Provided by: xfsprogs_5.10.0-2ubuntu3_amd64 bug

NAME

       mkfs.xfs - construct an XFS filesystem

SYNOPSIS

       mkfs.xfs   [   -b   block_size_options   ]   [   -m   global_metadata_options   ]   [   -d
       data_section_options ] [ -f ] [ -i  inode_options  ]  [  -l  log_section_options  ]  [  -n
       naming_options  ]  [  -p  protofile  ]  [  -q  ]  [  -r  realtime_section_options  ]  [ -s
       sector_size_options ] [ -L label ] [ -N ] [ -K ] device
       mkfs.xfs -V

DESCRIPTION

       mkfs.xfs constructs an XFS filesystem by writing on a special file using the values  found
       in  the  arguments of the command line.  It is invoked automatically by mkfs(8) when it is
       given the -t xfs option.

       In its simplest (and most commonly used form), the size of the  filesystem  is  determined
       from  the  disk  driver.   As an example, to make a filesystem with an internal log on the
       first partition on the first SCSI disk, use:

              mkfs.xfs /dev/sda1

       The metadata log can be placed on another device to reduce the number of disk  seeks.   To
       create a filesystem on the first partition on the first SCSI disk with a 10MiB log located
       on the first partition on the second SCSI disk, use:

              mkfs.xfs -l logdev=/dev/sdb1,size=10m /dev/sda1

       Each of the option elements in the argument list above can be  given  as  multiple  comma-
       separated  suboptions if multiple suboptions apply to the same option.  Equivalently, each
       main option can be given multiple  times  with  different  suboptions.   For  example,  -l
       internal,size=10m and -l internal -l size=10m are equivalent.

       In  the  descriptions  below,  sizes  are  given  in  sectors,  bytes,  blocks, kilobytes,
       megabytes, gigabytes, etc.  Sizes are treated as hexadecimal if  prefixed  by  0x  or  0X,
       octal if prefixed by 0, or decimal otherwise.  The following lists possible multiplication
       suffixes:
              s - multiply by sector size (default = 512, see -s option below).
              b - multiply by filesystem block size (default = 4K, see -b option below).
              k - multiply by one kilobyte (1,024 bytes).
              m - multiply by one megabyte (1,048,576 bytes).
              g - multiply by one gigabyte (1,073,741,824 bytes).
              t - multiply by one terabyte (1,099,511,627,776 bytes).
              p - multiply by one petabyte (1,024 terabytes).
              e - multiply by one exabyte (1,048,576 terabytes).

       When specifying parameters in units of sectors or filesystem blocks, the -s option or  the
       -b  option  may  be  used  to specify the size of the sector or block.  If the size of the
       block or sector is not specified, the default sizes (block: 4KiB, sector:  512B)  will  be
       used.

       Many feature options allow an optional argument of 0 or 1, to explicitly disable or enable
       the functionality.

OPTIONS

       Options may be specified either on the command line or in a configuration file.   Not  all
       command  line  options  can  be  specified  in  configuration files; only the command line
       options followed by a [section] label can be used in a configuration file.

       Options that can be  used  in  configuration  files  are  grouped  into  related  sections
       containing  multiple  options.   The  command line options and configuration files use the
       same option sections and grouping.  Configuration file section names  are  listed  in  the
       command line option sections below.  Option names and values are the same for both command
       line and configuration file specification.

       Options specified are the combined set of command line parameters and  configuration  file
       parameters.   Duplicated options will result in a respecification error, regardless of the
       location they were specified at.

       -c configuration_file_option
              This option specifies the files that mkfs configuration will be obtained from.  The
              valid configuration_file_option is:

                   options=name
                          The  configuration  options  will be sourced from the file specified by
                          the name option string.  This option can be use either an  absolute  or
                          relative path to the configuration file to be read.

       -b block_size_options
       Section Name: [block]
              This  option  specifies  the  fundamental  block size of the filesystem.  The valid
              block_size_option is:

                   size=value
                          The filesystem block size is specified  with  a  value  in  bytes.  The
                          default  value  is  4096  bytes  (4  KiB),  the minimum is 512, and the
                          maximum is 65536 (64 KiB).

                          Although mkfs.xfs will accept any of these values and  create  a  valid
                          filesystem,  XFS  on  Linux can only mount filesystems with pagesize or
                          smaller blocks.

