man/man8/mkfs.xfs.8.in

.TH mkfs.xfs 8
.SH NAME
mkfs.xfs \- construct an XFS filesystem
.SH SYNOPSIS
.B mkfs.xfs
[
.B \-b
.I block_size_options
] [
.B \-c
.I config_file_options
] [
.B \-m
.I global_metadata_options
] [
.B \-d
.I data_section_options
] [
.B \-f
] [
.B \-i
.I inode_options
] [
.B \-l
.I log_section_options
] [
.B \-n
.I naming_options
] [
.B \-p
.I protofile_options
] [
.B \-q
] [
.B \-r
.I realtime_section_options
] [
.B \-s
.I sector_size_options
] [
.B \-L
.I label
] [
.B \-N
] [
.B \-K
]
.I device
.br
.B mkfs.xfs \-V
.SH DESCRIPTION
.B 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
.BR mkfs (8)
when it is given the
.B \-t xfs
option.
.PP
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:
.IP
.B mkfs.xfs /dev/sda1
.PP
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 100MiB log located on the first partition
on the second SCSI disk, use:
.RS
.HP
.B mkfs.xfs\ \-l\ logdev=/dev/sdb1,size=100m /dev/sda1
.RE
.PP
Each of the
.I 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,
.B \-l internal,size=100m
and
.B \-l internal \-l size=100m
are equivalent.
.PP
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:
.RS
.PD 0
.HP
.BR s "\ \-\ multiply by sector size (default = 512, see " \-s
option below).
.HP
.BR b "\ \-\ multiply by filesystem block size (default = 4K, see " \-b
option below).
.HP
.BR k "\ \-\ multiply by one kilobyte (1,024 bytes)."
.HP
.BR m "\ \-\ multiply by one megabyte (1,048,576 bytes)."
.HP
.BR g "\ \-\ multiply by one gigabyte (1,073,741,824 bytes)."
.HP
.BR t "\ \-\ multiply by one terabyte (1,099,511,627,776 bytes)."
.HP
.BR p "\ \-\ multiply by one petabyte (1,024 terabytes)."
.HP
.BR e "\ \-\ multiply by one exabyte (1,048,576 terabytes)."
.PD
.RE
.PP
When specifying parameters in units of sectors or filesystem blocks, the
.B \-s
option or the
.B \-b
option may be used to specify the size of the sector or block.
If the size of the block or sector is not specified, the default sizes
(block: 4KiB, sector: 512B) will be used.
.PP
Many feature options allow an optional argument of 0 or 1, to explicitly
disable or enable the functionality.

