmissing\fP" devices)
+that are listed on the command line for
+.BR --create .
+Setting a value of 1 is probably
+a mistake and so requires that
+.B --force
+be specified first. A value of 1 will then be allowed for linear,
+multipath, raid0 and raid1. It is never allowed for raid4 or raid5.
+.br
+This number can only be changed using
+.B --grow
+for RAID1 arrays, and only on kernels which provide necessary support.
.TP
-.BR -x ", " --spare-disks=
-number of spare (eXtra) disks in initial array. Spares can be added
-and removed later.
+.BR -x ", " --spare-devices=
+Specify the number of spare (eXtra) devices in the initial array.
+Spares can also be added
+and removed later. The number of component devices listed
+on the command line must equal the number of raid devices plus the
+number of spare devices.
+
.TP
.BR -z ", " --size=
-Amount (in Kibibytes) of space to use from each drive in RAID1/4/5.
+Amount (in Kibibytes) of space to use from each drive in RAID1/4/5/6.
This must be a multiple of the chunk size, and must leave about 128Kb
of space at the end of the drive for the RAID superblock.
If this is not specified
size, though if there is a variance among the drives of greater than 1%, a warning is
issued.
+This value can be set with
+.B --grow
+for RAID level 1/4/5/6. If the array was created with a size smaller
+than the currently active drives, the extra space can be accessed
+using
+.BR --grow .
+
+.TP
+.BR --assume-clean
+Tell
+.I mdadm
+that the array pre-existed and is known to be clean. This is only
+really useful for Building RAID1 array. Only use this if you really
+know what you are doing. This is currently only supported for --build.
+
+.TP
+.BR -R ", " --run
+Insist that
+.I mdadm
+run the array, even if some of the components
+appear to be active in another array or filesystem. Normally
+.I mdadm
+will ask for confirmation before including such components in an
+array. This option causes that question to be suppressed.
+
+.TP
+.BR -f ", " --force
+Insist that
+.I mdadm
+accept the geometry and layout specified without question. Normally
+.I mdadm
+will not allow creation of an array with only one device, and will try
+to create a raid5 array with one missing drive (as this makes the
+initial resync work faster). With
+.BR --force ,
+.I mdadm
+will not try to be so clever.
+
+.TP
+.BR -a ", " "--auto{=no,yes,md,mdp,part,p}{NN}"
+Instruct mdadm to create the device file if needed, and to allocate
+an unused minor number. "yes" or "md" causes a non-partitionable array
+to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and
+later) to be used. The argumentment can also come immediately after
+"-a". e.g. "-ap".
+
+For partitionable arrays,
+.I mdadm
+will create the device file for the whole array and for the first 4
+partitions. A different number of partitions can be specified at the
+end of this option (e.g.
+.BR --auto=p7 ).
+If the device name ends with a digit, the partition names add an
+underscore, a 'p', and a number, e.g. "/dev/home1_p3". If there is no
+trailing digit, then the partition names just have a number added,
+e.g. "/dev/scratch3".
+
.SH For assemble:
.TP
.BR -m ", " --super-minor=
Minor number of device that array was created for. Devices which
don't have this minor number are excluded. If you create an array as
-/dev/md1, then all superblock will contain the minor number 1, even if
+/dev/md1, then all superblocks will contain the minor number 1, even if
the array is later assembled as /dev/md2.
-.TP
-.BR -c ", " --config=
-config file. Default is
-.BR /etc/mdadm.conf .
-
-.TP
-.BR -s ", " --scan
-scan config file for missing information
+Giving the literal word "dev" for
+.B --super-minor
+will cause
+.I mdadm
+to use the minor number of the md device that is being assembled.
+e.g. when assembling
+.BR /dev/md0 ,
+.M --super-minor=dev
+will look for super blocks with a minor number of 0.
.TP
.BR -f ", " --force
.B --run
an attempt will be made to start it anyway.
-.SH General management
+.TP
+.BR -a ", " "--auto{=no,yes,md,mdp,part}"
+See this option under Create and Build options.
