A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
-bash/zsh: mdadm command not not found # Windows (WSL2) sudo apt-get update sudo apt-get install mdadm # Debian apt-get install mdadm # Ubuntu apt-get install mdadm # Alpine apk add mdadm # Arch Linux pacman -S mdadm # Kali Linux apt-get install mdadm # CentOS yum install mdadm # Fedora dnf install mdadm # Raspbian apt-get install mdadm # Dockerfile dockerfile.run/mdadm # Docker docker run cmd.cat/mdadm mdadm
mdadm 取代了之前所有用于管理 RAID 阵列的工具。它几乎管理 RAID 的所有用户空间部分。虽然有一些操作需要通过写入 /proc 文件系统来完成，但操作并不多。mdadm 有七种模式。
mdadm [mode] <raiddevice> [options] <component-devices>
mdadm [mode] <raiddevice> [options] <component-devices>
mdadm has several major modes of operation:
Assemble
Assemble the components of a previously created array into an
active array. Components can be explicitly given or can be
searched for. 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.
Build Build an array that doesn't have per-device metadata
(superblocks). For these sorts of arrays, mdadm cannot
differentiate between initial creation and subsequent assembly of
an array. It also cannot perform any checks that appropriate
components have been requested. Because of this, the Build mode
should only be used together with a complete understanding of what
you are doing.
Create Create a new array with per-device metadata (superblocks).
Appropriate metadata is written to each device, and then the array
comprising those devices is activated. A 'resync' process is
started to make sure that the array is consistent (e.g. both sides
of a mirror contain the same data) but the content of the device
is left otherwise untouched. The array can be used as soon as it
has been created. There is no need to wait for the initial resync
to finish.
Follow or Monitor
Monitor one or more md devices and act on any state changes. This
is only meaningful for RAID1, 4, 5, 6, 10 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.
Grow Grow (or shrink) an array, or otherwise reshape it in some way.
Currently supported growth options including changing the active
size of component devices and changing the number of active
devices in Linear and RAID levels 0/1/4/5/6, changing the RAID
level between 0, 1, 5, and 6, and between 0 and 10, changing the
chunk size and layout for RAID 0,4,5,6,10 as well as adding or
removing a write-intent bitmap and changing the array's
consistency policy.
Incremental Assembly
Add a single device to an appropriate array. If the addition of
the device makes the array runnable, the array will be started.
This provides a convenient interface to a hot-plug system. As
each device is detected, mdadm has a chance to include it in some
array as appropriate. Optionally, when the --fail flag is passed
in we will remove the device from any active array instead of
adding it.
If a CONTAINER is passed to mdadm in this mode, then any arrays
within that container will be assembled and started.
Manage This is for doing things to specific components of an array such
as adding new spares and removing faulty devices.
Misc This is an 'everything else' mode that supports operations on
active arrays, operations on component devices such as erasing old
superblocks, and information-gathering operations.
Auto-detect
This mode does not act on a specific device or array, but rather
it requests the Linux Kernel to activate any auto-detected arrays.
Options for selecting a mode are:
-A, --assemble
Assemble a pre-existing array.
-B, --build
Build a legacy array without superblocks.
-C, --create
Create a new array.
-F, --follow, --monitor
Select Monitor mode.
-G, --grow
Change the size or shape of an active array.
-I, --incremental
Add/remove a single device to/from an appropriate array, and
possibly start the array.
--auto-detect
Request that the kernel starts any auto-detected arrays. This can
only work if md is compiled into the kernel — not if it is a
module. Arrays can be auto-detected by the kernel if all the
components are in primary MS-DOS partitions with partition type
FD, and all use v0.90 metadata. In-kernel autodetect is not
recommended for new installations. Using mdadm to detect and
assemble arrays — possibly in an initrd — is substantially more
flexible and should be preferred.
If a device is given before any options, or if the first option is one of
--add, --re-add, --add-spare, --fail, --remove, or --replace, then the
MANAGE mode is assumed. Anything other than these will cause the Misc
mode to be assumed.
Options that are not mode-specific are:
-h, --help
Display a general help message or, after one of the above options,
a mode-specific help message.
--help-options
Display more detailed help about command-line parsing and some
commonly used options.
-V, --version
Print version information for mdadm.
-v, --verbose
Be more verbose about what is happening. This can be used twice
to be extra-verbose. The extra verbosity currently only affects
--detail --scan and --examine --scan.
-q, --quiet
Avoid printing purely informative messages. With this, mdadm will
be silent unless there is something really important to report.
-f, --force
Be more forceful about certain operations. See the various modes
for the exact meaning of this option in different contexts.