The correctness of the crc32c checksum implementation will be tested
before formatting the filesystem.
If the test fails, the format will abort.
.SH OPTIONS
Options may be specified either on the command line or in a configuration file.
Not all command line options can be specified in configuration files; only the
command line options followed by a
.B [section]
label can be used in a configuration file.
.PP
Options that can be used in configuration files are grouped into related
sections containing multiple options.
The command line options and configuration files use the same option
sections and grouping.
Configuration file section names are listed in the command line option
sections below.
Option names and values are the same for both command line
and configuration file specification.
.PP
Options specified are the combined set of command line parameters and
configuration file parameters.
Duplicated options will result in a respecification error, regardless of the
location they were specified at.
.TP
.BI \-c " configuration_file_option"
This option specifies the files that mkfs configuration will be obtained from.
The valid
.I configuration_file_option
is:
.RS 1.2i
.TP
.BI options= name
The configuration options will be sourced from the file specified by the
.I name
option string.
This option can be use either an absolute or relative path to the configuration
file to be read.
Sample configuration files can be found in @mkfs_cfg_dir@.
.RE
.PP
.PD 0
.BI \-b " block_size_options"
.TP
.BI "Section Name: " [block]
.PD
This option specifies the fundamental block size of the filesystem.
The valid
.I block_size_option
is:
.RS 1.2i
.TP
.BI size= value
The filesystem block size is specified with a
.I value
in bytes. The default value is 4096 bytes (4 KiB), the minimum is 512, and the
maximum is 65536 (64 KiB).
.IP
Although
.B mkfs.xfs
will accept any of these values and create a valid filesystem,
XFS on Linux can only mount filesystems with pagesize or smaller blocks.
.RE
.PP
.PD 0
.BI \-m " global_metadata_options"
.TP
.BI "Section Name: " [metadata]
.PD
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
.I global_metadata_options
are:
.RS 1.2i
.TP
.BI bigtime= value
This option enables filesystems that can handle inode timestamps from December
1901 to July 2486, and quota timer expirations from January 1970 to July 2486.
The value is either 0 to disable the feature, or 1 to enable large timestamps.
.IP
If this feature is not enabled, the filesystem can only handle timestamps from
December 1901 to January 2038, and quota timers from January 1970 to February
2106.
.IP
By default,
.B mkfs.xfs
will enable this feature.
If the option
.B \-m crc=0
is used, the large timestamp feature is not supported and is disabled.
.TP
.BI 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.
.IP
CRCs enable enhanced error detection due to hardware issues, whilst the format
changes also improves crash recovery algorithms and the ability of various tools
to validate and repair metadata corruptions when they are found.  The CRC
algorithm used is CRC32c, so the overhead is dependent on CPU architecture as
some CPUs have hardware acceleration of this algorithm.  Typically the overhead
of calculating and checking the CRCs is not noticeable in normal operation.
.IP
By default,
.B mkfs.xfs
will enable metadata CRCs.
.IP
Formatting a filesystem without CRCs selects the V4 format, which is deprecated
and will be removed from upstream in September 2030.
Distributors may choose to withdraw support for the V4 format earlier than
this date.
Several other options, noted below, are only tunable on V4 formats, and will
be removed along with the V4 format itself.
.TP
.BI 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.
.IP
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.
.IP
By default,
.B mkfs.xfs
will create free inode btrees for filesystems created with the (default)
.B \-m crc=1
option set. When the option
.B \-m crc=0
is used, the free inode btree feature is not supported and is disabled.
.TP
.BI inobtcount= value
This option causes the filesystem to record the number of blocks used by
the inode btree and the free inode btree.
This can be used to reduce mount times when the free inode btree is enabled.
.IP
By default,
.B mkfs.xfs
will enable this option.
This feature is only available for filesystems created with the (default)
.B \-m finobt=1