+
+.TP
+.BR -U ", " --update=
+Update the superblock on each device while assembling the array. The
+argument given to this flag can be one of
+.BR sparc2.2 ,
+.BR summaries ,
+or
+.BR super-minor .
+
+The
+.B sparc2.2
+option will adjust the superblock of an array what was created on a Sparc
+machine running a patched 2.2 Linux kernel. This kernel got the
+alignment of part of the superblock wrong. You can use the
+.B "--examine --sparc2.2"
+option to
+.I mdadm
+to see what effect this would have.
+
+The
+.B super-minor
+option will update the
+.B "prefered minor"
+field on each superblock to match the minor number of the array being
+assembled. This is not needed on 2.6 and later kernels as they make
+this adjustment automatically.
+
+The
+.B summaries
+option will correct the summaries in the superblock. That is the
+counts of total, working, active, failed, and spare devices.
+
+.SH For Manage mode:
.TP
.BR -a ", " --add
.TP
.BR -r ", " --remove
-remove listed devices. The must not be active. i.e. they should
+remove listed devices. They must not be active. i.e. they should
be failed or spare devices.
.TP
.BR --set-faulty
same as --fail.
+.SH For Examine mode:
+
+.TP
+.B --sparc2.2
+In an array was created on a 2.2 Linux kernel patched with RAID
+support, the superblock will have been created incorrectly, or at
+least incompatibly with 2.4 and later kernels. Using the
+.B --sparc2.2
+flag with
+.B --examine
+will fix the superblock before displaying it. If this appears to do
+the right thing, then the array can be successfully assembled using
+.BR "--assemble --update=sparc2.2" .
+
+.SH For Misc mode:
+
.TP
.BR -R ", " --run
start a partially built array.
.BR -w ", " --readwrite
mark array as readwrite.
+.TP
+.B --zero-superblock
+If the device contains a valid md superblock, the block is
+over-written with zeros. With
+--force
+the block where the superblock would be is over-written even if it
+doesn't appear to be valid.
+
+.TP
+.BR -t ", " --test
+When used with
+.BR --detail ,
+the exit status of
+.I mdadm
+is set to reflect the status of the device.
+
+.SH For Monitor mode:
+.TP
+.BR -m ", " --mail
+Give a mail address to send alerts to.
+
+.TP
+.BR -p ", " --program ", " --alert
+Give a program to be run whenever an event is detected.
+
+.TP
+.BR -d ", " --delay
+Give a delay in seconds.
+.B mdadm
+polls the md arrays and then waits this many seconds before polling
+again. The default is 60 seconds.
+
+.TP
+.BR -f ", " --daemonise
+Tell
+.B mdadm
+to run as a background daemon if it decides to monitor anything. This
+causes it to fork and run in the child, and to disconnect form the
+terminal. The process id of the child is written to stdout.
+This is useful with
+.B --scan
+which will only continue monitoring if a mail address or alert program
+is found in the config file.
+
+.TP
+.BR -1 ", " --oneshot
+Check arrays only once. This will generate
+.B NewArray
+events and more significantly
+.B DegradedArray
+events. Running
+.in +5
+.B " mdadm --monitor --scan -1"
+.in -5
+from a cron script will ensure regular notification of any degraded arrays.
+
+.TP
+.BR -t ", " --test
+Generate a
+.B TestMessage
+alert for every array found at startup. This alert gets mailed and
+passed to the alert program. This can be used for testing that alert
+message to get through successfully.
-.SH ASSEMBLY MODE
+.SH ASSEMBLE MODE
.HP 12
Usage:
.B mdadm --assemble
-.I device options...
+.I md-device options-and-component-devices...
+.HP 12
+Usage:
+.B mdadm --assemble --scan
+.I md-devices-and-options...
.HP 12
Usage:
.B mdadm --assemble --scan
.PP
This usage assembles one or more raid arrays from pre-existing components.
For each array, mdadm needs to know the md device, the identity of the
-array, and a number of sub devices. These can be found in a number of ways.
+array, and a number of component-devices. These can be found in a number of ways.
+
+In the first usage example (without the
+.BR --scan )
+the first device given is the md device.