       -m global_metadata_options
       Section Name: [metadata]
              These options specify metadata format options  that  either  apply  to  the  entire
              filesystem  or  aren't  easily characterised by a specific functionality group. The
              valid global_metadata_options are:

                   bigtime=value
                          This option enables filesystems that can handle inode  timestamps  from
                          December  1901  to  July 2486, and quota timer expirations from January
                          1970 to July 2486.  The value is either 0 to disable the feature, or  1
                          to enable large timestamps.

                          If  this  feature  is  not  enabled,  the  filesystem  can  only handle
                          timestamps from December 1901 to January 2038, and  quota  timers  from
                          January 1970 to February 2106.

                          By  default,  mkfs.xfs  will not enable this feature.  If the option -m
                          crc=0 is used, the large timestamp feature  is  not  supported  and  is
                          disabled.

                   crc=value
                          This  is  used  to  create  a filesystem which maintains and checks CRC
                          information in all metadata objects on disk. The value is either  0  to
                          disable the feature, or 1 to enable the use of CRCs.

                          CRCs enable enhanced error detection due to hardware issues, whilst the
                          format changes also improves crash recovery algorithms and the  ability
                          of  various tools to validate and repair metadata corruptions when they
                          are found.  The CRC algorithm  used  is  CRC32c,  so  the  overhead  is
                          dependent  on  CPU architecture as some CPUs have hardware acceleration
                          of this algorithm.  Typically the overhead of calculating and  checking
                          the CRCs is not noticeable in normal operation.

                          By default, mkfs.xfs will enable metadata CRCs.

                   finobt=value
                          This  option  enables  the  use of a separate free inode btree index in
                          each allocation group. The value is either 0 to disable the feature, or
                          1 to create a free inode btree in each allocation group.

                          The  free  inode btree mirrors the existing allocated inode btree index
                          which indexes both used and free inodes. The free inode btree does  not
                          index  used  inodes,  allowing faster, more consistent inode allocation
                          performance as filesystems age.

                          By default, mkfs.xfs will create  free  inode  btrees  for  filesystems
                          created  with  the  (default)  -m  crc=1 option set. When the option -m
                          crc=0 is used, the free inode btree feature is  not  supported  and  is
                          disabled.

                   inobtcount=value
                          This  option  causes the filesystem to record the number of blocks used
                          by the inode btree and the free inode  btree.   This  can  be  used  to
                          reduce mount times when the free inode btree is enabled.

                          By default, mkfs.xfs will not enable this option.  This feature is only
                          available for filesystems created with the (default) -m finobt=1 option
                          set.   When  the  option  -m  finobt=0 is used, the inode btree counter
                          feature is not supported and is disabled.

                   uuid=value
                          Use the given value as  the  filesystem  UUID  for  the  newly  created
                          filesystem.  The default is to generate a random UUID.

                   rmapbt=value
                          This  option  enables  the creation of a reverse-mapping btree index in
                          each allocation group.  The value is either 0 to disable  the  feature,
                          or 1 to create the btree.

                          The  reverse  mapping  btree maps filesystem blocks to the owner of the
                          filesystem block.  Most of the mappings will be to an inode number  and
                          an  offset,  though there will also be mappings to filesystem metadata.
                          This secondary metadata can be used to validate the primary metadata or
                          to pinpoint exactly which data has been lost when a disk error occurs.

                          By  default,  mkfs.xfs  will  not  create reverse mapping btrees.  This
                          feature is only available for filesystems created with the (default) -m
                          crc=1 option set. When the option -m crc=0 is used, the reverse mapping
                          btree feature is not supported and is disabled.

                   reflink=value
                          This option enables the use of a separate reference count  btree  index
                          in each allocation group. The value is either 0 to disable the feature,
                          or 1 to create a reference count btree in each allocation group.

                          The reference count btree  enables  the  sharing  of  physical  extents
                          between  the  data forks of different files, which is commonly known as
                          "reflink".  Unlike traditional Unix filesystems which assume that every
                          inode and logical block pair map to a unique physical block, a reflink-
                          capable XFS filesystem removes the uniqueness requirement, allowing  up
                          to  four  billion  arbitrary  inode/logical  block  pairs  to  map to a
                          physical block.  If a program tries to write to  a  multiply-referenced
                          block  in a file, the write will be redirected to a new block, and that
                          file's logical-to-physical mapping will be changed  to  the  new  block
                          ("copy  on  write").   This  feature  enables  the creation of per-file
                          snapshots and deduplication.  It is only available for the  data  forks
                          of regular files.

