mdadm-1.5.0

[thirdparty/mdadm.git] / mdadm.8

diff --git a/mdadm.8 b/mdadm.8
index 7eba10ca1dc698ea4db717ddb896a0c41c2c26ae..38bcb7377d5d401ec8e005a6642528f8e6f75495 100644 (file)
--- a/mdadm.8
+++ b/mdadm.8
@@ -1,5 +1,5 @@
 .\" -*- nroff -*-
 .\" -*- nroff -*-

-.TH mdadm 8
+.TH MDADM 8 "" v1.5.0

 .SH NAME
 mdadm \- manage MD devices
 .I aka
 .SH NAME
 mdadm \- manage MD devices
 .I aka


@@ -7,17 +7,18 @@ Linux Software Raid.
 
 .SH SYNOPSIS
 
 
 .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.
 
 .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.
 
 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
 
 Currently, Linux supports
 .B LINEAR


@@ -26,17 +27,21 @@ md devices,
 (striping),
 .B RAID1
 (mirroring),
 (striping),
 .B RAID1
 (mirroring),

-.B RAID4
+.BR RAID4 ,
+.BR RAID5 ,
+.BR RAID6 ,

 and
 and

-.B RAID5.
-
-Recent kernels (2002) also support a mode known as

 .BR MULTIPATH .
 .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
 
 .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.
 such it provides a similar set of functionality to the
 .B raidtools
 packages.


@@ -51,22 +56,27 @@ is a single program and not a collection of programs.
 .IP \(bu 4
 .B mdadm
 can perform (almost) all of its functions without having a
 .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
 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.
 that
 .B  raidtools
 cannot.

-.IP \(bu 4
+.P
+.I mdadm
+does not use
+.IR /etc/raidtab ,
+the

 .B raidtools
 .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
 
 .SH MODES

-mdadm has 7 major modes of operation:
+mdadm has 6 major modes of operation:

 .TP
 .B Assemble
 Assemble the parts of a previously created
 .TP
 .B Assemble
 Assemble the parts of a previously created


@@ -88,31 +98,22 @@ Create a new array with per-device superblocks.
 '''in several step create-add-add-run or it can all happen with one command.
 
 .TP
 '''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
 
 .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"
 
 .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.

 
 .SH OPTIONS
 
 
 .SH OPTIONS
 


@@ -120,7 +121,7 @@ Available options are:
 
 .TP
 .BR -A ", " --assemble
 
 .TP
 .BR -A ", " --assemble

-Assemble an existing array.
+Assemble a pre-existing array.

 
 .TP
 .BR -B ", " --build
 
 .TP
 .BR -B ", " --build


@@ -130,6 +131,13 @@ Build a legacy array without superblocks.
 .BR -C ", " --create
 Create a new array.
 
 .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.
 .TP
 .BR -D ", " --detail
 Print detail of one or more md devices.


@@ -146,7 +154,13 @@ mode.
 
 .TP
 .BR -h ", " --help
 
 .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
 
 .TP
 .BR -V ", " --version


@@ -163,6 +177,50 @@ Be less verbose.  This is used with
 and
 .BR --examine .
 
 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
 .SH For create or build:
 
 .TP


@@ -175,31 +233,54 @@ Specify rounding factor for linear array (==chunk size)
 
 .TP
 .BR -l ", " --level=
 
 .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:
 
 .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
 
 .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.  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
+Note that this number cannot be changed once the array has been created.

 
 .TP
 
 .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=
 
 .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
 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


@@ -218,17 +299,18 @@ excluded
 .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
 .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.
 
 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
 
 .TP
 .BR -f ", " --force


@@ -244,7 +326,39 @@ With
 .B --run
 an attempt will be made to start it anyway.
 
 .B --run
 an attempt will be made to start it anyway.
 

-.SH General management
+.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 -a ", " --add


@@ -253,7 +367,7 @@ hotadd listed devices.
 