+In the second usage example, all devices listed are treated as md
+devices and assembly is attempted.
+In the third (where no devices are listed) all md devices that are
+listed in the configuration file are assembled.
-The md device is either given before
+If precisely one device is listed, but
.B --scan
-or is found from the config file. In the latter case, multiple md devices
-can be started with a single mdadm command.
+is not given, then
+.I mdadm
+acts as though
+.B --scan
+was given and identify information is extracted from the configuration file.
The identity can be given with the
.B --uuid
option, with the
.B --super-minor
-option, can be found in in the config file, or will be taken from the
-super block on the first subdevice listed on the command line.
+option, can be found in the config file, or will be taken from the
+super block on the first component-device listed on the command line.
Devices can be given on the
.B --assemble
-command line or from the config file. Only devices which have an md
-superblock which contains the right identity will be considered for any device.
+command line or in the config file. Only devices which have an md
+superblock which contains the right identity will be considered for
+any array.
The config file is only used if explicitly named with
.B --config
-or requested with
+or requested with (a possibly implicit)
.B --scan.
In the later case,
.B /etc/mdadm.conf
is not given, then the config file will only be used to find the
identity of md arrays.
-Normally the array will be started after it is assembled. However is
+Normally the array will be started after it is assembled. However if
.B --scan
-is not given and insufficient drives were lists to start a complete
+is not given and insufficient drives were listed to start a complete
(non-degraded) array, then the array is not started (to guard against
usage errors). To insist that the array be started in this case (as
-may work for RAID1 or RAID5), give the
+may work for RAID1, 4, 5 or 6), give the
.B --run
flag.
+If an
+.B auto
+option is given, either on the command line (--auto) or in the
+configuration file (e.g. auto=part), then
+.I mdadm
+will create the md device if necessary or will re-create it if it
+doesn't look usable as it is.
+
+This can be useful for handling partitioned devices (which don't have
+a stable device number - it can change after a reboot) and when using
+"udev" to manage your
+.B /dev
+tree (udev cannot handle md devices because of the unusual device
+initialisation conventions).
+
+If the option to "auto" is "mdp" or "part" or (on the command line
+only) "p", then mdadm will create a partitionable array, using the
+first free one that is not inuse, and does not already have an entry
+in /dev (apart from numeric /dev/md* entries).
+
+If the option to "auto" is "yes" or "md" or (on the command line)
+nothing, then mdadm will create a traditional, non-partitionable md
+array.
+
+It is expected that the "auto" functionality will be used to create
+device entries with meaningful names such as "/dev/md/home" or
+"/dev/md/root", rather than names based on the numerical array number.
+
+When using this option to create a partitionable array, the device
+files for the first 4 partitions are also created. If a different
+number is required it can be simply appended to the auto option.
+e.g. "auto=part8". Partition names are created by appending a digit
+string to the device name, with an intervening "_p" if the device name
+ends with a digit.
+
+The
+.B --auto
+option is also available in Build and Create modes. As those modes do
+not use a config file, the "auto=" config option does not apply to
+these modes.
.SH BUILD MODE
.I device
.BI --chunk= X
.BI --level= Y
-.BI --raid-disks= Z
+.BI --raid-devices= Z
.I devices
.PP
.BI --chunk= X
.BI --level= Y
.br
-.BI --raid-disks= Z
+.BI --raid-devices= Z
.I devices
.PP
This usage will initialise a new md array, associate some devices with
it, and activate the array.
+This the
+.B --auto
+option is given (as described in more detail in the section on
+Assemble mode), then the md device will be created with a suitable
+device number if necessary.
+
As devices are added, they are checked to see if they contain raid
-superblocks or filesystems. They are also check to see if the variance in
+superblocks or filesystems. They are also checked to see if the variance in
device size exceeds 1%.
If any discrepancy is found, the array will not automatically be run, though
.B --run
can override this caution.
+To create a "degraded" array in which some devices are missing, simply
+give the word "\fBmissing\fP"
+in place of a device name. This will cause
+.B mdadm
+to leave the corresponding slot in the array empty.
