.\" the Free Software Foundation; either version 2 of the License, or
.\" (at your option) any later version.
.\" See file COPYING in distribution for details.
-.TH MDADM 8 "" v2.6.4
+.TH MDADM 8 "" v3.0-devel3
.SH NAME
mdadm \- manage MD devices
.I aka
.BR RAID6 ,
.BR RAID10 ,
.BR MULTIPATH ,
+.BR FAULTY ,
and
-.BR FAULTY .
+.BR CONTAINER .
.B MULTIPATH
is not a Software RAID mechanism, but does involve
is also not true RAID, and it only involves one device. It
provides a layer over a true device that can be used to inject faults.
-.\".B mdadm
+.B CONTAINER
+is different again. A
+.B CONTAINER
+is a collection of devices that are
+managed as a set. This is similar to the set of devices connected to
+a hardware RAID controller. The set of devices may contain a number
+of different RAID arrays each utilising some (or all) blocks from a
+number of the devices in the set. For example, two devices in a 5-device set
+might form a RAID1 used the whole devices. The remaining three might
+have a RAID5 over the first half of each device, and a RAID0 over the
+second half.
+
+With a
+.BR CONTAINER ,
+there is one set of metadata that describes all of
+the arrays in the container. So when
+.I mdadm
+creates a
+.B CONTAINER
+device, it just represents the metadata. Other normal arrays (RAID1
+etc) can be created inside that container.
+
+
+.\".I mdadm
.\"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.
.\"The key differences between
-.\".B mdadm
+.\".I mdadm
.\"and
.\".B raidtools
.\"are:
.\".IP \(bu 4
-.\".B mdadm
+.\".I mdadm
.\"is a single program and not a collection of programs.
.\".IP \(bu 4
-.\".B mdadm
+.\".I mdadm
.\"can perform (almost) all of its functions without having a
.\"configuration file and does not use one by default. Also
-.\".B mdadm
+.\".I mdadm
.\"helps with management of the configuration
.\"file.
.\".IP \(bu 4
-.\".B mdadm
+.\".I mdadm
.\"can provide information about your arrays (through Query, Detail, and Examine)
.\"that
.\".B raidtools
Assemble the components of a previously created
array into an active array. Components can be explicitly given
or can be searched for.
-.B mdadm
+.I mdadm
checks that the components
do form a bona fide array, and can, on request, fiddle superblock
information so as to assemble a faulty array.
system. As each device is detected,
.I mdadm
has a chance to include it in some array as appropriate.
+.P
+If a
+.B CONTAINER
+is passed to
+.I mdadm
+in this mode, then any arrays within that container will be assembled
+and started.
.TP
.B Manage
.TP
.BR \-q ", " \-\-quiet
Avoid printing purely informative messages. With this,
-.B mdadm
+.I mdadm
will be silent unless there is something really important to report.
.TP
then nothing will be read, but
.I mdadm
will act as though the config file contained exactly
-.B "DEVICE partitions"
+.B "DEVICE partitions containers"
and will read
.B /proc/partitions
-to find a list of devices to scan.
+to find a list of devices to scan, and
+.B /proc/mdstat
+to find a list of containers to examine.
If the word
.B "none"
is given for the config file, then
.B /proc/mdstat
for missing information.
In general, this option gives
-.B mdadm
+.I mdadm
permission to get any missing information (like component devices,
array devices, array identities, and alert destination) from the
configuration file (see previous option);
The different sub-versions store the superblock at different locations
on the device, either at the end (for 1.0), at the start (for 1.1) or
4K from the start (for 1.2).
+.IP ddf
+Use the "Industry Standard" DDF (Disk Data Format) format. When
+creating a DDF array a
+.B CONTAINER
+will be created, and normal arrays can be created in that container.
+.IP imsm
+Use the Intel(R) Matrix Storage Manager metadata format. This creates a
+.B CONTAINER
+which is managed in a similar manner to DDF, and is supported by an
+option-rom on some platforms:
+.IP
+.B http://www.intel.com/design/chipsets/matrixstorage_sb.htm
+.PP
.RE
.TP
.B max
which means to choose the largest size that fits on all current drives.
+This value can not be used with
+.B CONTAINER
+metadata such as DDF and IMSM.
+
.TP
.BR \-c ", " \-\-chunk=
Specify chunk size of kibibytes. The default is 64.
Set raid level. When used with
.BR \-\-create ,
options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
-raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty. Obviously some of these are synonymous.
+raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container.
+Obviously some of these are synonymous.
+
+When a
+.B CONTAINER
+metadata type is requested, only the
+.B container
+level is permitted, and it does not need to be explicitly given.
When used with
.BR \-\-build ,
end of this option (e.g.
.BR \-\-auto=p7 ).