-c, --config=
Specify the config file or directory. If not specified, the
default config file and default conf.d directory will be used.
See mdadm.conf(5) for more details.
If the config file given is partitions then nothing will be read,
but mdadm will act as though the config file contained exactly
DEVICE partitions containers
and will read /proc/partitions to find a list of devices to scan,
and /proc/mdstat to find a list of containers to examine. If the
word none is given for the config file, then mdadm will act as
though the config file were empty.
If the name given is of a directory, then mdadm will collect all
the files contained in the directory with a name ending in .conf,
sort them lexically, and process all of those files as config
files.
-s, --scan
Scan config file or /proc/mdstat for missing information. In
general, this option gives mdadm permission to get any missing
information (like component devices, array devices, array
identities, and alert destination) from the configuration file
(see previous option); one exception is MISC mode when using
--detail or --stop, in which case --scan says to get a list of
array devices from /proc/mdstat.
-e, --metadata=
Declare the style of RAID metadata (superblock) to be used. The
default is 1.2 for --create, and to guess for other operations.
The default can be overridden by setting the metadata value for
the CREATE keyword in mdadm.conf.
Options are:
0, 0.90
Use the original 0.90 format superblock. This format
limits arrays to 28 component devices and limits component
devices of levels 1 and greater to 2 terabytes. It is also
possible for there to be confusion about whether the
superblock applies to a whole device or just the last
partition, if that partition starts on a 64K boundary.
1, 1.0, 1.1, 1.2 default
Use the new version-1 format superblock. This has fewer
restrictions. It can easily be moved between hosts with
different endian-ness, and a recovery operation can be
checkpointed and restarted. 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). "1" is equivalent to "1.2" (the
commonly preferred 1.x format). "default" is equivalent to
"1.2".
ddf Use the "Industry Standard" DDF (Disk Data Format) format
defined by SNIA. DDF is deprecated and there is no active
development around it. When creating a DDF array a
CONTAINER will be created, and normal arrays can be created
in that container.
imsm Use the Intel(R) Matrix Storage Manager metadata format.
This creates a CONTAINER which is managed in a similar
manner to DDF, and is supported by an option-rom on some
platforms:
https://www.intel.com/content/www/us/en/support/products/122484
--homehost=
This will override any HOMEHOST setting in the config file and
provides the identity of the host which should be considered the
home for any arrays.
When creating an array, the homehost will be recorded in the
metadata. For version-1 superblocks, it will be prefixed to the
array name. For version-0.90 superblocks, part of the SHA1 hash
of the hostname will be stored in the latter half of the UUID.
When reporting information about an array, any array which is
tagged for the given homehost will be reported as such.
When using Auto-Assemble, only arrays tagged for the given
homehost will be allowed to use 'local' names (i.e. not ending in
'_' followed by a digit string). See below under Auto-Assembly.
The special name "any" can be used as a wild card. If an array is
created with --homehost=any then the name "any" will be stored in
the array and it can be assembled in the same way on any host. If
an array is assembled with this option, then the homehost recorded
on the array will be ignored.
--prefer=
When mdadm needs to print the name for a device it normally finds
the name in /dev which refers to the device and is the shortest.
When a path component is given with --prefer mdadm will prefer a
longer name if it contains that component. For example
--prefer=by-uuid will prefer a name in a subdirectory of /dev
called by-uuid.
This functionality is currently only provided by --detail and
--monitor.
--home-cluster=
specifies the cluster name for the md device. The md device can be
assembled only on the cluster which matches the name specified. If
this option is not provided, mdadm tries to detect the cluster
name automatically.
For create, build, or grow:
-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
component-devices (including "missing" devices) that are listed on
the command line for --create. Setting a value of 1 is probably a
mistake and so requires that --force be specified first. A value
of 1 will then be allowed for linear, multipath, RAID0 and RAID1.
It is never allowed for RAID4, RAID5 or RAID6.
This number can only be changed using --grow for RAID1, RAID4,
RAID5 and RAID6 arrays.
-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.
-z, --size=
Amount (in Kilobytes) of space to use from each drive in RAID
levels 1/4/5/6/10 and for RAID 0 on external metadata. 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 (as it normally is not) the smallest drive (or
partition) sets the size, though if there is a variance among the
drives of greater than 1%, a warning is issued.
A suffix of 'K', 'M', 'G' or 'T' can be given to indicate
Kilobytes, Megabytes, Gigabytes or Terabytes respectively.