+For a RAID4 or RAID5 array at most one slot can be
+"\fBmissing\fP"; for a RAID6 array at most two slots.
+For a RAID1 array, only one real device needs to be given. All of the
+others can be
+"\fBmissing\fP".
+
+When creating a RAID5 array,
+.B mdadm
+will automatically create a degraded array with an extra spare drive.
+This is because building the spare into a degraded array is in general faster than resyncing
+the parity on a non-degraded, but not clean, array. This feature can
+be over-ridden with the
+-I --force
+option.
+
'''If the
'''.B --size
-'''option is given, it is not necessary to list any subdevices in this command.
+'''option is given, it is not necessary to list any component-devices in this command.
'''They can be added later, before a
'''.B --run.
'''If no
The General Management options that are valid with --create are:
.TP
.B --run
-insist of running the array even if some devices look like they might
+insist on running the array even if some devices look like they might
be in use.
.TP
.B --readonly
start the array readonly - not supported yet.
-.SH DETAIL MODE
+.SH MANAGE MODE
.HP 12
Usage:
-.B mdadm --detail
-.RB [ --brief ]
-.I device ...
+.B mdadm
+.I device
+.I options... devices...
.PP
-This usage sill print out the details of the given array including a
-list of component devices. To determine names for the devices,
+This usage will allow individual devices in an array to be failed,
+removed or added. It is possible to perform multiple operations with
+on command. For example:
+.br
+.B " mdadm /dev/md0 -f /dev/hda1 -r /dev/hda1 -a /dev/hda1"
+.br
+will firstly mark
+.B /dev/hda1
+as faulty in
+.B /dev/md0
+and will then remove it from the array and finally add it back
+in as a spare. However only one md array can be affected by a single
+command.
+
+.SH MISC MODE
+.HP 12
+Usage:
.B mdadm
-searches
-.B /dev
-for device files with the right major and minor numbers.
+.I options ...
+.I devices ...
+.PP
-With
+MISC mode includes a number if distinct operations that
+operate on distinct devices. The operations are:
+.TP
+--query
+The device is examined to see if it is
+(1) an active md array, or
+(2) a component of an md array.
+The information discovered is reported.
+
+.TP
+--detail
+The device should be an active md device.
+.B mdadm
+will display a detailed description of the array.
.B --brief
+or
+.B --scan
+will cause the output to be less detailed and the format to be
+suitable for inclusion in
+.BR /etc/mdadm.conf .
+The exit status of
+.I mdadm
+will normally be 0 unless
+.I mdadm
+failed to get useful information about the device(s). However if the
+.B --test
+option is given, then the exit status will be:
+.RS
+.TP
+0
+The array is functioning normally.
+.TP
+1
+The array has at least one failed device.
+.TP
+2
+The array has multiple failed devices and hence is unusable (raid4 or
+raid5).
+.TP
+4
+There was an error while trying to get information about the device.
+.RE
+
+.TP
+--examine
+The device should be a component of an md array.
.B mdadm
-prints a single line that identifies the level, number of disks, and
-UUID of the array. This line is suitable for inclusion in
+will read the md superblock of the device and display the contents.
+If
+.B --brief
+is given, or
+.B --scan
+then multiple devices that are components of the one array
+are grouped together and reported in a single entry suitable
+for inclusion in
.BR /etc/mdadm.conf .
-.SH EXAMINE MODE
+Having
+.B --scan
+without listing any devices will cause all devices listed in the
+config file to be examined.
+
+.TP
+--stop
+The devices should be active md arrays which will be deactivated, as
+long as they are not currently in use.
+
+.TP
+--run
+This will fully activate a partially assembled md array.
+
+.TP
+--readonly
+This will mark an active array as read-only, providing that it is
+not currently being used.
+
+.TP
+--readwrite
+This will change a
+.B readonly
+array back to being read/write.
+
+.TP
+--scan
+For all operations except
+.BR --examine ,
+.B --scan
+will cause the operation to be applied to all arrays listed in
+.BR /proc/mdstat .
