path: root/mdctl.8

.\" -*- nroff -*-
.TH mdctl 8
.SH NAME
mdctl \- a single program that can be used to control Linux md devices
.SH SYNOPSIS

.BI mdctl 
[mode] <raiddevice> [options]

.SH DESCRIPTION 
RAID devices are virtual devices created from two or more
real block devices. This allows multiple disks to be combined into a single
filesystem, possibly with integrated redundancy to survive drive failure.. Linux RAID devices
are implemented through the md device driver.

If you're using the 
.B /proc 
filesystem,
.B /proc/mdstat
gives you informations about md devices status.

Currently, Linux supports linear md devices, RAID0 (striping), RAID1
(mirrroring), RAID4 and RAID5. For information on the various levels of
RAID, check out:

  http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/

for new releases of the RAID driver check out:

  ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches

.B mdctl 
is a single program that can be used to control Linux md devices. It
is intended to provide all the functionality (and more) of the mdtools
and raidtools but with a very different interface.

mdctl can perform all functions without a configuration file. There is the
option of using a configuration file, but not in the same way that raidtools
uses one. raidtools uses a configuration file to describe how to create a
RAID array, and also uses this file partially to start a previously created
RAID array. Further, raidtools requires the configuration file for such
things as stopping a raid array which needs to know nothing about the array.

The configuration file that can be used by mdctl lists two different things:

.IP "\fB\-\fP"
a list of md devices and information about how to identify each.  The
identity can consist of a UUID, and minor-number as recorded on the
superblock, or a list of devices.

.IP "\fB\-\fP"
a list of devices that should be scanned for md sub-devices.

.SH MODES
mdctl has 4 major modes of operation:
.IP "\fBCreate\fP"
This mode is used to create a new array with a superblock. It can progress
in several step create-add-add-run or it can all happen with one command.

.IP "\fBAssemble\fP"
This mode is used to assemble the parts of a previously created
array into an active array. Components can be explicitly given
or can be searched for. 
.B mdctl
(optionally) checks that the components
do form a bonafide array, and can, on request, fiddle superblock
version numbers so as to assemble a faulty array.

.IP "\fBBuild\fP"
This is for building legacy arrays without superblocks.

.IP "\fBManage\fP"
This is for odd bits an pieces like hotadd, hotremove, setfaulty, stop,
readonly,readwrite If an array is only partially setup by the
Create/Assemble/Build command, subsequent Manage commands can finish the
job.

.SH OPTIONS

Available options are:

.IP "\fB\-C\fP, \fB\-\-create\fP"
Create a new array

.IP "\fB-A\fP, \fB\-\-assemble\fP"
Assemble an existing array

.IP "\fB\-B\fP, \fB\-\-build\fP"
Build a legacy array without superblock

.IP "\fB\-D\fP, \fB\-\-detail\fP"
Print detail of a given md array

.IP "\fB\-E\fP, \fB\-\-examine\fP"
Print content of md superblock on device

.IP "\fB\-h\fP, \fB\-\-help\fP"
This help message or, after above option, mode specific help message

.IP "\fB\-V\fP, \fB\-\-version\fP"
Print version information for mdctl

.IP "\fB\-v\fP, \fB\-\-verbose\fP"
Be more verbose about what is happening

.SH For create or build:

.IP "\fB\-c\fP, \fB\-\-chunk=\fP"
chunk size of kibibytes

.IP "\fB\-\-rounding=\fP"
rounding factor for linear array (==chunk size)

.IP "\fB\-l\fP, \fB\-\-level=\fP"
raid level: 0,1,4,5,linear. 0 or linear for build

.IP "\fB\-p\fP, \fB\-\-parity=\fP"
raid5 parity algorithm: {left,right}-{,a}symmetric

.IP "\fB\-\-layout=\fP"
same as --parity

.IP "\fB\-n\fP, \fB\-\-raid-disks=\fP"
number of active devices in array

.IP "\fB\-x\fP, \fB\-\-spare-disks=\fP"
number of spares (eXtras) to allow space for