If the device name ends with a digit, the partition names add a 'p',
-and a number, e.g. "/dev/home1p3". If there is no
+and a number, e.g. "/dev/md/home1p3". If there is no
trailing digit, then the partition names just have a number added,
-e.g. "/dev/scratch3".
+e.g. "/dev/md/scratch3".
If the md device name is in a 'standard' format as described in DEVICE
NAMES, then it will be created, if necessary, with the appropriate
formats, then a unused minor number will be allocated. The minor
number will be considered unused if there is no active array for that
number, and there is no entry in /dev for that number and with a
-non-standard name.
-
-.TP
-.BR \-\-symlink = no
-Normally when
-.B \-\-auto
-causes
-.I mdadm
-to create devices in
-.B /dev/md/
-it will also create symlinks from
-.B /dev/
-with names starting with
-.B md
-or
-.BR md_ .
-Use
-.B \-\-symlink=no
-to suppress this, or
-.B \-\-symlink=yes
-to enforce this even if it is suppressing
-.IR mdadm.conf .
-
+non-standard name. Name that are not in 'standard' format are only
+allowed in "/dev/md/".
+
+\".TP
+\".BR \-\-symlink = no
+\"Normally when
+\".B \-\-auto
+\"causes
+\".I mdadm
+\"to create devices in
+\".B /dev/md/
+\"it will also create symlinks from
+\".B /dev/
+\"with names starting with
+\".B md
+\"or
+\".BR md_ .
+\"Use
+\".B \-\-symlink=no
+\"to suppress this, or
+\".B \-\-symlink=yes
+\"to enforce this even if it is suppressing
+\".IR mdadm.conf .
+\"
.SH For assemble:
to use the minor number of the md device that is being assembled.
e.g. when assembling
.BR /dev/md0 ,
-.M \-\-super\-minor=dev
+.B \-\-super\-minor=dev
will look for super blocks with a minor number of 0.
.TP
same as
.BR \-\-fail .
+.TP
+.BR \-\-write\-mostly
+Subsequent devices that are added or re-added will have the 'write-mostly'
+flag set. This is only valid for RAID! and means that the 'md' driver
+will avoid reading from these devices if possible.
+.TP
+.BR \-\-readwrite
+Subsequent devices that are added or re-added will have the 'write-mostly'
+flag cleared.
+
+
.P
Each of these options require that the first device listed is the array
to be acted upon, and the remainder are component devices to be added,
.BR \-D ", " \-\-detail
Print detail of one or more md devices.
+.TP
+.BR \-\-detail\-platform
+Print detail of the platform's raid capabilities (firmware / hardware
+topology) for a given metadata format.
+
.TP
.BR \-Y ", " \-\-export
When used with
will return with success if it actually waited for every device
listed, otherwise it will return failure.
+.TP
+.BR \-\-wait\-clean
+For each md device given, or each device in /proc/mdstat if
+.B \-\-scan
+is given, arrange for the array to be marked clean as soon as possible.
+Also, quiesce resync so that the monitor for external metadata arrays
+(mdmon) has an opportunity to checkpoint the resync position.
+.I mdadm
+will return with success if the array uses external metadata and we
+successfully waited. For native arrays this returns immediately as the
+kernel handles both dirty-clean transitions and resync checkpointing in
+the kernel at shutdown. No action is taken if safe-mode handling is
+disabled.
+
.SH For Incremental Assembly mode:
.TP
.BR \-\-rebuild\-map ", " \-r
Run any array assembled as soon as a minimal number of devices are
available, rather than waiting until all expected devices are present.
+.TP
+.B \-\-no\-degraded
+This allows the hot-plug system to prevent arrays from running when it knows
+that more disks may arrive later in the discovery process.
+
.TP
.BR \-\-scan ", " \-s
Only meaningful with
.TP
.BR \-d ", " \-\-delay
Give a delay in seconds.
-.B mdadm
+.I 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
+.I 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.
.TP
.BR \-i ", " \-\-pid\-file
When
-.B mdadm
+.I mdadm
is running in daemon mode, write the pid of the daemon process to
the specified file, instead of printing it on standard output.
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.
+listed in the configuration file are assembled. Then any arrays that
+can be found on unused devices will also be assembled.
If precisely one device is listed, but
.B \-\-scan
.BR \-\-scan .
In the later case,
.B /etc/mdadm.conf
+or
+.B /etc/mdadm/mdadm.conf
is used.
If
will first attempt to assemble all the arrays listed in the config
file.
-If a
-.B homehost
-has been specified (either in the config file or on the command line),
-.I mdadm
-will look further for possible arrays and will try to assemble
-anything that it finds which is tagged as belonging to the given
-homehost. This is the only situation where
-.I mdadm
-will assemble arrays without being given specific device name or
-identity information for the array.
