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mkfs.xfs(8)                          System Manager's Manual                          mkfs.xfs(8)

NAME
       mkfs.xfs - construct an XFS filesystem

SYNOPSIS
       mkfs.xfs [ -b block_size ] [ -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 ] [ -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 10000  block  log
       located on the first partition on the second SCSI disk, use:

              mkfs.xfs -l logdev=/dev/sdb1,size=10000b /dev/sda1

       Each of the option elements in the argument list above can be given as multiple comma-sep‐
       arated suboptions if multiple suboptions apply to the  same  option.   Equivalently,  each
       main option can be given multiple times with different suboptions.  For example, -l inter‐
       nal,size=10000b and -l internal -l size=10000b 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).

OPTIONS
       -b block_size_options
              This  option  specifies  the  fundamental  block size of the filesystem.  The valid
              block_size_options are: log=value or size=value and only one can be supplied.   The
              block size is specified either as a base two logarithm value with log=, or in bytes
              with size=.  The default value is 4096 bytes (4 KiB), the minimum is 512,  and  the
              maximum  is  65536  (64  KiB).   XFS  on  Linux currently only supports pagesize or
              smaller blocks.

       -m global_metadata_options
              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:

                   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 depen‐
                          dent 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 cre‐
                          ated 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.

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

       -d data_section_options
              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 sec‐
                          tion 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  alloca‐
                          tion  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.

                   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 cur‐
                          rent  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 suf‐
                          fixes). 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 vol‐
                          ume. The value is expressed as a multiplier of the stripe unit, usually
                          the same as the number of stripe members in the logical volume configu‐
                          ration, 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.

       -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
              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:  direc‐
              tory  data,  for  small directories; attribute data, for small attribute sets; sym‐
              bolic 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 | log=value | perblock=value
                          The inode size is specified either as a value in bytes  with  size=,  a
                          base  two  logarithm  value  with  log=,  or as the number fitting in a
                          filesystem block with perblock=.  The minimum (and  default)  value  is
                          256  bytes.   The maximum value is 2048 (2 KiB) subject to the restric‐
                          tion that the inode size cannot exceed one half of the filesystem block
                          size.

                          XFS  uses  64-bit inode numbers internally; however, the number of sig‐
                          nificant bits in an inode number is affected  by  filesystem  geometry.
                          In  practice,  filesystem  size and inode size are the predominant fac‐
                          tors.  The Linux kernel (on 32 bit hardware platforms) and most  appli‐
                          cations  cannot currently handle inode numbers greater than 32 signifi‐
                          cant 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  suffi‐
                          ciently  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 signifi‐
                          cant 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  allo‐
                          cation  policy  to be used.  By default, this is 2, which uses an effi‐
                          cient 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 omit‐
                          ted, 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
              These  options  specify the location, size, and other parameters of the log section
              of the filesystem. The valid log_section_options are:

                   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 speci‐
                          fied, 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 mul‐
                          tiplication by the filesystem block size, as described above. The over‐
                          riding minimum value for size is 512 blocks.  With some combinations of
                          filesystem  block size, inode size, and directory block size, the mini‐
                          mum 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 spec‐
                          ify 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  automati‐
                          cally 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
              These  options  specify  the version and size parameters for the naming (directory)
              area of the filesystem. The valid naming_options are:

                   size=value | log=value
                          The block size is specified either as a value in bytes with  size=,  or
                          as  a  base  two  logarithm  value with log=.  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',  default‐
                          ing  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 cre‐
                          ated with.

                          Note: Version 1 directories are not supported.

                   ftype=value
                          This feature allows the inode type to be stored in the directory struc‐
                          ture  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 signifiying that  filetype  informa‐
                          tion will be stored in the directory structure. The default value is 0.

                          When  CRCs  are enabled via -m crc=1, the ftype functionality is always
                          enabled. This feature can not be turned off for such filesystem config‐
                          urations.

       -p protofile
              If the optional -p protofile argument is given, mkfs.xfs uses protofile as a proto‐
              type file and takes its directions from that file.  The blocks  and  inodes  speci‐
              fiers  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 immate‐
              rial 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 com‐
              mand 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  charac‐
              ters  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 recur‐
              sive 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 con‐
              structed; the -q flag suppresses this.

       -r realtime_section_options
              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 subop‐
                          tion is only needed if the real-time section of the  filesystem  should
                          occupy less space than the size of the partition or logical volume con‐
                          taining the section.

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

       -s sector_size
              This  option  specifies  the  fundamental  sector size of the filesystem.  The sec‐
              tor_size is specified either as a value in bytes with size=value or as a  base  two
              logarithm  value with log=value.  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.

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)

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