||FreeBSD System Manager's Manual
mkfs.xfs - construct an XFS filesystem
[ -b block_size
] [ -m
] [ -d data_section_options
] [ -i inode_options
] [ -l
] [ -n naming_options
] [ -p
] [ -q
] [ -r realtime_section_options
[ -s sector_size
] [ -L label
] [ -N
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
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,
mkfs.xfs -l logdev=/dev/sdb1,size=10000b
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
internal -l size=10000b
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
m - multiply by one megabyte (1,048,576
g - multiply by one gigabyte (1,073,741,824
t - multiply by one terabyte
p - multiply by one petabyte (1,024
e - multiply by one exabyte (1,048,576
- -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:
- 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 noticable in normal operation.
- By default, mkfs.xfs will enable metadata CRCs.
- 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
- -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:
- 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
- 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 real-time section.
- 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.
- 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
- 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
- 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 sunit suboption.
- 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.
- This option disables automatic geometry detection and creates the
filesystem without stripe geometry alignment even if the underlying
storage device provides this information.
- 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: 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 |
- 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 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
- 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
- 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
- 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).
- 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 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
- 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
- -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:
- 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 exclusive.
- 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.
- 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.
- 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
serialization point in the filesystem. The value can be either 0 or
- 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
- -n naming_options
- These options specify the version and size parameters for the naming
(directory) area of the filesystem. The valid naming_options
- 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
- 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
- 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
- Note: Version 1 directories are not supported.
- 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 signifiying that filetype
information will be stored in the directory structure. The default value
When CRCs are enabled via -m crc=1, the ftype functionality is always
enabled. This feature can not be turned off for such filesystem
- -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
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
- 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
- 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
- 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.
- Quiet option. Normally mkfs.xfs prints the parameters of the
filesystem to be constructed; 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
- 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
- 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
- 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
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.
- -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
- Causes the file system parameters to be printed out without really
creating the file system.
- Do not attempt to discard blocks at mkfs time.
- Prints the version number and exits.
With a prototype file, it is not possible to specify hard links.
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