Sometimes a replacement drive can be a little smaller than the
original drives though this should be minimised by IDEMA
standards. Such a replacement drive will be rejected by md. To
guard against this it can be useful to set the initial size
slightly smaller than the smaller device with the aim that it will
still be larger than any replacement.
This option can be used with --create for determining the initial
size of an array. For external metadata, it can be used on a
volume, but not on a container itself. Setting the initial size
of RAID 0 array is only valid for external metadata.
This value can be set with --grow for RAID level 1/4/5/6/10 though
DDF arrays may not be able to support this. RAID 0 array size
cannot be changed. If the array was created with a size smaller
than the currently active drives, the extra space can be accessed
using --grow. The size can be given as max which means to choose
the largest size that fits on all current drives.
Before reducing the size of the array (with --grow --size=) you
should make sure that space isn't needed. If the device holds a
filesystem, you would need to resize the filesystem to use less
space.
After reducing the array size you should check that the data
stored in the device is still available. If the device holds a
filesystem, then an 'fsck' of the filesystem is a minimum
requirement. If there are problems the array can be made bigger
again with no loss with another --grow --size= command.
-Z, --array-size=
This is only meaningful with --grow and its effect is not
persistent: when the array is stopped and restarted the default
array size will be restored.
Setting the array-size causes the array to appear smaller to
programs that access the data. This is particularly needed before
reshaping an array so that it will be smaller. As the reshape is
not reversible, but setting the size with --array-size is, it is
required that the array size is reduced as appropriate before the
number of devices in the array is reduced.
Before reducing the size of the array you should make sure that
space isn't needed. If the device holds a filesystem, you would
need to resize the filesystem to use less space.
After reducing the array size you should check that the data
stored in the device is still available. If the device holds a
filesystem, then an 'fsck' of the filesystem is a minimum
requirement. If there are problems the array can be made bigger
again with no loss with another --grow --array-size= command.
A suffix of 'K', 'M', 'G' or 'T' can be given to indicate
Kilobytes, Megabytes, Gigabytes or Terabytes respectively. A
value of max restores the apparent size of the array to be
whatever the real amount of available space is.
Clustered arrays do not support this parameter yet.
-c, --chunk=
Specify chunk size in kilobytes. The default when creating an
array is 512KB. To ensure compatibility with earlier versions,
the default when building an array with no persistent metadata is
64KB. This is only meaningful for RAID0, RAID4, RAID5, RAID6, and
RAID10.
RAID4, RAID5, RAID6, and RAID10 require the chunk size to be a
power of 2, with minimal chunk size being 4KB.
A suffix of 'K', 'M', 'G' or 'T' can be given to indicate
Kilobytes, Megabytes, Gigabytes or Terabytes respectively.
--rounding=
Specify the rounding factor for a Linear array. The size of each
component will be rounded down to a multiple of this size. This
is a synonym for --chunk but highlights the different meaning for
Linear as compared to other RAID levels. The default is 0K (i.e.
no rounding).
-l, --level=
Set RAID level. When used with --create, options are: linear,
raid0, 0, stripe, raid1, 1, mirror, raid4, 4, raid5, 5, raid6, 6,
raid10, 10, multipath, mp, faulty, container. Obviously some of
these are synonymous.
When a CONTAINER metadata type is requested, only the container
level is permitted, and it does not need to be explicitly given.
When used with --build, only linear, stripe, raid0, 0, raid1,
multipath, mp, and faulty are valid.
Can be used with --grow to change the RAID level in some cases.
See LEVEL CHANGES below.
-p, --layout=
This option configures the fine details of data layout for RAID5,
RAID6, and RAID10 arrays, and controls the failure modes for
faulty. It can also be used for working around a kernel bug with
RAID0, but generally doesn't need to be used explicitly.
The layout of the RAID5 parity block can be one of
left-asymmetric, left-symmetric, right-asymmetric,
right-symmetric, la, ra, ls, rs. The default is left-symmetric.
It is also possible to cause RAID5 to use a RAID4-like layout by
choosing parity-first, or parity-last.
Finally for RAID5 there are DDF-compatible layouts,
ddf-zero-restart, ddf-N-restart, and ddf-N-continue.
These same layouts are available for RAID6. There are also 4
layouts that will provide an intermediate stage for converting
between RAID5 and RAID6. These provide a layout which is
identical to the corresponding RAID5 layout on the first N-1
devices, and has the 'Q' syndrome (the second 'parity' block used
by RAID6) on the last device. These layouts are:
left-symmetric-6, right-symmetric-6, left-asymmetric-6,
right-asymmetric-6, and parity-first-6.