                          By  default,  mkfs.xfs will create reference count btrees and therefore
                          will enable the reflink feature.  This feature is  only  available  for
                          filesystems  created  with  the (default) -m crc=1 option set. When the
                          option -m crc=0 is used, the  reference  count  btree  feature  is  not
                          supported and reflink is disabled.

                          Note:  the  filesystem DAX mount option ( -o dax ) is incompatible with
                          reflink-enabled XFS filesystems.   To  use  filesystem  DAX  with  XFS,
                          specify  the  -m  reflink=0  option  to mkfs.xfs to disable the reflink
                          feature.

       -d data_section_options
       Section Name: [data]
              These options specify the location, size, and other parameters of the data  section
              of the filesystem. The valid data_section_options are:

                   agcount=value
                          This  is  used  to  specify  the  number of allocation groups. The data
                          section of the filesystem is divided into allocation groups to  improve
                          the  performance  of  XFS.  More  allocation  groups  imply  that  more
                          parallelism can be achieved when  allocating  blocks  and  inodes.  The
                          minimum allocation group size is 16 MiB; the maximum size is just under
                          1 TiB.  The data section  of  the  filesystem  is  divided  into  value
                          allocation  groups  (default value is scaled automatically based on the
                          underlying device size).

                   agsize=value
                          This is an alternative to using the agcount suboption. The value is the
                          desired  size of the allocation group expressed in bytes (usually using
                          the m or g suffixes).  This value must be a multiple of the  filesystem
                          block  size, and must be at least 16MiB, and no more than 1TiB, and may
                          be automatically adjusted to properly align with the  stripe  geometry.
                          The agcount and agsize suboptions are mutually exclusive.

                   cowextsize=value
                          Set  the  copy-on-write  extent  size  hint  on  all  inodes created by
                          mkfs.xfs.  The value must be provided in units  of  filesystem  blocks.
                          If  the  value is zero, the default value (currently 32 blocks) will be
                          used.  Directories will pass on this  hint  to  newly  created  regular
                          files and directories.

                   name=value
                          This can be used to specify the name of the special file containing the
                          filesystem. In this case, the log section must be specified as internal
                          (with  a  size,  see the -l option below) and there can be no real-time
                          section.

                   file[=value]
                          This is used to specify that the file given by the name suboption is  a
                          regular  file.  The  value is either 0 or 1, with 1 signifying that the
                          file is regular. This suboption is  used  only  to  make  a  filesystem
                          image. If the value is omitted then 1 is assumed.

                   size=value
                          This is used to specify the size of the data section. This suboption is
                          required if -d file[=1] is given. Otherwise, it is only needed  if  the
                          filesystem should occupy less space than the size of the special file.

                   sunit=value
                          This  is used to specify the stripe unit for a RAID device or a logical
                          volume. The value has to be specified in 512-byte block units. Use  the
                          su  suboption  to specify the stripe unit size in bytes. This suboption
                          ensures that data allocations will be  stripe  unit  aligned  when  the
                          current  end of file is being extended and the file size is larger than
                          512KiB. Also inode allocations and the internal log will be stripe unit
                          aligned.

                   su=value
                          This  is  an  alternative  to using sunit.  The su suboption is used to
                          specify the stripe unit for a RAID device or a striped logical  volume.
                          The  value  has  to  be  specified  in bytes, (usually using the m or g
                          suffixes). This value must be a multiple of the filesystem block size.

                   swidth=value
                          This is used to specify the stripe width for a RAID device or a striped
                          logical  volume. The value has to be specified in 512-byte block units.
                          Use the sw suboption to specify the stripe width size in  bytes.   This
                          suboption is required if -d sunit has been specified and it has to be a
                          multiple of the -d sunit suboption.

                   sw=value
                          suboption is an alternative to using swidth.  The sw suboption is  used
                          to  specify  the  stripe  width  for  a  RAID device or striped logical
                          volume. The value is expressed as a  multiplier  of  the  stripe  unit,
                          usually  the same as the number of stripe members in the logical volume
                          configuration, or data disks in a RAID device.

