Ubuntu Manpage: mkfs.xfs - construct an XFS filesystem

Provided by: xfsprogs_5.3.0-1ubuntu2.1_amd64

NAME

       mkfs.xfs - construct an XFS filesystem

SYNOPSIS

       mkfs.xfs [ -b block_size_options ] [ -m global_metadata_options ] [ -d data_section_options ] [ -f ] [ -i
       inode_options ] [ -l log_section_options ] [  -n  naming_options  ]  [  -p  protofile  ]  [  -q  ]  [  -r
       realtime_section_options ] [ -s sector_size_options ] [ -L label ] [ -N ] [ -K ] device
       mkfs.xfs -V

DESCRIPTION

mkfs.xfs constructs an XFS filesystem by writing on a special file using the values found in the
arguments of the command line. It is invoked automatically by mkfs(8) when it is given the -t xfs
option.

In its simplest (and most commonly used form), the size of the filesystem is determined from the disk
driver. As an example, to make a filesystem with an internal log on the first partition on the first
SCSI disk, use:

mkfs.xfs /dev/sda1

The metadata log can be placed on another device to reduce the number of disk seeks. To create a
filesystem on the first partition on the first SCSI disk with a 10MiB log located on the first partition
on the second SCSI disk, use:

mkfs.xfs -l logdev=/dev/sdb1,size=10m /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=10m and -l internal -l size=10m
are equivalent.

In the descriptions below, sizes are given in sectors, bytes, blocks, kilobytes, megabytes, gigabytes,
etc. Sizes are treated as hexadecimal if prefixed by 0x or 0X, octal if prefixed by 0, or decimal
otherwise. The following lists possible multiplication suffixes:
s - multiply by sector size (default = 512, see -s option below).
b - multiply by filesystem block size (default = 4K, see -b option below).
k - multiply by one kilobyte (1,024 bytes).
m - multiply by one megabyte (1,048,576 bytes).
g - multiply by one gigabyte (1,073,741,824 bytes).
t - multiply by one terabyte (1,099,511,627,776 bytes).
p - multiply by one petabyte (1,024 terabytes).
e - multiply by one exabyte (1,048,576 terabytes).

When specifying parameters in units of sectors or filesystem blocks, the -s option or the -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.

Many feature options allow an optional argument of 0 or 1, to explicitly disable or enable the
functionality.

OPTIONS

-b block_size_options
This option specifies the fundamental block size of the filesystem. The valid block_size_option
is:

size=value
The filesystem block size is specified with a value in bytes. The default value is
4096 bytes (4 KiB), the minimum is 512, and the maximum is 65536 (64 KiB).

Although 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.

-m global_metadata_options
These options specify metadata format options that either apply to the entire filesystem or aren't
easily characterised by a specific functionality group. The valid global_metadata_options are:

crc=value
This is used to create a filesystem which maintains and checks CRC information in all
metadata objects on disk. The value is either 0 to disable the feature, or 1 to enable
the use of CRCs.

CRCs enable enhanced error detection due to hardware issues, whilst the format changes
also improves crash recovery algorithms and the ability of various tools to validate
and repair metadata corruptions when they are found. The CRC algorithm used is
CRC32c, so the overhead is 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.

By default, mkfs.xfs will enable metadata CRCs.

finobt=value
This option enables the use of a separate free inode btree index in each allocation
group. The value is either 0 to disable the feature, or 1 to create a free inode btree
in each allocation group.

The free inode btree mirrors the existing allocated inode btree index which indexes
both used and free inodes. The free inode btree does not index used inodes, allowing
faster, more consistent inode allocation performance as filesystems age.

By default, mkfs.xfs will create free inode btrees for filesystems 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 is disabled.

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

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.

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.

By default, mkfs.xfs will not create reverse mapping btrees. This feature is only
available for filesystems created with the (default) -m crc=1 option set. When the
option -m crc=0 is used, the reverse mapping btree feature is not supported and is
disabled.

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.

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.

By default, 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) -m crc=1 option set. When the option -m crc=0 is used, the reference count
btree feature is not supported and reflink is disabled.

Note: the filesystem DAX mount option ( -o dax ) is incompatible with reflink-enabled
XFS filesystems. To use filesystem DAX with XFS, specify the -m reflink=0 option to
mkfs.xfs to disable the reflink feature.