option set.
When the option
.B \-m finobt=0
is used, the inode btree counter feature is not supported and is disabled.
.TP
.BI uuid= value
Use the given value as the filesystem UUID for the newly created filesystem.
The default is to generate a random UUID.
.TP
.BI rmapbt= value
This option enables the creation of a reverse-mapping btree index in each
allocation group.  The value is either 0 to disable the feature, or 1 to
create the btree.
.IP
The reverse mapping btree maps filesystem blocks to the owner of the
filesystem block.  Most of the mappings will be to an inode number and an
offset, though there will also be mappings to filesystem metadata.  This
secondary metadata can be used to validate the primary metadata or to
pinpoint exactly which data has been lost when a disk error occurs.
.IP
By default,
.B mkfs.xfs
will create reverse mapping btrees when possible.
This feature is only available for filesystems created with the (default)
.B \-m crc=1
option set. When the option
.B \-m crc=0
is used, the reverse mapping btree feature is not supported and is disabled.
.TP
.BI reflink= value
This option enables the use of a separate reference count btree index in each
allocation group. The value is either 0 to disable the feature, or 1 to create
a reference count btree in each allocation group.
.IP
The reference count btree enables the sharing of physical extents between
the data forks of different files, which is commonly known as "reflink".
Unlike traditional Unix filesystems which assume that every inode and
logical block pair map to a unique physical block, a reflink-capable
XFS filesystem removes the uniqueness requirement, allowing up to four
billion arbitrary inode/logical block pairs to map to a physical block.
If a program tries to write to a multiply-referenced block in a file, the write
will be redirected to a new block, and that file's logical-to-physical
mapping will be changed to the new block ("copy on write").  This feature
enables the creation of per-file snapshots and deduplication.  It is only
available for the data forks of regular files.
.IP
By default,
.B mkfs.xfs
will create reference count btrees and therefore will enable the
reflink feature.  This feature is only available for filesystems created with
the (default)
.B \-m crc=1
option set. When the option
.B \-m crc=0
is used, the reference count btree feature is not supported and reflink is
disabled.
.RE
.PP
.PD 0
.BI \-d " data_section_options"
.TP
.BI "Section Name: " [data]
.PD
These options specify the location, size, and other parameters of the
data section of the filesystem. The valid
.I data_section_options
are:
.RS 1.2i
.TP
.BI agcount= value
This is used to specify the number of allocation groups. The data section
of the filesystem is divided into allocation groups to improve the
performance of XFS. More allocation groups imply that more parallelism
can be achieved when allocating blocks and inodes. The minimum
allocation group size is 16 MiB; the maximum size is just under 1 TiB.
The data section of the filesystem is divided into
.I value
allocation groups (default value is scaled automatically based
on the underlying device size).
.TP
.BI agsize= value
This is an alternative to using the
.B agcount
suboption. The
.I value
is the desired size of the allocation group expressed in bytes
(usually using the
.BR 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
.B agcount
and
.B agsize
suboptions are mutually exclusive.
.TP
.BI cowextsize= value
Set the copy-on-write extent size hint on all inodes created by
.BR mkfs.xfs "."
The value must be provided in units of filesystem blocks.
If the value is zero, the default value (currently 32 blocks) will be used.
Directories will pass on this hint to newly created regular files and
directories.
.TP
.BI 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
.B internal
(with a size, see the
.B \-l
option below) and there can be no real-time section.
.TP
.BI file[= value ]
This is used to specify that the file given by the
.B name
suboption is a regular file. The
.I 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
.I value
is omitted then 1 is assumed.
.TP
.BI size= value
This is used to specify the size of the data section. This suboption
is required if
.B \-d file[=1]
is given. Otherwise, it is only needed if the filesystem should occupy
less space than the size of the special file.