                          When a filesystem is created on a logical volume device, mkfs.xfs  will
                          automatically query the logical volume for appropriate sunit and swidth
                          values.

                   noalign
                          This option disables  automatic  geometry  detection  and  creates  the
                          filesystem  without  stripe  geometry  alignment even if the underlying
                          storage device provides this information.

                   rtinherit=value
                          If value is set to 1, all inodes created by mkfs.xfs  will  be  created
                          with  the  realtime flag set.  The default is 0.  Directories will pass
                          on this flag to newly created regular files and directories.

                   projinherit=value
                          All inodes created by mkfs.xfs will be assigned the  project  quota  id
                          provided  in  value.   Directories will pass on the project id to newly
                          created regular files and directories.

                   extszinherit=value
                          All inodes created by mkfs.xfs will have this value  extent  size  hint
                          applied.   The  value  must  be provided in units of filesystem blocks.
                          Directories will pass on this hint to newly created regular  files  and
                          directories.

                   daxinherit=value
                          If  value  is  set to 1, all inodes created by mkfs.xfs will be created
                          with the DAX flag set.  The default is 0.   Directories  will  pass  on
                          this  flag to newly created regular files and directories.  By default,
                          mkfs.xfs will not enable DAX mode.

       -f     Force overwrite when an existing filesystem is detected on the device.  By default,
              mkfs.xfs  will not write to the device if it suspects that there is a filesystem or
              partition table on the device already.

       -i inode_options
       Section Name: [inode]
              This option specifies the inode size of the filesystem, and other inode  allocation
              parameters.   The  XFS  inode  contains a fixed-size part and a variable-size part.
              The variable-size part, whose  size  is  affected  by  this  option,  can  contain:
              directory  data,  for  small directories; attribute data, for small attribute sets;
              symbolic link data, for small symbolic links; the extent list  for  the  file,  for
              files  with  a  small  number  of  extents;  and  the root of a tree describing the
              location of extents for the file, for files with a large number of extents.

              The valid inode_options are:

                   size=value | perblock=value
                          The inode size is specified either as a value in bytes with size= or as
                          the  number  fitting in a filesystem block with perblock=.  The minimum
                          (and default) value is 256  bytes  without  crc,  512  bytes  with  crc
                          enabled.   The maximum value is 2048 (2 KiB) subject to the restriction
                          that the inode size cannot exceed one  half  of  the  filesystem  block
                          size.

                          XFS  uses  64-bit  inode  numbers  internally;  however,  the number of
                          significant bits in an inode number is affected by filesystem geometry.
                          In  practice,  filesystem  size  and  inode  size  are  the predominant
                          factors.  The Linux kernel (on 32  bit  hardware  platforms)  and  most
                          applications  cannot  currently  handle  inode  numbers greater than 32
                          significant bits, so if no inode size is given  on  the  command  line,
                          mkfs.xfs  will attempt to choose a size such that inode numbers will be
                          < 32 bits.  If an inode size  is  specified,  or  if  a  filesystem  is
                          sufficiently  large,  mkfs.xfs  will  warn  if  this  will create inode
                          numbers > 32 significant bits.

                   maxpct=value
                          This specifies the maximum percentage of space in the  filesystem  that
                          can  be  allocated  to inodes. The default value is 25% for filesystems
                          under 1TB, 5% for filesystems under 50TB and 1%  for  filesystems  over
                          50TB.

                          In the default inode allocation mode, inode blocks are chosen such that
                          inode numbers will not exceed 32 bits, which restricts the inode blocks
                          to  the  lower portion of the filesystem. The data block allocator will
                          avoid these low blocks to accommodate the specified maxpct, so  a  high
                          value  may  result  in  a  filesystem  with  nothing  but  inodes  in a
                          significant portion of the  lower  blocks  of  the  filesystem.   (This
                          restriction  is  not  present  when  the filesystem is mounted with the
                          inode64 option on 64-bit platforms).

                          Setting the value to 0 means that essentially all of the filesystem can
                          become inode blocks, subject to inode32 restrictions.

                          This value can be modified with xfs_growfs(8).

                   align[=value]
                          This is used to specify that inode allocation is or is not aligned. The
                          value is either 0 or 1, with 1 signifying  that  inodes  are  allocated
                          aligned.   If  the  value is omitted, 1 is assumed. The default is that
                          inodes are aligned.  Aligned inode access is  normally  more  efficient
                          than  unaligned  access;  alignment must be established at the time the
                          filesystem is created, since inodes are allocated at that  time.   This
                          option  can  be  used  to  turn off inode alignment when the filesystem
                          needs to be mountable by a version of IRIX that does not have the inode
                          alignment feature (any release of IRIX before 6.2, and IRIX 6.2 without
                          XFS patches).

                   attr=value
                          This is used to  specify  the  version  of  extended  attribute  inline
                          allocation  policy  to  be  used.  By default, this is 2, which uses an
                          efficient algorithm for  managing  the  available  inline  inode  space
                          between attribute and extent data.