-d data_section_options
These options specify the location, size, and other parameters of the data section of the
filesystem. The valid data_section_options are:

agcount=value
This is used to specify the number of allocation groups. The data 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 size).

agsize=value
This is an alternative to using the agcount suboption. The value is the desired size
of the allocation group expressed in bytes (usually using the m or g suffixes). This
value must be a multiple of the filesystem block size, and must be at least 16MiB, and
no more than 1TiB, and may be automatically adjusted to properly align with the stripe
geometry. The agcount and agsize suboptions are mutually exclusive.

cowextsize=value
Set the copy-on-write extent size hint on all inodes created by 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 children.

name=value
This can be used to specify the name of the special file containing the filesystem. In
this case, the log section must be specified as internal (with a size, see the -l
option below) and there can be no real-time section.

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

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

sunit=value
This is used to specify the stripe unit for a RAID device or a logical volume. The
value has to be specified in 512-byte block units. Use the su suboption to specify the
stripe unit size in bytes. This suboption ensures that data allocations will be stripe
unit aligned when the 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.

su=value
This is an alternative to using sunit. The su suboption is used to specify the stripe
unit for a RAID device or a striped logical volume. The value has to be specified in
bytes, (usually using the m or g suffixes). This value must be a multiple of the
filesystem block size.

swidth=value
This is used to specify the stripe width for a RAID device or a striped logical
volume. The value has to be specified in 512-byte block units. Use the sw suboption to
specify the stripe width size in bytes. This suboption is required if -d sunit has
been specified and it has to be a multiple of the -d sunit suboption.

sw=value
suboption is an alternative to using swidth. The sw suboption is used to specify the
stripe width for a RAID device or striped logical 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.

noalign
This option disables automatic geometry detection and creates the filesystem without
stripe geometry alignment even if the underlying storage device provides this
information.

rtinherit=value
If set, all inodes created by mkfs.xfs will be created with the realtime flag set.
Directories will pass on this flag to newly created children.

projinherit=value
All inodes created by mkfs.xfs will be assigned this project quota id. Directories
will pass on the project id to newly created children.

extszinherit=value
All inodes created by mkfs.xfs will have this extent size hint applied. The value
must be provided in units of filesystem blocks. Directories will pass on this hint to
newly created children.

-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: 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 | perblock=value
The inode size is specified either as a value in bytes with size= or as the number
fitting in a filesystem block with perblock=. The minimum (and default) value is 256
bytes without crc, 512 bytes with crc enabled. 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 significant bits.

maxpct=value
This specifies the maximum percentage of space in the filesystem that can be allocated
to inodes. The default value is 25% for filesystems under 1TB, 5% for filesystems
under 50TB and 1% for filesystems over 50TB.

In the default inode allocation mode, inode blocks are chosen such that inode numbers
will not exceed 32 bits, which restricts the inode blocks to the lower portion of the
filesystem. The data block allocator will avoid these low blocks to accommodate the
specified maxpct, so a high value may result in a filesystem with nothing but inodes
in a 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
platforms).

Setting the value to 0 means that essentially all of the filesystem can become inode
blocks, subject to inode32 restrictions.

This value can be modified with xfs_growfs(8).

align[=value]
This is used to specify that inode allocation is or is not aligned. The value is
either 0 or 1, with 1 signifying that inodes are allocated aligned. If the value is
omitted, 1 is assumed. The default is that inodes are aligned. Aligned inode access
is normally more efficient than unaligned access; alignment must be established at the
time the filesystem is created, since inodes are allocated at that time. This option
can be used to turn off inode alignment when the filesystem needs to be mountable by a
version of IRIX that does not have the inode alignment feature (any release of IRIX
before 6.2, and IRIX 6.2 without XFS patches).

attr=value
This is used to specify the version of extended attribute inline 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 2.6.16.

projid32bit[=value]
This is used to enable 32bit quota project identifiers. The value is either 0 or 1,
with 1 signifying that 32bit projid are to be enabled. If the value is omitted, 1 is
assumed. (This default changed in release version 3.2.0.)

sparse[=value]
Enable sparse inode chunk allocation. The value is either 0 or 1, with 1 signifying
that sparse allocation is enabled. If the value is omitted, 1 is assumed. Sparse
inode allocation is disabled by default. This feature is only available for
filesystems formatted with -m crc=1.

When enabled, sparse inode allocation allows the filesystem to allocate smaller than
the standard 64-inode chunk when free space is severely limited. This feature is
useful for filesystems that might fragment free space over time such that no free
extents are large enough to accommodate a chunk of 64 inodes. Without this feature
enabled, inode allocations can fail with out of space errors under severe fragmented
free space conditions.

-l log_section_options
These options specify the location, size, and other parameters of the log section of the
filesystem. The valid log_section_options are:

agnum=value
If the log is internal, allocate it in this AG.

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

logdev=device
This is used to specify that the log section should reside on the device separate from
the data section. The internal=1 and logdev options are mutually exclusive.

size=value
This is used to specify the size of the log section.