+For
+.BR --examine,
+.B --scan
+causes all devices listed in the config file to be examined.
+
+
+.SH MONITOR MODE
+
.HP 12
Usage:
-.B mdadm --examine
-.RB [ --scan ]
-.RB [ --brief ]
-.I device ...
+.B mdadm --monitor
+.I options... devices...
+
.PP
-This usage will examine some block devices to see if that have a valid
-RAID superblock on them. The information in each valid raid
-superblock will be printed.
+This usage causes
+.B mdadm
+to periodically poll a number of md arrays and to report on any events
+noticed.
+.B mdadm
+will never exit once it decides that there are arrays to be checked,
+so it should normally be run in the background.
+
+As well as reporting events,
+.B mdadm
+may move a spare drive from one array to another if they are in the
+same
+.B spare-group
+and if the destination array has a failed drive but not spares.
+
+If any devices are listed on the command line,
+.B mdadm
+will only monitor those devices. Otherwise all arrays listed in the
+configuration file will be monitored. Further, if
+.B --scan
+is given, then any other md devices that appear in
+.B /proc/mdstat
+will also be monitored.
+
+The result of monitoring the arrays is the generation of events.
+These events are passed to a separate program (if specified) and may
+be mailed to a given E-mail address.
+
+When passing event to program, the program is run once for each event
+and is given 2 or 3 command-line arguements. The first is the
+name of the event (see below). The second is the name of the
+md device which is affected, and the third is the name of a related
+device if relevant, such as a component device that has failed.
If
.B --scan
-is used, the no devices should be listed, and the complete set of
-devices identified in the configuration file are checked.
+is given, then a program or an E-mail address must be specified on the
+command line or in the config file. If neither are available, then
+.B mdadm
+will not monitor anything.
+Without
.B --scan
-implies
-.B --brief
-but this implication can be countered by specifying
-.BR --verbose .
-
-With
-.B --brief
.B mdadm
-will output an config file entry of each distinct array that was
-found. This entry will list the UUID, the raid level, and a list of
-the individual devices on which a superblock for that array was found.
-This output will by syntactically suitable for inclusion in the
-configuration file, but should
-.B NOT
-be used blindly. Often the array description that you want in the
-configuration file is much less specific than that given by
-.BR "mdadm -Bs" .
-For example, you normally do not want to list the devices,
-particularly if they are SCSI devices.
-
-'''.SH BUGS
-'''no known bugs.
+will continue monitoring as long as something was found to monitor. If
+no program or email is given, then each event is reported to
+.BR stdout .
-.SH FILES
-
-.SS /proc/mdstat
+The different events are:
-If you're using the
-.B /proc
-filesystem,
-.B /proc/mdstat
-gives you informations about md devices status.
-This file is not currently used by
-.BR mdadm .
+.RS 4
+.TP
+.B DeviceDisappeared
+An md array which previously was configured appears to no longer be
+configured.
-.SS /etc/mdadm.conf
+.TP
+.B RebuildStarted
+An md array started reconstruction.
-The config file is line oriented with, as usual, blank lines and lines
-beginning with a hash (or pound sign or sharp or number sign,
-whichever you like to call it) ignored.
-Lines that start with a blank are treated as continuations of the
-previous line (I don't like trailing slashes).
+.TP
+.BI Rebuild NN
+Where
+.I NN
+is 20, 40, 60, or 80, this indicates that rebuild has passed that many
+percentage of the total.
-Each line contains a sequence of space-separated words, the first of
-which identified the type of line. Keywords are case-insensitive, and
-the first work on a line can be abbreviated to 3 letters.
+.TP
+.B RebuildFinished
+An md array that was rebuilding, isn't any more, either because it
+finished normally or was aborted.
-There are two types of lines. ARRAY and DEVICE.
+.TP
+.B Fail
+An active component device of an array has been marked as faulty.
-The DEVICE lines usually come first. All remaining words on the line
-are treated as names of devices, possibly containing wild cards (see
-.IR glob (7)).
-These list all the devices that
-.B mdadm
-is allowed to scan
-when looking for devices with RAID superblocks.