+It will then look further for possible arrays and will try to assemble
+anything that it finds. Arrays which are tagged as belonging to the given
+homehost will be assembled and started normally. Arrays which do not
+obviously belong to this host are given names that are expected not to
+conflict with anything local, and are started "read-auto" so that
+nothing is written to any device until the array is written to. i.e.
+automatic resync etc is delayed.
If
.I mdadm
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
+.I 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.
"\fBmissing\fP".
When creating a RAID5 array,
-.B mdadm
+.I 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
.B \-\-force
option.
-When creating an array with version-1 metadata a name for the host is
+When creating an array with version-1 metadata a name for the array is
required.
If this is not given with the
.B \-\-name
option,
.I mdadm
-will chose a name based on the last component of the name of the
+will choose a name based on the last component of the name of the
device being created. So if
.B /dev/md3
is being created, then the name
.B home
will be used.
+When creating a partition based array, using
+.I mdadm
+with version-1.x metadata, the partition type should be set to
+.B 0xDA
+(non fs-data). This type selection allows for greater precision since
+using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
+might create problems in the event of array recovery through a live cdrom.
+
A new array will normally get a randomly assigned 128bit UUID which is
very likely to be unique. If you have a specific need, you can choose
a UUID for the array by giving the
.\".B \-\-size
.\"is given, the apparent size of the smallest drive given is used.
+When creating an array within a
+.B CONTAINER
+.I mdadm
+can be given either the list of devices to use, or simply the name of
+the container. The former case gives control over which devices in
+the container will be used for the array. The latter case allows
+.I mdadm
+to automatically choose which devices to use based on how much spare
+space is available.
+
The General Management options that are valid with
.B \-\-create
are:
There was an error while trying to get information about the device.
.RE
+.TP
+.B \-\-detail\-platform
+Print detail of the platform's raid capabilities (firmware / hardware
+topology). If the metadata is specified with
+.B \-e
+or
+.B \-\-metadata=
+then the return status will be:
+.RS
+.TP
+0
+metadata successfully enumerated its platform components on this system
+.TP
+1
+metadata is platform independent
+.TP
+2
+metadata failed to find its platform components on this system
+.RE
+
.TP
.B \-\-examine
The device should be a component of an md array.
-.B mdadm
+.I mdadm
will read the md superblock of the device and display the contents.
If
.B \-\-brief
.PP
This usage causes
-.B mdadm
+.I mdadm
to periodically poll a number of md arrays and to report on any events
noticed.
-.B mdadm
+.I 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
+.I 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 no spares.
If any devices are listed on the command line,
-.B mdadm
+.I mdadm
will only monitor those devices. Otherwise all arrays listed in the
configuration file will be monitored. Further, if
.B \-\-scan
.B \-\-scan
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
+.I mdadm
will not monitor anything.
Without
.B \-\-scan,
-.B mdadm
+.I mdadm
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 .
the second device is the array that the spare was moved from.
For
-.B mdadm
+.I mdadm
to move spares from one array to another, the different arrays need to
be labeled with the same
.B spare-group
groups use different names.
When
-.B mdadm
+.I mdadm
detects that an array 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
change the "size" attribute
for RAID1, RAID5 and RAID6.
.IP \(bu 4
-increase the "raid-disks" attribute of RAID1, RAID5, and RAID6.
+increase the "raid\-devices" attribute of RAID1, RAID5, and RAID6.
.IP \(bu 4
add a write-intent bitmap to any array which supports these bitmaps, or
remove a write-intent bitmap from such an array.
.PP
+GROW mode is not currently supported for
+.B CONTAINERS
+or arrays inside containers.
+
.SS SIZE CHANGES
Normally when an array is built the "size" it taken from the smallest
of the drives. If all the small drives in an arrays are, one at a
.B "mdadm \-\-incremental"
to be conditionally added to an appropriate array.
+If the device passed is a
+.B CONTAINER
+device created by a previous call to
+.IR mdadm ,
+then rather than trying to add that device to an array, all the arrays
+described by the metadata of the container will be started.
+
.I mdadm
performs a number of tests to determine if the device is part of an
array, and which array it should be part of. If an appropriate array
(active or spare) parts of that array. It does not currently support
automatic inclusion of a new drive as a spare in some array.
-.B "mdadm \-\-incremental"
-requires a bug-fix in all kernels through 2.6.19.
-Hopefully, this will be fixed in 2.6.20; alternately, apply the patch
-which is included with the mdadm source distribution. If
-.I mdadm
-detects that this bug is present, it will abort any attempt to use
-.BR \-\-incremental .