If the log is contained within the data section and size isn't 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.

version=value
This specifies the version of the log. The current default is 2, which allows for
larger log buffer sizes, as well as supporting stripe-aligned log writes (see the
sunit and su options, below).

The previous version 1, which is limited to 32k log buffers and does not support
stripe-aligned writes, is kept for backwards compatibility with very old 2.4 kernels.

sunit=value
This specifies the alignment to be used for log writes. The value has to be specified
in 512-byte block units. Use the su suboption to 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.

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

lazy-count=value
This changes the method of logging various persistent counters in the superblock.
Under metadata intensive workloads, these counters are updated and logged frequently
enough that the superblock updates become a serialization point in the filesystem. The
value can be either 0 or 1.

With lazy-count=1, the superblock is not modified or logged on every change of the
persistent counters. Instead, enough information is kept in other parts of the
filesystem to be able to maintain the persistent counter values without needed to keep
them in the superblock. This gives significant improvements in performance on some
configurations. The default value is 1 (on) so you must specify lazy-count=0 if you
want to disable this feature for older kernels which don't support it.

-n naming_options
These options specify the version and size parameters for the naming (directory) area of the
filesystem. The valid naming_options are:

size=value
The directory block size is specified with a value in bytes. The block size must be a
power of 2 and cannot be less than the filesystem block size. The default size value
for version 2 directories is 4096 bytes (4 KiB), unless the filesystem block size is
larger than 4096, in which case the default value is the filesystem block size. For
version 1 directories the block size is the same as the filesystem block size.

version=value
The naming (directory) version value can be either 2 or 'ci', 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 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 with.

Note: Version 1 directories are not supported.

ftype=value
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 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.

-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
7 $
8 b0 b--644 3 1 0 0
9 c0 c--644 3 1 0 0
10 fifo p--644 3 1
11 slink l--644 3 1 /a/symbolic/link
12 : This is a comment line
13 $
14 $

Line 1 is a dummy string. (It was formerly the bootfilename.) It is present for backward
compatibility; boot blocks are not used on SGI systems.

Note that some string of characters must be present as the first line of the proto file to cause
it to be parsed correctly; the value of this string is immaterial since it is ignored.

Line 2 contains two numeric values (formerly the numbers of blocks and inodes). These are also
merely for backward compatibility: two numeric values must appear at this point for the proto file
to be correctly parsed, but their values are 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 follow.

File specifications provide the following:

* file mode
* user ID
* group ID
* the file's beginning contents

A 6-character string defines the mode for a file. The first character of this string defines the
file type. The character range for this first character is -bcdpl. A file may be a regular file,
a block special file, a character special file, directory files, named pipes (first-in, first out
files), and symbolic links. The second character of the mode string is used to specify setuserID
mode, in which case it is u. If setuserID mode is not specified, the second character is -. The
third character of the mode string is used to specify the setgroupID mode, in which case it is g.
If setgroupID mode is not specified, the third character is -. The remaining characters of the
mode string are a three digit octal number. This octal number defines the owner, group, and other
read, write, and execute permissions for the file, respectively. For more information on file
permissions, see the chmod(1) command.

Following the mode character string are two decimal number tokens that specify the user and group
IDs of the file's owner.

In a regular file, the next token specifies the pathname from which the contents and size of the
file are copied. In a block or character special file, the next token are two decimal numbers
that specify the major and minor device numbers. When a file is a symbolic link, the next token
specifies the contents of the link.

When the file is a directory, the mkfs.xfs command creates the entries dot (.) and dot-dot (..)
and then reads the list of names and file specifications in a 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 realtime_section_options
These options specify the location, size, and other parameters of the real-time section of the
filesystem. The valid realtime_section_options are:

rtdev=device
This is used to specify the device which should contain the real-time section of the
filesystem. The suboption value is the name of a block device.

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

size=value
This is used to specify the size of the real-time section. This 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.

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

-s sector_size_options
This option specifies the fundamental sector size of the filesystem. The valid sector_size_option
is:

size=value
The sector size is specified with a value in bytes. The default sector_size is 512
bytes. The minimum value for sector size is 512; the maximum is 32768 (32 KiB). The
sector_size must be a power of 2 size and cannot be made larger than the filesystem
block size.

-L label
Set the filesystem label. XFS filesystem labels can be at most 12 characters long; if label is
longer than 12 characters, mkfs.xfs will not proceed with creating the filesystem. Refer to the
mount(8) and xfs_admin(8) manual entries for additional information.

-N Causes the file system parameters to be printed out without really creating the file system.

-K Do not attempt to discard blocks at mkfs time.

-V Prints the version number and exits.

BUGS

       With a prototype file, it is not possible to specify hard links.

                                                                                                     mkfs.xfs(8)

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

SEE ALSO

BUGS