When setting the failure mode for level faulty, the options are:
write-transient, wt, read-transient, rt, write-persistent, wp,
read-persistent, rp, write-all, read-fixable, rf, clear, flush,
none.
Each failure mode can be followed by a number, which is used as a
period between fault generation. Without a number, the fault is
generated once on the first relevant request. With a number, the
fault will be generated after that many requests, and will
continue to be generated every time the period elapses.
Multiple failure modes can be current simultaneously by using the
--grow option to set subsequent failure modes.
"clear" or "none" will remove any pending or periodic failure
modes, and "flush" will clear any persistent faults.
The layout options for RAID10 are one of 'n', 'o' or 'f' followed
by a small number signifying the number of copies of each
datablock. The default is 'n2'. The supported options are:
'n' signals 'near' copies. Multiple copies of one data block are
at similar offsets in different devices.
'o' signals 'offset' copies. Rather than the chunks being
duplicated within a stripe, whole stripes are duplicated but are
rotated by one device so duplicate blocks are on different
devices. Thus subsequent copies of a block are in the next drive,
and are one chunk further down.
'f' signals 'far' copies (multiple copies have very different
offsets). See md(4) for more detail about 'near', 'offset', and
'far'.
As for the number of copies of each data block, 2 is normal, 3 can
be useful. This number can be at most equal to the number of
devices in the array. It does not need to divide evenly into that
number (e.g. it is perfectly legal to have an 'n2' layout for an
array with an odd number of devices).
A bug introduced in Linux 3.14 means that RAID0 arrays with
devices of differing sizes started using a different layout. This
could lead to data corruption. Since Linux 5.4 (and various
stable releases that received backports), the kernel will not
accept such an array unless a layout is explicitly set. It can be
set to 'original' or 'alternate'. When creating a new array,
mdadm will select 'original' by default, so the layout does not
normally need to be set. An array created for either 'original'
or 'alternate' will not be recognized by an (unpatched) kernel
prior to 5.4. To create a RAID0 array with devices of differing
sizes that can be used on an older kernel, you can set the layout
to 'dangerous'. This will use whichever layout the running kernel
supports, so the data on the array may become corrupt when
changing kernel from pre-3.14 to a later kernel.
When an array is converted between RAID5 and RAID6 an intermediate
RAID6 layout is used in which the second parity block (Q) is
always on the last device. To convert a RAID5 to RAID6 and leave
it in this new layout (which does not require re-striping) use
--layout=preserve. This will try to avoid any restriping.
The converse of this is --layout=normalise which will change a
non-standard RAID6 layout into a more standard arrangement.
--parity=
same as --layout (thus explaining the p of -p).
-b, --bitmap=
Specify how to store a write-intent bitmap. Following values are
supported:
internal - the bitmap is stored with the metadata on the array and
so is replicated on all devices.
clustered - the array is created for a clustered environment. One
bitmap is created for each node as defined by the --nodes
parameter and are stored internally.
none - create array with no bitmap or remove any present bitmap
(grow mode).
Setting bitmap for file is deprecated and should not be used. The
file should not exist unless --force is also given. The same file
should be provided when assembling the array. The file name must
contain at least one slash ('/'). Bitmap files are only known to
work on ext2 and ext3. Storing bitmap files on other filesystems
may result in serious problems.
When creating an array on devices which are 100G or larger, mdadm
automatically adds an internal bitmap as it will usually be
beneficial. This can be suppressed with --bitmap=none or by
selecting a different consistency policy with
--consistency-policy.
--bitmap-chunk=
Set the chunk size of the bitmap. Each bit corresponds to that
many Kilobytes of storage. When using a file-based bitmap, the
default is to use the smallest size that is at least 4 and
requires no more than 2ˆ21 chunks. When using an internal bitmap,
the chunk size defaults to 64Meg, or larger if necessary to fit
the bitmap into the available space.
A suffix of 'K', 'M', 'G' or 'T' can be given to indicate
Kilobytes, Megabytes, Gigabytes or Terabytes respectively.
-W, --write-mostly
subsequent devices listed in a --build, --create, or --add command
will be flagged as 'write-mostly'. This is valid for RAID1 only
and means that the 'md' driver will avoid reading from these
devices if at all possible. This can be useful if mirroring over
a slow link.
--write-behind=
Specify that write-behind mode should be enabled (valid for RAID1
only). If an argument is specified, it will set the maximum
number of outstanding writes allowed. The default value is 256.
A write-intent bitmap is required in order to use write-behind
mode, and write-behind is only attempted on drives marked as
write-mostly.