.IP "\fB\-z\fP, \fB\-\-size=\fP"
Size (in K) of each drive in RAID1/4/5 - optional

.SH For assemble:

.IP "\fB\-u\fP, \fB\-\-uuid=\fP"
uuid of array to assemble. Devices which don't have this uuid are excluded

.IP "\fB\-c\fP, \fB\-\-config=\fP"
config file

.IP "\fB\-s\fP, \fB\-\-scan\fP"
scan config file for missing information

.IP "\fB\-f\fP, \fB\-\-force\fP"
Assemble the array even if some superblocks appear out-of-date

.SH General management

.IP "\fB\-a\fP, \fB\-\-add\fP"
add, or hotadd subsequent devices

.IP "\fB\-r\fP, \fB\-\-remove\fP"
remove subsequent devices

.IP "\fB\-f\fP, \fB\-\-fail\fP"
mark subsequent devices a faulty

.IP "\fB\-\-set-faulty\fP"
same as --fail

.IP "\fB\-R\fP, \fB\-\-run\fP"
start a partially built array

.IP "\fB\-S\fP, \fB\-\-stop\fP"
deactivate array, releasing all resources

.IP "\fB\-o\fP, \fB\-\-readonly\fP"
mark array as readonly

.IP "\fB\-w\fP, \fB\-\-readwrite\fP"
mark array as readwrite

.SH CREATE MODE

Usage:

.B mdctl
--create device --chunk=X --level=Y --raid-disks=Z devices

This usage will initialise a new md array and possibly associate some
devices with it. If enough devices are given to complete the array, the
array will be activated. Otherwise it will be left inactive to be completed
and activated by subsequent management commands.

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
device size exceeds 1%.

If any discrepancy is found, the array will not automatically be run, though
the presence of a 
.B --run
can override this caution.

If the 
.B --size
option is given, it is not necessary to list any subdevices in this command.
They can be added later, before a
.B --run. 
If no 
.B --size
is given, the apparent size of the smallest drive given is used.

The General management options that are valid with --create are:
.IP "\fB\-\-run\fP"
insist of running the array even if not all devices are present or some look
odd.

.IP "\fB\-\-readonly\fP"
start the array readonly - not supported yet.

.SH ASSEMBLY MODE

Usage: 

.B mdctl
--assemble device options...

.B mdctl
--assemble --scan options...

This usage assembles one or more raid arrays from pre-existing components.
For each array, mdctl needs to know the md device, the uuid, and a number of
sub devices. These can be found in a number of ways.

The md device is either given before 
.B --scan
or is found from the config file. In the latter case, multiple md devices
can be started with a single mdctl command.

The uuid can be given with the 
.B --uuid
option, or 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 or in a
subsequent
.B --add
command.

Devices can be given on the 
.B --assemble
command line, on subsequent
.B 'mdctl --add'
command lines, or from the config file. Only devices which have an md
superblock which contains the right uuid will be considered for any device.

The config file is only used if explicitly named with 
.B --config
or requested with 
.B --scan. 
In the later case,
.B /etc/md.conf
is used.

If 
.B --scan
is not given, then the config file will only be used to find uuids for md
arrays.

The format of the config file is:
   not yet documented

.SH BUILD MDOE

Usage:

.B mdctl 
--build device -chunk=X --level=Y --raid-disks=Z devices

This usage is similar to 
.B --create. 
The difference is that it creates a legacy array without a superblock. With
these arrays there is no different between initially creating the array and
subsequently assembling the array, except that hopefully there is useful
data there in the second case.

The level may only be 0 or linear. All devices must be listed and the array
will be started once complete.

.SH BUGS
no known bugs.

.SH TODO


.SH SEE ALSO
.IR raidtab (5),
.IR raid0run (8),
.IR raidstop (8),
.IR mkraid (8)