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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 subopt=value ] [ -d subopt[=value] ]
            [ -i subopt=value ] [ -l subopt[=value] ] [ -f ]
            [ -n subopt[=value] ] [ -p protofile ] [ -q ]
            [ -r subopt[=value] ] [ -s subopt[=value] ]
            [ -N ] [ -L label ] device

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 mkfs is given the -t xfs option.

       In its simplest (and most commonly used form), the size of the filesys-
       tem 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  subopt=value  elements in the argument list above can be
       given as multiple comma-separated subopt=value 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=10000b and -l internal -l size=10000b are equivalent.

       In  the  descriptions below, sizes are given in sectors, bytes, blocks,
       kilobytes, megabytes, or gigabytes.  Sizes are treated  as  hexadecimal
       if  prefixed by 0x or 0X, octal if prefixed by 0, or decimal otherwise.
       If suffixed with s then the size is converted by multiplying it by  the
       filesystems  sector  size  (defaults  to 512, see -s option below).  If
       suffixed with b then the size is converted by  multiplying  it  by  the
       filesystems  block size (defaults to 4K, see -b option below).  If suf-
       fixed with k then the size is converted by multiplying it by 1024.   If
       suffixed with m then the size is converted by multiplying it by 1048576
       (1024 * 1024).  If suffixed with g then the size is converted by multi-
       plying it by 1073741824 (1024 * 1024 * 1024).

       -b     Block size options.

              This option specifies the fundamental block size of the filesys-
              tem.  The valid suboptions are: log=value and  size=value;  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 KB), the minimum is 512, and the
              maximum is 65536 (64 KB).  XFS on Linux currently only  supports
              pagesize or smaller blocks.

       -d     Data section options.

              These  options  specify the location, size, and other parameters
              of the data section of the  filesystem.   The  valid  suboptions
              are:   agcount=value,  agsize=value,  file[=value],  name=value,
              size=value, sunit=value, swidth=value, su=value,  sw=value,  and
              unwritten[=value].

              The  agcount  suboption is used to specify the number of alloca-
              tion groups.  The data section of the filesystem is divided into
              allocation groups to improve the performance of XFS.  More allo-
              cation groups imply that more parallelism can be  achieved  when
              allocating blocks and inodes.  The minimum allocation group size
              is 16 MB; the maximum size is just under 4 GB.  The data section
              of  the  filesystem  is  divided  into agcount allocation groups
              (default value 8, unless the filesystem is smaller than  128  MB
              or  larger  than  8 GB).  Setting agcount to a very large number
              should be avoided, since this causes an unreasonable  amount  of
              CPU time to be used when the filesystem is close to full.

              The  agsize  suboption  is an alternative to using agcount.  The
              argument provided to agsize is the desired size of  the  alloca-
              tion  group  expressed  in  bytes (usually using the m or g suf-
              fixes).  This value must be a multiple of the  filesystem  block
              size,  and  must be at least 16MB, and no more than 4GB, and may
              be automatically adjusted to  properly  align  with  the  stripe
              geometry.   The  agcount  suboption and the agsize suboption are
              mutually exclusive.

              The name suboption can be used to specify the name of  the  spe-
              cial file containing the filesystem.  In this case, the log sec-
              tion must be specified as internal (with  a  size,  see  the  -l
              option below) and there can be no real-time section.

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

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

              The sunit suboption is used to specify the  stripe  unit  for  a
              RAID  device or a logical volume.  The suboption 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 512KB.  Also inode allocations and the internal log will be
              stripe unit aligned.

              The  su suboption is an alternative to using sunit.  The su sub-
              option is used to specify the stripe unit for a RAID device or a
              striped logical volume.  The suboption 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.

              The  swidth  suboption is used to specify the stripe width for a
              RAID device or a striped logical volume.   The  suboption  value
              has  to be specified in 512-byte block units.  Use the sw subop-
              tion 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.  The stripe  width  will  be
              the preferred iosize returned in the stat(2) system call.

              The sw suboption is an alternative to using swidth.  The sw sub-
              option is used to specify the stripe width for a RAID device  or
              striped  logical  volume.  The suboption 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 appro-
              priate sunit and swidth values.