 .TP
 .BR -r ", " --remove
 
 .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
 be failed or spare devices.
 
 .TP


@@ -264,6 +378,22 @@ mark listed devices as faulty.
 .BR --set-faulty
 same as --fail.
 
 .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.
 .TP
 .BR -R ", " --run
 start a partially built array.


@@ -280,13 +410,80 @@ mark array as readonly.
 .BR -w ", " --readwrite
 mark array as readwrite.
 
 .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.

 
 

-.SH ASSEMBLY MODE
+.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 ASSEMBLE MODE

 
 .HP 12
 Usage:
 .B mdadm --assemble
 
 .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
 .HP 12
 Usage:
 .B mdadm --assemble --scan


@@ -295,28 +492,40 @@ Usage:
 .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
 .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
+is not given, that
+.I mdadm
+acts as though

 .B --scan
 .B --scan

-or is found from the config file. In the latter case, multiple md devices
-can be started with a single mdadm command.
+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
 
 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
 
 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
 
 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
 .B --scan. 
 In the later case,
 .B /etc/mdadm.conf


@@ -327,12 +536,12 @@ If
 is not given, then the config file will only be used to find the
 identity of md arrays.
 
 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
 .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
 (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.
 
 .B --run
 flag.
 


@@ -345,7 +554,7 @@ Usage:
 .I device
 .BI --chunk= X
 .BI --level= Y
 .I device
 .BI --chunk= X
 .BI --level= Y

-.BI --raid-disks= Z
+.BI --raid-devices= Z

 .I devices
 
 .PP
 .I devices
 
 .PP


@@ -368,7 +577,7 @@ Usage:
 .BI --chunk= X
 .BI --level= Y
 .br
 .BI --chunk= X
 .BI --level= Y
 .br

-.BI --raid-disks= Z
+.BI --raid-devices= Z

 .I  devices
 
 .PP
 .I  devices
 
 .PP


@@ -376,7 +585,7 @@ This usage will initialise a new md array, associate some devices with
 it, and activate the array.
 
 As devices are added, they are checked to see if they contain raid
 it, and activate the array.
 
 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
 device size exceeds 1%.
 
 If any discrepancy is found, the array will not automatically be run, though


@@ -384,9 +593,29 @@ the presence of a
 .B --run
 can override this caution.
 
 .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
 '''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 
 '''They can be added later, before a
 '''.B --run. 
 '''If no 


@@ -403,150 +632,413 @@ be in use.
 .B --readonly
 start the array readonly - not supported yet.
 
 .B --readonly
 start the array readonly - not supported yet.
 

-.SH DETAIL MODE
+.SH MANAGE MODE

 .HP 12
 Usage:
 .HP 12
 Usage:

-.B mdadm --detail
-.RB [ --brief ]
-.I device ...
+.B mdadm
+.I device
+.I options... devices...

 .PP
 
 .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
 .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
 .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
 .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 .
 
 .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:
 .HP 12
 Usage:

-.B mdadm --examine
-.RB [ --scan ]
-.RB [ --brief ]
-.I device ...
+.B mdadm --monitor
+.I options... devices...
+

 .PP
 .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
 
 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
 .B --scan

-implies
-.B --brief
-but this implication can be countered by specifying
-.BR --verbose .
-
-With
-.B --brief

 .B mdadm
 .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
+The different events are:

 
 

-.SS /proc/mdstat
-
-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
 
 .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
 .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
 .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
 .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
 .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 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.
+
+.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.

 
 

-.SH TODO
+.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.
+
+.B "  mdadm --help"
+.br
+Provide general help.

 
 

-Finish and document Follow mode.

 
 

+.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:
 .SH SEE ALSO
 For information on the various levels of
 RAID, check out:


@@ -569,6 +1061,9 @@ or
 http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
 .URk
 .PP
 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),
 .IR raidtab (5),
 .IR raid0run (8),
 .IR raidstop (8),