                          The  previous  version  1,  which  has  fixed regions for attribute and
                          extent data, is kept for backwards  compatibility  with  kernels  older
                          than version 2.6.16.

                   projid32bit[=value]
                          This  is  used  to enable 32bit quota project identifiers. The value is
                          either 0 or 1, with 1 signifying that 32bit projid are to  be  enabled.
                          If  the  value  is  omitted,  1  is  assumed.  (This default changed in
                          release version 3.2.0.)

                   sparse[=value]
                          Enable sparse inode chunk allocation. The value is either 0 or 1,  with
                          1  signifying  that  sparse  allocation  is  enabled.   If the value is
                          omitted, 1 is assumed. Sparse inode allocation is disabled by  default.
                          This feature is only available for filesystems formatted with -m crc=1.

                          When enabled, sparse inode allocation allows the filesystem to allocate
                          smaller than the standard 64-inode chunk when free  space  is  severely
                          limited.  This  feature  is  useful for filesystems that might fragment
                          free space over time such that no free  extents  are  large  enough  to
                          accommodate  a  chunk of 64 inodes. Without this feature enabled, inode
                          allocations can fail with out of space errors under  severe  fragmented
                          free space conditions.

       -l log_section_options
       Section Name: [log]
              These  options  specify the location, size, and other parameters of the log section
              of the filesystem. The valid log_section_options are:

                   agnum=value
                          If the log is internal, allocate it in this AG.

                   internal[=value]
                          This is used to specify that the log section is a  piece  of  the  data
                          section instead of being another device or logical volume. The value is
                          either 0 or 1, with 1 signifying that the log is internal. If the value
                          is omitted, 1 is assumed.

                   logdev=device
                          This  is  used  to  specify  that  the log section should reside on the
                          device separate from  the  data  section.  The  internal=1  and  logdev
                          options are mutually exclusive.

                   size=value
                          This is used to specify the size of the log section.

                          If  the  log  is  contained  within  the  data  section  and size isn't
                          specified, mkfs.xfs will try to select a suitable log size depending on
                          the  size  of  the  filesystem.   The  actual  logsize  depends  on the
                          filesystem block size and the directory block size.

                          Otherwise, the size suboption is only needed if the log section of  the
                          filesystem  should occupy less space than the size of the special file.
                          The value is specified in bytes or blocks,  with  a  b  suffix  meaning
                          multiplication  by  the  filesystem block size, as described above. The
                          overriding  minimum  value  for  size  is  512   blocks.    With   some
                          combinations  of filesystem block size, inode size, and directory block
                          size, the minimum log size is larger than 512 blocks.

                   version=value
                          This specifies the version of the log. The current default is 2,  which
                          allows  for  larger  log  buffer  sizes,  as well as supporting stripe-
                          aligned log writes (see the sunit and su options, below).

                          The previous version 1, which is limited to 32k log  buffers  and  does
                          not  support stripe-aligned writes, is kept for backwards compatibility
                          with very old 2.4 kernels.

                   sunit=value
                          This specifies the alignment to be used for log writes. The  value  has
                          to  be  specified  in  512-byte  block  units.  Use the su suboption to
                          specify the log stripe unit size in bytes.  Log writes will be  aligned
                          on  this  boundary,  and rounded up to this boundary.  This gives major
                          improvements in performance on some  configurations  such  as  software
                          RAID5  when  the  sunit is specified as the filesystem block size.  The
                          equivalent byte value must be a multiple of the filesystem block  size.
                          Version 2 logs are automatically selected if the log sunit suboption is
                          specified.

                          The su suboption is an alternative to using sunit.

                   su=value
                          This is used to specify the log stripe. The value has to  be  specified
                          in  bytes,  (usually  using  the s or b suffixes). This value must be a
                          multiple  of  the  filesystem  block  size.    Version   2   logs   are
                          automatically selected if the log su suboption is specified.

                   lazy-count=value
                          This  changes  the method of logging various persistent counters in the
                          superblock.  Under metadata intensive  workloads,  these  counters  are
                          updated and logged frequently enough that the superblock updates become
                          a serialization point in the filesystem. The value can be either  0  or
                          1.