              The unwritten suboption is used  to  specify  whether  unwritten
              extents  are  flagged  as  such, or not.  The suboption value is
              either 0 or 1, with 1 signifying that unwritten extent  flagging
              should  occur.   If  the  suboption is omitted, unwritten extent
              flagging is enabled.  If unwritten extents are flagged, filesys-
              tem  write  performance will be negatively affected for preallo-
              cated file extents,  since  extra  filesystem  transactions  are
              required to convert extent flags for the range of the file writ-
              ten.  This suboption should be disabled if the filesystem  needs
              to be used on operating system versions which do not support the
              flagging capability.

       -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; 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  suboptions for specifying inode size are: log=value,
              perblock=value, and size=value; only one can be  supplied.   The
              inode  size  is  specified  either as a base two logarithm value
              with log=, in bytes with size=, or as the number  fitting  in  a
              filesystem  block  with  perblock=.   The  mininum (and default)
              value is 256 bytes.  The maximum value is 2048 (2 KB) 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 and most applications
              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 sufficently large, mkfs.xfs will warn if this will
              create inode numbers > 32 significant bits.

              The  option  maxpct=value  specifies  the  maximum percentage of
              space in the filesystem that can be allocated  to  inodes.   The
              default  value is 25%.  Setting the value to 0 means that essen-
              tially all of the filesystem can become inode blocks.

              The option align[=value] is used to specify that  inode  alloca-
              tion  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 filesys-
              tem 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).

       -l     Log section options.

              These options specify the location, size, and  other  parameters
              of the log section of the filesystem.  The valid suboptions are:
              internal[=value],  logdev=device,   size=value,   version=[1|2],
              sunit=value, and su=value.

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

              The  logdev  suboption  is  used to specify that the log section
              should reside on a device separate from the data  section.   The
              suboption  value  is the name of a block device.  The internal=1
              and logdev options are mutually exclusive.

              The size suboption is used to specify the size of the  log  sec-
              tion.

              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 size 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.

              Using the version suboption to specify a version 2  log  enables
              the  sunit  suboption,  and  allows the logbsize to be increased
              beyond 32K.  Version 2 logs are automatically selected if a  log
              stripe unit is specified.  See sunit and su suboptions, below.

              The  sunit  suboption specifies the alignment to be used for log
              writes.  The suboption 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  bound-
              ary, and rounded up to this boundary.  This gives major improve-
              ments 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 su suboption is specified.

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

       -n     Naming options.

              These  options  specify  the version and size parameters for the
              naming (directory) area of the filesystem.  The valid suboptions
              are:  log=value,  size=value,  and  version=value.   The  naming
              (directory) version is 1 or 2, 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
              block  size  is  specified  either as a base two logarithm value
              with log=, or in bytes with size=.  The default size  value  for
              version  2 directories is 4096 bytes (4 KB), unless the filesys-
              tem 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.

       -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  follow-
              ing 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 compati-
              bility:  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 command to  terminate  the  branch  of  the
              filesystem  it is currently on and then continue from the direc-
              tory 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 pro-
              totype 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 regu-
              lar file, a block special file, a character special file, direc-
              tory  files,  named  pipes (first-in, first out files), and sym-
              bolic 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  speci-
              fied,  the  second  character is -.  The remaining characters of
              the mode string are a three digit octal number. This octal  num-
              ber defines the owner, group, and other read, write, and execute
              permissions for the file, respectively.  Form  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  num-
              bers  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     Real-time section options.

              These options specify the location, size, and  other  parameters
              of  the  real-time  section of the filesystem.  The valid subop-
              tions are: rtdev=device, extsize=value, and size=value.

              The rtdev suboption 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.

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

              The  size suboption 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.

       -s     Sector size options.

              This  option  specifies  the  fundamental  sector  size  of  the
              filesystem.  The valid suboptions are: log=value and size=value;
              only one can be supplied.  The sector size is  specified  either
              as a base two logarithm value with log=, or in bytes with size=.
              The default value is 512 bytes.  The minimum  value  for  sector
              size is 512; the maximum is 32768 (32 KB).  The sector size must
              be a power of 2 size and cannot be made larger than the filesys-
              tem 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.

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)