--failfast
subsequent devices listed in a --create or --add command will be
flagged as 'failfast'. This is valid for RAID1 and RAID10 only.
IO requests to these devices will be encouraged to fail quickly
rather than cause long delays due to error handling. Also no
attempt is made to repair a read error on these devices.
If an array becomes degraded so that the 'failfast' device is the
only usable device, the 'failfast' flag will then be ignored and
extended delays will be preferred to complete failure.
The 'failfast' flag is appropriate for storage arrays which have a
low probability of true failure, but which may sometimes cause
unacceptable delays due to internal maintenance functions.
--assume-clean
Tell mdadm that the array pre-existed and is known to be clean.
It can be useful when trying to recover from a major failure as
you can be sure that no data will be affected unless you actually
write to the array. It can also be used when creating a RAID1 or
RAID10 if you want to avoid the initial resync, however this
practice — while normally safe — is not recommended. Use this
only if you really know what you are doing.
When the devices that will be part of a new array were filled with
zeros before creation the operator knows the array is actually
clean. If that is the case, such as after running badblocks, this
argument can be used to tell mdadm the facts the operator knows.
When an array is resized to a larger size with --grow --size= the
new space is normally resynced in that same way that the whole
array is resynced at creation. --assume-clean can be used with
that command to avoid the automatic resync.
--write-zeroes
When creating an array, send write zeroes requests to all the
block devices. This should zero the data area on all disks such
that the initial sync is not necessary and, if successful, will
behave as if --assume-clean was specified.
This is intended for use with devices that have hardware offload
for zeroing, but despite this zeroing can still take several
minutes for large disks. Thus a message is printed before and
after zeroing and each disk is zeroed in parallel with the others.
This is only meaningful with --create.
--backup-file=
This is needed when --grow is used to increase the number of raid
devices in a RAID5 or RAID6 if there are no spare devices
available, or to shrink, change RAID level or layout. See the
GROW MODE section below on RAID-DEVICES CHANGES. The file must be
stored on a separate device, not on the RAID array being reshaped.
--data-offset=
Arrays with 1.x metadata can leave a gap between the start of the
device and the start of array data. This gap can be used for
various metadata. The start of data is known as the data-offset.
Normally an appropriate data offset is computed automatically.
However it can be useful to set it explicitly such as when re-
creating an array which was originally created using a different
version of mdadm which computed a different offset.
Setting the offset explicitly over-rides the default. The value
given is in Kilobytes unless a suffix of 'K', 'M', 'G' or 'T' is
used to explicitly indicate Kilobytes, Megabytes, Gigabytes or
Terabytes respectively.
--data-offset can also be used with --grow for some RAID levels
(initially on RAID10). This allows the data-offset to be changed
as part of the reshape process. When the data offset is changed,
no backup file is required as the difference in offsets is used to
provide the same functionality.
When the new offset is earlier than the old offset, the number of
devices in the array cannot shrink. When it is after the old
offset, the number of devices in the array cannot increase.
When creating an array, --data-offset can be specified as
variable. In the case each member device is expected to have an
offset appended to the name, separated by a colon. This makes it
possible to recreate exactly an array which has varying data
offsets (as can happen when different versions of mdadm are used
to add different devices).
--continue
This option is complementary to the --freeze-reshape option for
assembly. It is needed when --grow operation is interrupted and it
is not restarted automatically due to --freeze-reshape usage
during array assembly. This option is used together with -G , (
--grow ) command and device for a pending reshape to be continued.
All parameters required for reshape continuation will be read from
array metadata. If initial --grow command had required
--backup-file= option to be set, continuation option will require
to have exactly the same backup file given as well.
Any other parameter passed together with --continue option will be
ignored.
-N, --name=
Set a name for the array. It must be POSIX PORTABLE NAME
compatible and cannot be longer than 32 chars. This is effective
when creating an array with a v1 metadata, or an external array.
If name is needed but not specified, it is taken from the basename
of the device that is being created. See DEVICE NAMES
-R, --run
Insist that mdadm run the array, even if some of the components
appear to be active in another array or filesystem. Normally
mdadm will ask for confirmation before including such components
in an array. This option causes that question to be suppressed.
-f, --force
Insist that mdadm accept the geometry and layout specified without
question. Normally mdadm will not allow the 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 --force, mdadm will not try to be so clever.
-o, --readonly
Start the array read only rather than read-write as normal. No
writes will be allowed to the array, and no resync, recovery, or
reshape will be started. It works with Create, Assemble, Manage
and Misc mode.
-a, --add
This option can be used in Grow mode in two cases.