                          With  lazy-count=1,  the  superblock is not modified or logged on every
                          change of the persistent counters. Instead, enough information is  kept
                          in  other parts of the filesystem to be able to maintain the persistent
                          counter values without needed to keep them  in  the  superblock.   This
                          gives  significant  improvements in performance on some configurations.
                          The default value is 1 (on) so you must  specify  lazy-count=0  if  you
                          want to disable this feature for older kernels which don't support it.

       -n naming_options
       Section Name: [naming]
              These  options  specify  the version and size parameters for the naming (directory)
              area of the filesystem. The valid naming_options are:

                   size=value
                          The directory block size is specified with a value in bytes.  The block
                          size  must be a power of 2 and cannot be less than the filesystem block
                          size.  The default size value for version 2 directories is  4096  bytes
                          (4 KiB), unless the filesystem block size is larger than 4096, in which
                          case the default value is the filesystem block  size.   For  version  1
                          directories the block size is the same as the filesystem block size.

                   version=value
                          The  naming  (directory)  version  value  can  be  either  2  or  'ci',
                          defaulting to 2  if  unspecified.   With  version  2  directories,  the
                          directory  block  size  can  be any power of 2 size from the filesystem
                          block size up to 65536.

                          The version=ci option  enables  ASCII  only  case-insensitive  filename
                          lookup  and  version 2 directories. Filenames are case-preserving, that
                          is, the names are stored  in  directories  using  the  case  they  were
                          created with.

                          Note: Version 1 directories are not supported.

                   ftype=value
                          This  feature  allows  the  inode  type  to  be stored in the directory
                          structure so that the readdir(3) and getdents(2) do not need to look up
                          the inode to determine the inode type.

                          The value is either 0 or 1, with 1 signifying that filetype information
                          will be stored in the directory structure.  The default value is 1.

                          When CRCs are enabled (the default), the ftype functionality is  always
                          enabled, and cannot be turned off.

       -p protofile
              If  the  optional  -p  protofile  argument  is  given, mkfs.xfs uses protofile as a
              prototype file and takes its directions from that  file.   The  blocks  and  inodes
              specifiers  in  the  protofile  are  provided  for backwards compatibility, but are
              otherwise unused.  The syntax of the protofile is defined by  a  number  of  tokens
              separated  by  spaces  or  newlines. Note that the line numbers are not part of the
              syntax but are meant to help you in the following discussion of the file contents.

                   1       /stand/diskboot
                   2       4872 110
                   3       d--777 3 1
                   4       usr     d--777 3 1
                   5       sh      ---755 3 1 /bin/sh
                   6       ken     d--755 6 1
                   7               $
                   8       b0      b--644 3 1 0 0
                   9       c0      c--644 3 1 0 0
                   10      fifo    p--644 3 1
                   11      slink   l--644 3 1 /a/symbolic/link
                   12      :  This is a comment line
                   13      $
                   14      $

              Line 1 is a dummy string.  (It was formerly the bootfilename.)  It is  present  for
              backward compatibility; boot blocks are not used on SGI systems.

              Note  that some string of characters must be present as the first line of the proto
              file to cause it to be parsed correctly; the value of  this  string  is  immaterial
              since it is ignored.

              Line  2  contains  two  numeric values (formerly the numbers of blocks and inodes).
              These are also merely for backward compatibility: two numeric values must appear at
              this  point  for  the  proto  file  to  be  correctly  parsed, but their values are
              immaterial since they are ignored.

              The lines 3 through 11 specify the files and directories you  want  to  include  in
              this  filesystem.  Line  3  defines the root directory. Other directories and files
              that you want in the filesystem are indicated by lines 4  through  6  and  lines  8
              through 10. Line 11 contains symbolic link syntax.

              Notice  the  dollar  sign  ($)  syntax  on line 7. This syntax directs the mkfs.xfs
              command to terminate the branch of the filesystem  it  is  currently  on  and  then
              continue  from  the  directory specified by the next line, in this case line 8.  It
              must be the last character on a line.  The colon on line 12 introduces  a  comment;
              all  characters  up  until the following newline are ignored.  Note that this means
              you cannot have a file in a prototype file whose name contains a colon.  The  $  on
              lines 13 and 14 end the process, since no additional specifications follow.