The data section must be at least 300MB in size.
.TP
.BI sunit= value
This is used to specify the stripe unit for a RAID device or a
logical volume. The
.I value
has to be specified in 512-byte block units. Use the
.B 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.
.TP
.BI su= value
This is an alternative to using
.B sunit.
The
.B su
suboption is used to specify the stripe unit for a RAID device or a
striped logical volume. The
.I value
has to be specified in bytes, (usually using the
.BR m " or " g
suffixes). This
.I value
must be a multiple of the filesystem block size.
.TP
.BI swidth= value
This is used to specify the stripe width for a RAID device or a
striped logical volume. The
.I value
has to be specified in 512-byte block units. Use the
.B sw
suboption to specify the stripe width size in bytes.
This suboption is required if
.B \-d sunit
has been specified and it has to be a multiple of the
.B \-d sunit
suboption.
.TP
.BI sw= value
suboption is an alternative to using
.B swidth.
The
.B sw
suboption is used to specify the stripe width for a RAID device or
striped logical volume. The
.I 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.
.IP
When a filesystem is created on a block device,
.B mkfs.xfs
will automatically query the block device for appropriate
.B sunit
and
.B swidth
values if the block device and the filesystem size would be larger than 1GB.
.TP
.BI noalign
This option disables automatic geometry detection and creates the filesystem
without stripe geometry alignment even if the underlying storage device provides
this information.
.TP
.BI rtinherit= value
If
.I value
is set to 1, all inodes created by
.B mkfs.xfs
will be created with the realtime flag set.
The default is 0.
Directories will pass on this flag to newly created regular files and
directories.
.TP
.BI projinherit= value
All inodes created by
.B mkfs.xfs
will be assigned the project quota id provided in
.I value.
Directories will pass on the project id to newly created regular files and
directories.
.TP
.BI extszinherit= value
All inodes created by
.B mkfs.xfs
will have this
.I value
extent size hint applied.
The value must be provided in units of filesystem blocks.
Directories will pass on this hint to newly created regular files and
directories.
.TP
.BI daxinherit= value
If
.I value
is set to 1, all inodes created by
.B mkfs.xfs
will be created with the DAX flag set.
The default is 0.
Directories will pass on this flag to newly created regular files and
directories.
By default,
.B mkfs.xfs
will not enable DAX mode.
.TP
.BI concurrency= value
Create enough allocation groups to handle the desired level of concurrency.
The goal of this calculation scheme is to set the number of allocation groups
to an integer multiple of the number of writer threads desired, to minimize
contention of AG locks.
This scheme will neither create fewer AGs than would be created by the default
configuration, nor will it create AGs smaller than 4GB.
This option is not compatible with the
.B agcount
or
.B agsize
options.
The magic value
.I nr_cpus
or
.I 1
or no value at all will set this parameter to the number of active processors
in the system.
If the kernel advertises that the data device is a non-mechanical storage
device,
.B mkfs.xfs
will use this new geometry calculation scheme.
The magic value of
.I 0
forces use of the older AG geometry calculations that is used for mechanical
storage.
.RE
.TP
.B \-f
Force overwrite when an existing filesystem is detected on the device.
By default,
.B mkfs.xfs
will not write to the device if it suspects that there is a filesystem
or partition table on the device already.
.PP
.PD 0
.BI \-i " inode_options"
.TP
.BI "Section Name: " [inode]
.PD
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.
.IP
The valid
.I inode_options
are:
.RS 1.2i
.TP
.BI size= value " | perblock=" value
The inode size is specified either as a
.I value
in bytes with
.BR size=
or as the number fitting in a filesystem block with
.BR perblock= .
The minimum (and default)
.I value
is 256 bytes without crc, 512 bytes with crc enabled.
The maximum
.I value
is 2048 (2 KiB) subject to the restriction that
the inode size cannot exceed one half of the filesystem block size.
.IP
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,
.B 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,
.B mkfs.xfs
will warn if this will create inode numbers > 32 significant
bits.
.TP
.BI maxpct= value
This specifies the maximum percentage of space in the filesystem that
can be allocated to inodes. The default
.I value
is 25% for filesystems under 1TB, 5% for filesystems under 50TB and 1%
for filesystems over 50TB.
.IP
Setting the value to 0 means that essentially all of the filesystem
can become inode blocks (subject to possible
.B inode32
mount option restrictions, see
.BR xfs (5)
for details.)
.IP
This value can be modified with
.BR xfs_growfs (8).
.TP
.BI align[= value ]
This is used to specify that inode allocation is or is not aligned. The
.I value
is either 0 or 1, with 1 signifying that inodes are allocated aligned.
If the
.I 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).
.IP
This option is only tunable on the deprecated V4 format.
.TP
.BI attr= value
This is used to specify the version of extended attribute inline
allocation policy to be used.  By default, this is 2, which uses an
efficient algorithm for managing the available inline inode space
between attribute and extent data.
.IP
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.
.IP
This option is only tunable on the deprecated V4 format.
.TP
.BI projid32bit[= value ]
This is used to enable 32bit quota project identifiers. The
.I 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.)
.IP
This option is only tunable on the deprecated V4 format.
.TP
.BI sparse[= value ]
Enable sparse inode chunk allocation. The
.I value
is either 0 or 1, with 1 signifying that sparse allocation is enabled.
If the value is omitted, 1 is assumed. Sparse inode allocation is
enabled by default. This feature is only available for filesystems
formatted with
.B \-m crc=1.
.IP
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.
.TP
.BI nrext64[= value]
Extend maximum values of inode data and attr fork extent counters from 2^31 -
1 and 2^15 - 1 to 2^48 - 1 and 2^32 - 1 respectively.
If the value is omitted, 1 is assumed.
This feature will be enabled when possible.
This feature is only available for filesystems formatted with -m crc=1.
.TP
.RE
.PP
.PD 0
.BI \-l " log_section_options"
.TP
.BI "Section Name: " [log]
.PD
These options specify the location, size, and other parameters of the
log section of the filesystem. The valid
.I log_section_options
are:
.RS 1.2i
.TP
.BI agnum= value
If the log is internal, allocate it in this AG.
.TP
.BI 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
.I value
is either 0 or 1, with 1 signifying that the log is internal. If the
.I value
is omitted, 1 is assumed.
.TP
.BI logdev= device
This is used to specify that the log section should reside on the
.I device
separate from the data section. The
.B internal=1
and
.B logdev
options are mutually exclusive.
.TP
.BI size= value
This is used to specify the size of the log section.
.IP
If the log is contained within the data section and
.B size
isn't specified,
.B 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.
.IP
Otherwise, the
.B size
suboption is only needed if the log section of the filesystem
should occupy less space than the size of the special file. The
.I value
is specified in bytes or blocks, with a
.B 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.