If the target array is a Linear array, then --add can be used to
add one or more devices to the array. They are simply catenated
on to the end of the array. Once added, the devices cannot be
removed.
If the --raid-disks option is being used to increase the number of
devices in an array, then --add can be used to add some extra
devices to be included in the array. In most cases this is not
needed as the extra devices can be added as spares first, and then
the number of raid disks can be changed. However, for RAID0 it is
not possible to add spares. So to increase the number of devices
in a RAID0, it is necessary to set the new number of devices, and
to add the new devices, in the same command.
--nodes
Only works when the array is created for a clustered environment.
It specifies the maximum number of nodes in the cluster that will
use this device simultaneously. If not specified, this defaults to
4.
--write-journal
Specify journal device for the RAID-4/5/6 array. The journal
device should be an SSD with a reasonable lifetime.
-k, --consistency-policy=
Specify how the array maintains consistency in the case of an
unexpected shutdown. Only relevant for RAID levels with
redundancy. Currently supported options are:
resync Full resync is performed and all redundancy is regenerated
when the array is started after an unclean shutdown.
bitmap Resync assisted by a write-intent bitmap. Implicitly
selected when using --bitmap.
journal
For RAID levels 4/5/6, the journal device is used to log
transactions and replay after an unclean shutdown.
Implicitly selected when using --write-journal.
ppl For RAID5 only, Partial Parity Log is used to close the
write hole and eliminate resync. PPL is stored in the
metadata region of RAID member drives, no additional
journal drive is needed.
Can be used with --grow to change the consistency policy of an
active array in some cases. See CONSISTENCY POLICY CHANGES below.
For assemble:
-u, --uuid=
uuid of array to assemble. Devices which don't have this uuid are
excluded
-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 superblocks will contain the minor number 1,
even if the array is later assembled as /dev/md2.
Giving the literal word "dev" for --super-minor will cause mdadm
to use the minor number of the md device that is being assembled.
e.g. when assembling /dev/md0, --super-minor=dev will look for
super blocks with a minor number of 0.
--super-minor is only relevant for v0.90 metadata, and should not
normally be used. Using --uuid is much safer.
-N, --name=
Specify the name of the array to assemble. It must be POSIX
PORTABLE NAME compatible and cannot be longer than 32 chars. This
must be the name that was specified when creating the array. It
must either match the name stored in the superblock exactly, or it
must match with the current homehost prefixed to the start of the
given name.
-f, --force
Assemble the array even if the metadata on some devices appears to
be out-of-date. If mdadm cannot find enough working devices to
start the array, but can find some devices that are recorded as
having failed, then it will mark those devices as working so that
the array can be started. This works only for native. For external
metadata it allows to start dirty degraded RAID 4, 5, 6. An array
which requires --force to be started may contain data corruption.
Use it carefully.
-R, --run
Attempt to start the array even if fewer drives were given than
were present last time the array was active. Normally if not all
the expected drives are found and --scan is not used, then the
array will be assembled but not started. With --run an attempt
will be made to start it anyway.
--no-degraded
This is the reverse of --run in that it inhibits the startup of
array unless all expected drives are present. This is only needed
with --scan, and can be used if the physical connections to
devices are not as reliable as you would like.
-b, --bitmap=
Specify the bitmap file that was given when the array was created.
If an array has an internal bitmap, there is no need to specify
this when assembling the array.
--backup-file=
If --backup-file was used while reshaping an array (e.g. changing
number of devices or chunk size) and the system crashed during the
critical section, then the same --backup-file must be presented to
--assemble to allow possibly corrupted data to be restored, and
the reshape to be completed.
--invalid-backup
If the file needed for the above option is not available for any
reason an empty file can be given together with this option to
indicate that the backup file is invalid. In this case the data
that was being rearranged at the time of the crash could be
irrecoverably lost, but the rest of the array may still be
recoverable. This option should only be used as a last resort if
there is no way to recover the backup file.
-U, --update=
Update the superblock on each device while assembling the array.
The argument given to this flag can be one of summaries, uuid,
name, nodes, homehost, home-cluster, resync, byteorder,
devicesize, no-bitmap, bbl, no-bbl, ppl, no-ppl, layout-original,
layout-alternate, layout-unspecified, metadata, or super-minor.
The super-minor option will update the preferred minor field on
each superblock to match the minor number of the array being
assembled. This can be useful if --examine reports a different
"Preferred Minor" to --detail. In some cases this update will be
performed automatically by the kernel driver. In particular, the
update happens automatically at the first write to an array with
redundancy (RAID level 1 or greater).