-Each line can contain multiple device names, and there can be multiple
-DEVICE lines. For example:
-.IP
-DEVICE /dev/hda* /dev/hdc*
-.br
-DEV /dev/sd*
-.br
-DEVICE /dev/discs/disc*/disc
-.PP
-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. If multiple identities are given,
-then the array much match ALL identities to be considered a match.
-Each identity word has a tag, and equals sign, and some value.
-The options are:
+.TP
+.B FailSpare
+A spare component device which was being rebuilt to replace a faulty
+device has failed.
.TP
-.B 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.
+.B SpareActive
+A spare component device which was being rebuilt to replace a faulty
+device as been successfully rebuild and has been made active.
+
.TP
-.B 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.
+.B NewArray
+A new md array has been detected in the
+.B /proc/mdstat
+file.
+
.TP
-.B devices=
-The value is a comma separated list of device names. Precisely these
-devices will be used to assemble the array. Note that the devices
-listed there must also be listed on a DEVICE line.
+.B DegradedArray
+A newly noticed array appears to be degraded. This message is not
+generated when
+.I mdadm
+notices a drive failure which causes degradation, but only when
+.I mdadm
+notices that an array is degraded when it first sees the array.
+
.TP
-.B level=
-The value is a raid level. This is normally used to identify an
-array, but is supported so that the output of
-.B "mdadm --examine --scan"
-can be use directly in the configuration file.
+.B MoveSpare
+A spare drive has been moved from one array in a
+.B spare-group
+to another to allow a failed drive to be replaced.
+
.TP
-.B disks=
-The value is the number of disks in a complete active array. As with
-.B level=
-this is mainly for compatibility with the output of
-.BR "mdadm --examine --scan" .
+.B TestMessage
+An array was found at startup, and the
+.B --test
+flag was given.
+.RE
+
+Only
+.B Fail ,
+.B FailSpare ,
+.B DegradedArray ,
+and
+.B TestMessage
+cause Email to be sent. All events cause the program to be run.
+The program is run with two or three arguments, they being the event
+name, the array device and possibly a second device.
+
+Each event has an associated array device (e.g.
+.BR /dev/md1 )
+and possibly a second device. For
+.BR Fail ,
+.BR FailSpare ,
+and
+.B SpareActive
+the second device is the relevant component device.
+For
+.B MoveSpare
+the second device is the array that the spare was moved from.
+
+For
+.B mdadm
+to move spares from one array to another, the different arrays need to
+be labelled with the same
+.B spare-group
+in the configuration file. The
+.B spare-group
+name can be any string. It is only necessary that different spare
+groups use different names.
+
+When
+.B mdadm
+detects that an array which is in a spare group has fewer active
+devices than necessary for the complete array, and has no spare
+devices, it will look for another array in the same spare group that
+has a full complement of working drive and a spare. It will then
+attempt to remove the spare from the second drive and add it to the
+first.
+If the removal succeeds but the adding fails, then it is added back to
+the original array.
+
+.SH GROW MODE
+The GROW mode is used for changing the size or shape of an active
+array.
+For this to work, the kernel must support the necessary change.
+Various types of growth may be added during 2.6 development, possibly
+including restructuring a raid5 array to have more active devices.
+
+Currently the only support available is to change the "size" attribute
+for arrays with redundancy, and the raid-disks attribute of RAID1
+arrays.
+
+Normally when an array is build the "size" it taken from the smallest
+of the drives. If all the small drives in an arrays are, one at a
+time, removed and replaced with larger drives, then you could have an
+array of large drives with only a small amount used. In this
+situation, changing the "size" with "GROW" mode will allow the extra
+space to start being used. If the size is increased in this way, a
+"resync" process will start to make sure the new parts of the array
+are synchronised.
+
+Note that when an array changes size, any filesystem that may be
+stored in the array will not automatically grow to use the space. The
+filesystem will need to be explicitly told to use the extra space.
+
+A RAID1 array can work with any number of devices from 1 upwards
+(though 1 is not very useful). There may be times which you want to
+increase or decrease the number of active devices. Note that this is
+different to hot-add or hot-remove which changes the number of
+inactive devices.