-
The tests that
.I mdadm
makes are as follow:
As an alternative,
.B \-\-run
may be passed to
-.B mdadm
+.I mdadm
in which case the array will be run as soon as there are enough
devices present for the data to be accessible. For a raid1, that
means one device will start the array. For a clean raid5, the array
happens. Further devices that are found before the first write can
still be added safely.
+
+.SH ENVIRONMENT
+This section describes environment variables that affect how mdadm
+operates.
+
+.TP
+.B MDADM_NO_MDMON
+Setting this value to 1 will prevent mdadm from automatically launching
+mdmon. This variable is intended primarily for debugging mdadm/mdmon.
+
+.TP
+.B MDADM_NO_UDEV
+Normally,
+.I mdadm
+does not create any device nodes in /dev, but leaves that task to
+.IR udev .
+If
+.I udev
+appears not to be configured, or if this environment variable is set
+to '1', the
+.I mdadm
+will create and devices that are needed.
+
.SH EXAMPLES
.B " mdadm \-\-query /dev/name-of-device"
Any devices which are components of /dev/md4 will be marked as faulty
and then remove from the array.
+.B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
+.br
+Create a DDF array over 6 devices.
+
+.B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
+.br
+Create a raid5 array over any 3 devices in the given DDF set. Use
+only 30 gigabytes of each device.
+
+.B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
+.br
+Assemble a pre-exist ddf array.
+
+.B " mdadm -I /dev/md/ddf1"
+.br
+Assemble all arrays contained in the ddf array, assigning names as
+appropriate.
+
.B " mdadm \-\-create \-\-help"
.br
Provide help about the Create mode.
filesystem,
.B /proc/mdstat
lists all active md devices with information about them.
-.B mdadm
+.I mdadm
uses this to find arrays when
.B \-\-scan
is given in Misc mode, and to monitor array reconstruction
.SH DEVICE NAMES
-While entries in the /dev directory can have any format you like,
.I mdadm
-has an understanding of 'standard' formats which it uses to guide its
-behaviour when creating device files via the
-.B \-\-auto
-option.
+understand two sorts of names for array devices.
+
+The first is the so-called 'standard' format name, which matches the
+names used by the kernel and which appear in
+.IR /proc/mdstat .
+
+The second sort can be freely chosen, but must reside in
+.IR /dev/md/ .
+When giving a device name to
+.I mdadm
+to create or assemble an array, either full path name such as
+.I /dev/md0
+or
+.I /dev/md/home
+can be given, or just the suffix of the second sort of name, such as
+.I home
+can be given.
+
+When
+.I mdadm
+chooses device names during auto-assembly, it will normally add a
+small sequence number to the end of the name to avoid conflicted
+between multiple arrays that have the same name. If
+.I mdadm
+can reasonably determine that the array really is meant for this host,
+either by a hostname in the metadata, or by the presence of the array
+in /etc/mdadm.conf, then it will leave of the suffix if possible.
The standard names for non-partitioned arrays (the only sort of md
-array available in 2.4 and earlier) are either of
+array available in 2.4 and earlier) are of the form
.IP
/dev/mdNN
-.br
-/dev/md/NN
.PP
where NN is a number.
The standard names for partitionable arrays (as available from 2.6
-onwards) are either of
+onwards) are of the form
.IP
-/dev/md/dNN
-.br
/dev/md_dNN
.PP
Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2".
+.PP
+From kernel version, 2.6.28 the "non-partitioned array" can actually
+be partitioned. So the "md_dNN" names are no longer needed, and
+partitions such as "/dev/mdNNpXX" are possible.
.SH NOTE
-.B mdadm
+.I mdadm
was previously known as
-.BR mdctl .
+.IR mdctl .
.P
-.B mdadm
+.I mdadm
is completely separate from the
-.B raidtools
+.I raidtools
package, and does not use the
.I /etc/raidtab
configuration file at all.
.SH SEE ALSO
-For further information on MD and the various levels of
+For further information on mdadm usage, MD and the various levels of
RAID, see:
-
-.IP
-.UR http://unthought.net/Software-RAID.HOWTO/
-http://unthought.net/Software\-RAID.HOWTO/
-.UE
.IP
-.UR http://linux-raid.osdl.org/
-http://linux\-raid.osdl.org/
-.UE
+.B http://linux\-raid.osdl.org/
+.PP
+(based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
.\".PP
.\"for new releases of the RAID driver check out:
.\"
.I mdadm
should always be available from
.IP
-.UR http://www.kernel.org/pub/linux/utils/raid/mdadm/
-http://www.kernel.org/pub/linux/utils/raid/mdadm/
-.UE
+.B http://www.kernel.org/pub/linux/utils/raid/mdadm/
+.PP
+Related man pages:
.PP
.IR mdadm.conf (5),
.IR md (4).
projects / thirdparty / mdadm.git / blobdiff