The uuid option will change the uuid of the array. If a UUID is
given with the --uuid option that UUID will be used as a new UUID
and will NOT be used to help identify the devices in the array.
If no --uuid is given, a random UUID is chosen.
The name option will change the name of the array as stored in the
superblock. This is only supported for version-1 superblocks.
The nodes option will change the nodes of the array as stored in
the bitmap superblock. This option only works for a clustered
environment.
The homehost option will change the homehost as recorded in the
superblock. For version-0 superblocks, this is the same as
updating the UUID. For version-1 superblocks, this involves
updating the name.
The home-cluster option will change the cluster name as recorded
in the superblock and bitmap. This option only works for a
clustered environment.
The resync option will cause the array to be marked dirty meaning
that any redundancy in the array (e.g. parity for RAID5, copies
for RAID1) may be incorrect. This will cause the RAID system to
perform a "resync" pass to make sure that all redundant
information is correct.
The byteorder option allows arrays to be moved between machines
with different byte-order, such as from a big-endian machine like
a Sparc or some MIPS machines, to a little-endian x86_64 machine.
When assembling such an array for the first time after a move,
giving --update=byteorder will cause mdadm to expect superblocks
to have their byteorder reversed, and will correct that order
before assembling the array. This is only valid with original
(Version 0.90) superblocks.
The summaries option will correct the summaries in the superblock.
That is the counts of total, working, active, failed, and spare
devices.
The devicesize option will rarely be of use. It applies to
version 1.1 and 1.2 metadata only (where the metadata is at the
start of the device) and is only useful when the component device
has changed size (typically become larger). The version 1
metadata records the amount of the device that can be used to
store data, so if a device in a version 1.1 or 1.2 array becomes
larger, the metadata will still be visible, but the extra space
will not. In this case it might be useful to assemble the array
with --update=devicesize. This will cause mdadm to determine the
maximum usable amount of space on each device and update the
relevant field in the metadata.
The metadata option only works on v0.90 metadata arrays and will
convert them to v1.0 metadata. The array must not be dirty (i.e.
it must not need a sync) and it must not have a write-intent
bitmap.
The old metadata will remain on the devices, but will appear older
than the new metadata and so will usually be ignored. The old
metadata (or indeed the new metadata) can be removed by giving the
appropriate --metadata= option to --zero-superblock.
The no-bitmap option can be used when an array has an internal
bitmap which is corrupt in some way so that assembling the array
normally fails. It will cause any internal bitmap to be ignored.
The bbl option will reserve space in each device for a bad block
list. This will be 4K in size and positioned near the end of any
free space between the superblock and the data.
The no-bbl option will cause any reservation of space for a bad
block list to be removed. If the bad block list contains entries,
this will fail, as removing the list could cause data corruption.
The ppl option will enable PPL for a RAID5 array and reserve space
for PPL on each device. There must be enough free space between
the data and superblock and a write-intent bitmap or journal must
not be used.
The no-ppl option will disable PPL in the superblock.
The layout-original and layout-alternate options are for RAID0
arrays with non-uniform devices size that were in use before Linux
5.4. If the array was being used with Linux 3.13 or earlier, then
to assemble the array on a new kernel, --update=layout-original
must be given. If the array was created and used with a kernel
from Linux 3.14 to Linux 5.3, then --update=layout-alternate must
be given. This only needs to be given once. Subsequent assembly
of the array will happen normally. For more information, see
md(4).
The layout-unspecified option reverts the effect of layout-orignal
or layout-alternate and allows the array to be again used on a
kernel prior to Linux 5.3. This option should be used with great
caution.
--freeze-reshape
This option is intended to be used in start-up scripts during the
initrd boot phase. When the array under reshape is assembled
during the initrd phase, this option stops the reshape after the
reshape-critical section has been restored. This happens before
the file system pivot operation and avoids loss of filesystem
context. Losing file system context would cause reshape to be
broken.
Reshape can be continued later using the --continue option for the
grow command.
For Manage mode:
-t, --test
Unless a more serious error occurred, mdadm will exit with a
status of 2 if no changes were made to the array and 0 if at least
one change was made. This can be useful when an indirect
specifier such as missing, detached or faulty is used in
requesting an operation on the array. --test will report failure
if these specifiers didn't find any match.
-a, --add
hot-add listed devices. If a device appears to have recently been
part of the array (possibly it failed or was removed) the device
is re-added as described in the next point. If that fails or the
device was never part of the array, the device is added as a hot-
spare. If the array is degraded, it will immediately start to
rebuild data onto that spare.
Note that this and the following options are only meaningful on
array with redundancy. They don't apply to RAID0 or Linear.