              File specifications provide the following:

                * file mode
                * user ID
                * group ID
                * the file's beginning contents

              A  6-character  string  defines  the  mode  for a file. The first character of this
              string defines the file type. The character  range  for  this  first  character  is
              -bcdpl.   A  file  may be a regular file, a block special file, a character special
              file, directory files, named pipes (first-in, first out files), and symbolic links.
              The second character of the mode string is used to specify setuserID mode, in which
              case it is u.  If setuserID mode is not specified, the second character is -.   The
              third character of the mode string is used to specify the setgroupID mode, in which
              case it is g.  If setgroupID mode is not specified, the third character is -.   The
              remaining  characters of the mode string are a three digit octal number. This octal
              number defines the owner, group, and other read, write, and execute permissions for
              the file, respectively.  For more information on file permissions, see the chmod(1)
              command.

              Following the mode character string are two decimal number tokens that specify  the
              user and group IDs of the file's owner.

              In  a  regular  file, the next token specifies the pathname from which the contents
              and size of the file are copied.  In a block or character special  file,  the  next
              token  are  two  decimal  numbers  that specify the major and minor device numbers.
              When a file is a symbolic link, the next token specifies the contents of the link.

              When the file is a directory, the mkfs.xfs command creates the entries dot (.)  and
              dot-dot  (..)  and  then  reads  the  list  of  names  and file specifications in a
              recursive manner for all of the entries in the directory. A scan of  the  protofile
              is always terminated with the dollar ( $ ) token.

       -q     Quiet  option.  Normally  mkfs.xfs  prints  the  parameters of the filesystem to be
              constructed; the -q flag suppresses this.

       -r realtime_section_options
       Section Name: [realtime]
              These options specify the location, size, and other  parameters  of  the  real-time
              section of the filesystem. The valid realtime_section_options are:

                   rtdev=device
                          This  is  used to specify the device which should contain the real-time
                          section of the filesystem.  The suboption value is the name of a  block
                          device.

                   extsize=value
                          This is used to specify the size of the blocks in the real-time section
                          of the filesystem. This value must be  a  multiple  of  the  filesystem
                          block  size. The minimum allowed size is the filesystem block size or 4
                          KiB (whichever is larger); the default size is  the  stripe  width  for
                          striped  volumes or 64 KiB for non-striped volumes; the maximum allowed
                          size is 1 GiB. The real-time extent size should be carefully chosen  to
                          match the parameters of the physical media used.

                   size=value
                          This  is  used  to  specify  the  size  of the real-time section.  This
                          suboption is only needed if the real-time  section  of  the  filesystem
                          should  occupy  less  space  than  the size of the partition or logical
                          volume containing the section.

                   noalign
                          This option disables stripe size detection, enforcing a realtime device
                          with no stripe geometry.

       -s sector_size_options
       Section Name: [sector]
              This  option  specifies  the  fundamental sector size of the filesystem.  The valid
              sector_size_option is:

                   size=value
                          The sector size is specified  with  a  value  in  bytes.   The  default
                          sector_size is 512 bytes. The minimum value for sector size is 512; the
                          maximum is 32768 (32 KiB). The sector_size must be a power  of  2  size
                          and cannot be made larger than the filesystem block size.

       -L label
              Set the filesystem label.  XFS filesystem labels can be at most 12 characters long;
              if label is longer than 12 characters, mkfs.xfs will not proceed with creating  the
              filesystem.   Refer  to the mount(8) and xfs_admin(8) manual entries for additional
              information.

       -N     Causes the file system parameters to be printed out  without  really  creating  the
              file system.

       -K     Do not attempt to discard blocks at mkfs time.

       -V     Prints the version number and exits.

Configuration File Format

       The  configuration  file  uses a basic INI format to specify sections and options within a
       section.  Section and option names are case sensitive.  Section  names  must  not  contain
       whitespace.   Options  are  name-value  pairs,  ended by the first whitespace in the line.
       Option names cannot contain whitespace.  Full line comments can be  added  by  starting  a
       line with a # symbol.  If values contain whitespace, then it must be quoted.

       The  following  example  configuration  file  sets  the block size to 4096 bytes, turns on
       reverse mapping btrees and sets the inode size to 2048 bytes.

       # Example mkfs.xfs configuration file

       [block]
       size=4k

       [metadata]
       rmapbt=1

       [inode]
       size=2048

SEE ALSO

       xfs(5), mkfs(8), mount(8), xfs_info(8), xfs_admin(8).

BUGS

       With a prototype file, it is not possible to specify hard links.

                                                                                      mkfs.xfs(8)