Usage: mdadm --assemble md-device options-and-component-devices...
 
      Usage: mdadm --assemble --scan md-devices-and-options...
 
      Usage: mdadm --assemble --scan options...
 
      This  usage  assembles one or more raid arrays from pre-existing compo-
      nents.  For each array, mdadm needs to know the md device, the identity
      of  the array, and a number of component-devices. These can be found in
      a number of ways.
 
      In the first usage example (without the --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 configura-
      tion file are assembled.
 
      If precisely one device is listed, but --scan is not given, then  mdadm
      acts  as  though --scan was given and identify information is extracted
      from the configuration file.
 
      The identity can be given with the --uuid  option,  with  the  --super-
      minor  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 --assemble 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 --config or
      requested with (a  possibly  implicit)  --scan.   In  the  later  case,
      /etc/mdadm.conf is used.
 
      If  --scan 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  if
      --scan is not given and insufficient drives were listed to start a com-
      plete (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, 4, 5 or 6), give the --run flag.
 
      If an auto option is given, either on the command line (--auto)  or  in
      the  configuration file (e.g. auto=part), then mdadm will create the md
      device if necessary or will re-create it if it doesn't look  usable  as
      it is.
 
      This can be useful for handling partitioned devices (which don't have a
      stable device number - it can change after a  reboot)  and  when  using
      "udev"  to manage your /dev tree (udev cannot handle md devices because
      of the unusual device initialisation conventions).
 
      If the option to "auto" is "mdp" or "part"  or  (on  the  command  line
      only)  "p",  then  mdadm  will  create a partitionable array, using the
      first free one that is not inuse, and does not already have an entry in
      /dev (apart from numeric /dev/md* entries).
 
      If the option to "auto" is "yes" or "md" or (on the command line) noth-
      ing, then mdadm will create a traditional, non-partitionable md  array.
 
      It  is  expected  that  the "auto" functionality will be used to create
      device  entries  with  meaningful  names  such  as  "/dev/md/home"   or
      "/dev/md/root",  rather than names based on the numerical array number.
 
      When using this option to create  a  partitionable  array,  the  device
      files  for the first 4 partitions are also created. If a different num-
      ber is required it can be simply appended to  the  auto  option.   e.g.
      "auto=part8".   Partition names are created by appending a digit string
      to the device name, with an intervening "p" if  the  device  name  ends
      with a digit.
 
      The  --auto  option  is  also  available in Build and Create modes.  As
      those modes do not use a config file, the "auto="  config  option  does
      not apply to these modes.