--re-add
re-add a device that was previously removed from an array. If the
metadata on the device reports that it is a member of the array,
and the slot that it used is still vacant, then the device will be
added back to the array in the same position. This will normally
cause the data for that device to be recovered. However, based on
the event count on the device, the recovery may only require
sections that are flagged by a write-intent bitmap to be recovered
or may not require any recovery at all.
When used on an array that has no metadata (i.e. it was built with
--build) it will be assumed that bitmap-based recovery is enough
to make the device fully consistent with the array.
--re-add can also be accompanied by --update=devicesize,
--update=bbl, or --update=no-bbl. See descriptions of these
options when used in Assemble mode for an explanation of their
use.
If the device name given is missing then mdadm will try to find
any device that looks like it should be part of the array but
isn't and will try to re-add all such devices.
If the device name given is faulty then mdadm will find all
devices in the array that are marked faulty, remove them and
attempt to immediately re-add them. This can be useful if you are
certain that the reason for failure has been resolved.
--add-spare
Add a device as a spare. This is similar to --add except that it
does not attempt --re-add first. The device will be added as a
spare even if it looks like it could be a recent member of the
array.
-r, --remove
remove listed devices. They must not be active. i.e. they should
be failed or spare devices.
As well as the name of a device file (e.g. /dev/sda1) the words
failed, detached and names like set-A can be given to --remove.
The first causes all failed devices to be removed. The second
causes any device which is no longer connected to the system (i.e
an 'open' returns ENXIO) to be removed. The third will remove a
set as described below under --fail.
-f, --fail
Mark listed devices as faulty. As well as the name of a device
file, the word detached or a set name like set-A can be given.
The former will cause any device that has been detached from the
system to be marked as failed. It can then be removed.
For RAID10 arrays where the number of copies evenly divides the
number of devices, the devices can be conceptually divided into
sets where each set contains a single complete copy of the data on
the array. Sometimes a RAID10 array will be configured so that
these sets are on separate controllers. In this case, all the
devices in one set can be failed by giving a name like set-A or
set-B to --fail. The appropriate set names are reported by
--detail.
--set-faulty
same as --fail.
--replace
Mark listed devices as requiring replacement. As soon as a spare
is available, it will be rebuilt and will replace the marked
device. This is similar to marking a device as faulty, but the
device remains in service during the recovery process to increase
resilience against multiple failures. When the replacement
process finishes, the replaced device will be marked as faulty.
--with This can follow a list of --replace devices. The devices listed
after --with will preferentially be used to replace the devices
listed after --replace. These devices must already be spare
devices in the array.
--write-mostly
Subsequent devices that are added or re-added will have the
'write-mostly' flag set. This is only valid for RAID1 and means
that the 'md' driver will avoid reading from these devices if
possible.
--readwrite
Subsequent devices that are added or re-added will have the
'write-mostly' flag cleared.
--cluster-confirm
Confirm the existence of the device. This is issued in response to
an --add request by a node in a cluster. When a node adds a device
it sends a message to all nodes in the cluster to look for a
device with a UUID. This translates to a udev notification with
the UUID of the device to be added and the slot number. The
receiving node must acknowledge this message with
--cluster-confirm. Valid arguments are <slot>:<devicename> in case
the device is found or <slot>:missing in case the device is not
found.
--add-journal
Add a journal to an existing array, or recreate journal for a
RAID-4/5/6 array that lost a journal device. To avoid interrupting
ongoing write operations, --add-journal only works for array in
Read-Only state.
--failfast
Subsequent devices that are added or re-added will have the
'failfast' flag set. This is only valid for RAID1 and RAID10 and
means that the 'md' driver will avoid long timeouts on error
handling where possible.
--nofailfast
Subsequent devices that are re-added will be re-added without the
'failfast' flag set.
mdadm 创建 RAID 数组：
sudo mdadm --create /dev/md/MyRAID --level raid_level --raid-devices number_of_disks /dev/sdXN
mdadm 停止 RAID 数组：
sudo mdadm --stop /dev/md0
mdadm 将磁盘标记为故障：
sudo mdadm --fail /dev/md0 /dev/sdXN
mdadm 移除磁盘：
sudo mdadm --remove /dev/md0 /dev/sdXN
mdadm 将磁盘添加到阵列：
sudo mdadm --assemble /dev/md0 /dev/sdXN
mdadm 显示 RAID 信息：
sudo mdadm --detail /dev/md0
mdadm 通过删除 RAID 元数据重置磁盘：
sudo mdadm --zero-superblock /dev/sdXN