The log must be at least 64MB in size.
The log cannot be more than 2GB in size.
.TP
.BI 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).
.IP
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.
.IP
This option is only tunable on the deprecated V4 format.
.TP
.BI sunit= value
This specifies the alignment to be used for log writes. The
.I value
has to be specified in 512-byte block units. Use the
.B 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
.B 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
.B sunit
suboption is specified.
.IP
The
.B su
suboption is an alternative to using
.B sunit.
.TP
.BI su= value
This is used to specify the log stripe. The
.I value
has to be specified in bytes, (usually using the
.BR s " or " b
suffixes). This value must be a multiple of the filesystem block size.
Version 2 logs are automatically selected if the log
.B su
suboption is specified.
.TP
.BI 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
.I value
can be either 0 or 1.
.IP
With
.BR 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
.I value
is 1 (on) so you must specify
.B lazy-count=0
if you want to disable this feature for older kernels which don't support
it.
.IP
This option is only tunable on the deprecated V4 format.
.TP
.BI concurrency= value
Allocate a log that is estimated to be large enough to handle the desired level
of concurrency without userspace program threads contending for log space.
This scheme will neither create a log smaller than the minimum required,
nor create a log larger than the maximum possible.
This option is only valid for internal logs and is not compatible with the
size option.
This option is not compatible with the
.B logdev
or
.B size
options.
The magic value
.I nr_cpus
or
.I 1
or no value at all will set this parameter to the number of active processors
in the system.
.RE
.PP
.PD 0
.BI \-n " naming_options"
.TP
.BI "Section Name: " [naming]
.PD
These options specify the version and size parameters for the naming
(directory) area of the filesystem. The valid
.I naming_options
are:
.RS 1.2i
.TP
.BI size= value
The directory block size is specified with a
.I value
in bytes.  The block size must be a power of 2 and cannot be less than the
filesystem block size.
The default size
.I value
for version 2 directories is 4096 bytes (4 KiB),
unless the filesystem block size is larger than 4096,
in which case the default
.I value
is the filesystem block size.
For version 1 directories the block size is the same as the
filesystem block size.
.TP
.BI version= value
The naming (directory) version
.I value
can be either 2 or 'ci', defaulting to 2 if unspecified.
With version 2 directories, the directory block size can be
any power of 2 size from the filesystem block size up to 65536.
.IP
If the
.B version=ci
option is specified, the kernel will transform certain bytes in filenames
before performing lookup-related operations.
The byte sequence given to create a directory entry is persisted without
alterations.
The lookup transformations are defined as follows:

    0x41-0x5a -> 0x61-0x7a

    0xc0-0xd6 -> 0xe0-0xf6

    0xd8-0xde -> 0xf8-0xfe

This transformation roughly corresponds to case insensitivity in ISO
8859-1.
The transformations are not compatible with other encodings (e.g. UTF8).
Do not enable this feature unless your entire environment has been coerced
to ISO 8859-1.
This feature is deprecated and will be removed in September 2030.
.IP
Note: Version 1 directories are not supported.
.TP
.BI ftype= value
This feature allows the inode type to be stored in the directory
structure so that the
.BR readdir (3)
and
.BR getdents (2)
do not need to look up the inode to determine the inode type.

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

When CRCs are enabled (the default), the ftype functionality is always
enabled, and cannot be turned off.
.IP
In other words, this option is only tunable on the deprecated V4 format.
.RE
.PP
.PD 0
.TP
.BI \-p " protofile_options"
.TP
.BI "Section Name: " [proto]
.PD
These options specify the protofile parameters for populating the filesystem.
The valid
.I protofile_options
are:
.RS 1.2i
.TP
.BI [file=] protofile
The
.B file=
prefix is not required for this CLI argument for legacy reasons.
If specified as a config file directive, the prefix is required.

If the optional
.PD
.I protofile
argument is given,
.B mkfs.xfs
uses
.I protofile
as a prototype file and takes its directions from that file.
The blocks and inodes specifiers in the
.I 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.
.nf
.sp .8v
.in +5
\f71       /stand/\f1\f2diskboot\f1\f7
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      $\f1
.in -5
.fi
.IP
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.
.IP
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.
.IP
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.
.IP
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.
.IP
Notice the dollar sign
.RB ( $ )
syntax on line 7. This syntax directs the
.B 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
.B $
on lines 13 and 14 end the process, since no additional
specifications follow.
.IP
File specifications provide the following:
.IP
  * file mode
.br
  * user ID
.br
  * group ID
.br
  * the file's beginning contents
.P
.IP
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
.B \-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
.BR u .
If setuserID mode is not specified, the second character is
.BR \- .
The third character of the mode string is
used to specify the setgroupID mode, in which
case it is
.BR g .
If setgroupID mode is not specified, the third character is
.BR \- .
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
.BR chmod (1)
command.
.IP
Following the mode character string are two
decimal number tokens that specify the user and group IDs
of the file's owner.
.IP
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
.B mkfs.xfs
command creates the entries
.B dot
(.) and
.B 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 (
.B $
) token.
.TP
.BI slashes_are_spaces= value
If set to 1, slashes ("/") in the first token of each line of the protofile
are converted to spaces.
This enables the creation of a filesystem containing filenames with spaces.
By default, this is set to 0.
.RE
.TP
.B \-q
Quiet option. Normally
.B mkfs.xfs
prints the parameters of the filesystem
to be constructed;
the
.B \-q
flag suppresses this.
.PP
.PD 0
.BI \-r " realtime_section_options"
.TP
.BI "Section Name: " [realtime]
.PD
These options specify the location, size, and other parameters of the
real-time section of the filesystem. The valid
.I realtime_section_options
are:
.RS 1.2i
.TP
.BI rtdev= device
This is used to specify the
.I device
which should contain the real-time section of the filesystem.
The suboption value is the name of a block device.
.TP
.BI extsize= value
This is used to specify the size of the blocks in the real-time
section of the filesystem. This
.I 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.
.TP
.BI size= value
This is used to specify the size of the real-time section.
This suboption is only needed if the real-time section of the
filesystem should occupy less space than the size of the partition
or logical volume containing the section.
.TP
.BI noalign
This option disables stripe size detection, enforcing a realtime device with no
stripe geometry.
.RE
.PP
.PD 0
.BI \-s " sector_size_options"
.TP
.BI "Section Name: " [sector]
.PD
This option specifies the fundamental sector size of the filesystem.
The valid
.I sector_size_option
is:
.RS 1.2i
.TP
.BI size= value
The sector size is specified with a
.I value
in bytes.  The default
.I sector_size
is 512 bytes. The minimum value for sector size is
512; the maximum is 32768 (32 KiB). The
.I sector_size
must be a power of 2 size and cannot be made larger than the
filesystem block size.
.RE
.TP
.BI \-L " label"
Set the filesystem
.IR label .
XFS filesystem labels can be at most 12 characters long; if
.I label
is longer than 12 characters,
.B mkfs.xfs
will not proceed with creating the filesystem.  Refer to the
.BR mount "(8) and " xfs_admin (8)
manual entries for additional information.
.TP
.B \-N
Causes the file system parameters to be printed out without really
creating the file system.
.TP
.B \-K
Do not attempt to discard blocks at mkfs time.
.TP
.B \-V
Prints the version number and exits.
.SH Configuration File Format
The configuration file uses a basic INI format to specify sections and options
within a section.
Section and option names are case sensitive.
Section names must not contain whitespace.
Options are name-value pairs, ended by the first whitespace in the line.
Option names cannot contain whitespace.
Full line comments can be added by starting a line with a # symbol.
If values contain whitespace, then it must be quoted.
.PP
The following example configuration file sets the block size to 4096 bytes,
turns on reverse mapping btrees and sets the inode size to 2048 bytes.
.PP
.PD 0
# Example mkfs.xfs configuration file
.HP
.HP
[block]
.HP
size=4k
.HP
.HP
[metadata]
.HP
rmapbt=1
.HP
.HP
[inode]
.HP
size=2048
.HP
.PD
.PP
.SH SEE ALSO
.BR xfs (5),
.BR mkfs (8),
.BR mount (8),
.BR xfs_info (8),
.BR xfs_admin (8).
.SH BUGS
With a prototype file, it is not possible to specify hard links.