+
+When reducing the number of devices in a RAID1 array, the slots which
+are to be removed from the array must already be vacant. That is, the
+devices that which were in those slots must be failed and removed.
+
+When the number of devices is increased, any hot spares that are
+present may be activated immediately.
+
+.SH EXAMPLES
+
+.B " mdadm --query /dev/name-of-device"
+.br
+This will find out if a given device is a raid array, or is part of
+one, and will provide brief information about the device.
+
+.B " mdadm --assemble --scan"
+.br
+This will assemble and start all arrays listed in the standard confile
+file. This command will typically go in a system startup file.
+
+.B " mdadm --stop --scan"
+.br
+This will shut down all array that can be shut down (i.e. are not
+currently in used). This will typically going in a system shutdown script.
+
+.B " mdadm --follow --scan --delay=120"
+.br
+If (and only if) there is an Email address or program given in the
+standard config file, then
+monitor the status of all arrays listed in that file by
+polling them ever 2 minutes.
+
+.B " mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hd[ac]1"
+.br
+Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
+
+.br
+.B " echo 'DEVICE /dev/hd*[0-9] /dev/sd*[0-9]' > mdadm.conf"
+.br
+.B " mdadm --detail --scan >> mdadm.conf"
+.br
+This will create a prototype config file that describes currently
+active arrays that are known to be made from partitions of IDE or SCSI drives.
+This file should be reviewed before being used as it may
+contain unwanted detail.
+
+.B " echo 'DEVICE /dev/hd[a-z] /dev/sd*[a-z]' > mdadm.conf"
+.br
+.B " mdadm --examine --scan --config=mdadm.conf >> mdadm.conf"
+.ber
+This will find what arrays could be assembled from existign IDE and
+SCSI whole drives (not partitions) and store the information is the
+format of a config file.
+This file is very likely to contain unwanted detail, particularly
+the
+.B devices=
+entries. It should be reviewed and edited before being used as an
+actual config file.
+
+.B " mdadm --examine --brief --scan --config=partitions"
+.br
+.B " mdadm -Ebsc partitions"
+.br
+Create a list of devices by reading
+.BR /proc/partitions ,
+scan these for RAID superblocks, and printout a brief listing of all
+that was found.
-.SH TODO
+.B " mdadm -Ac partitions -m 0 /dev/md0"
+.br
+Scan all partitions and devices listed in
+.BR /proc/partitions
+and assemble
+.B /dev/md0
+out of all such devices with a RAID superblock with a minor number of 0.
+
+.B " mdadm --monitor --scan --daemonise > /var/run/mdadm"
+.br
+If config file contains a mail address or alert program, run mdadm in
+the background in monitor mode monitoring all md devices. Also write
+pid of mdadm daemon to
+.BR /var/run/mdadm .
+
+.B " mdadm --create --help"
+.br
+Providew help about the Create mode.
+
+.B " mdadm --config --help"
+.br
+Provide help about the format of the config file.
-Finish and document Follow mode.
+.B " mdadm --help"
+.br
+Provide general help.
+
+
+.SH FILES
+.SS /proc/mdstat
+
+If you're using the
+.B /proc
+filesystem,
+.B /proc/mdstat
+lists all active md devices with information about them.
+.B mdadm
+uses this to find arrays when
+.B --scan
+is given in Misc mode, and to monitor array reconstruction
+on Monitor mode.
+
+
+.SS /etc/mdadm.conf
+
+The config file lists which devices may be scanned to see if
+they contain MD super block, and gives identifying information
+(e.g. UUID) about known MD arrays. See
+.BR mdadm.conf (5)
+for more details.
+
+
+.SH NOTE
+.B mdadm
+was previously known as
+.BR mdctl .
+
.SH SEE ALSO
For information on the various levels of
RAID, check out:
http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
.URk
.PP
+.BR mdadm.conf (5),
+.BR md (4).
+.PP
.IR raidtab (5),
.IR raid0run (8),
.IR raidstop (8),
projects / thirdparty / mdadm.git / blobdiff