Provided by: xfsprogs_2.9.4-2_i386
mkfs.xfs - construct an XFS filesystem
mkfs.xfs [ -b block_size ] [ -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 ] device
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:
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-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=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
b - multiply by filesystem block size (default = 4K, see -b
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).
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.
These options specify the location, size, and other parameters
of the data section of the filesystem. The valid
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
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.
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
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
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.
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.
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.
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
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
When a filesystem is created on a logical volume
device, mkfs.xfs will automatically query the
logical volume for appropriate sunit and swidth
This is used to specify whether unwritten extents
are flagged as such, or not. The 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, filesystem write performance
will be negatively affected for preallocated file
extents, since extra filesystem transactions are
required to convert extent flags for the range of
the file written. This suboption should be disabled
if the filesystem needs to be used on operating
system versions which do not support the flagging
-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
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 | 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 mininum (and default) value is
256 bytes. 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 sufficently
large, mkfs.xfs will warn if this will create inode
numbers > 32 significant bits.
This 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 essentially all of the filesystem can become
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).
This is used to specify the version of extended
attribute inline allocation policy to be used. By
default, this is zero. Once extended attributes are
used for the first time, the version will be set to
either one or two. The current version (two) uses a
more efficient algorithm for managing the available
inline inode space than version one does, however,
for backward compatibility reasons (and in the
absence of the attr=2 mkfs option, or the attr2
mount option), version one will be selected by
default when attributes are first used on a
These options specify the location, size, and other parameters
of the log section of the filesystem. The valid
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.
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
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
This specifies the version of the log. The value is
either 1 or 2. Specifying version=2 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.
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.
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
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 serialisation 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 0 (off) so you must specify
lazy-count=1 if you want to make use of this
These options specify the version and size parameters for the
naming (directory) area of the filesystem. The valid
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 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.
The naming (directory) version value can be either 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
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.
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
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
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
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.
These options specify the location, size, and other parameters
of the real-time section of the filesystem. The valid
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.
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.
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.
This option specifies the fundamental sector size of the
filesystem. The sector_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.
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
-N Causes the file system parameters to be printed out without
really creating the file system.
xfs(5), mkfs(8), mount(8), xfs_info(8), xfs_admin(8).
With a prototype file, it is not possible to specify hard links.