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mkfs.xfs(8) mkfs.xfs(8)
NAME
mkfs.xfs - construct an XFS filesystem
SYNOPSIS
mkfs.xfs [ -b subopt=value ] [ -d subopt[=value] ]
[ -i subopt=value ] [ -l subopt[=value] ] [ -f ]
[ -n subopt[=value] ] [ -p protofile ] [ -q ]
[ -r subopt[=value] ] [ -s subopt[=value] ]
[ -N ] [ -L label ] device
DESCRIPTION
mkfs.xfs constructs an XFS filesystem by writing on a special file
using the values found in the arguments of the command line. It is
invoked automatically by mkfs(8) when mkfs is given the -t xfs option.
In its simplest (and most commonly used form), the size of the filesys-
tem is determined from the disk driver. As an example, to make a
filesystem with an internal log on the first partition on the first
SCSI disk, use:
mkfs.xfs /dev/sda1
The metadata log can be placed on another device to reduce the number
of disk seeks. To create a filesystem on the first partition on the
first SCSI disk with a 10000 block log located on the first partition
on the second SCSI disk, use:
mkfs.xfs -l logdev=/dev/sdb1,size=10000b /dev/sda1
Each of the subopt=value elements in the argument list above can be
given as multiple comma-separated subopt=value suboptions if multiple
suboptions apply to the same option. Equivalently, each main option
can be given multiple times with different suboptions. For example, -l
internal,size=10000b and -l internal -l size=10000b are equivalent.
In the descriptions below, sizes are given in sectors, bytes, blocks,
kilobytes, megabytes, or gigabytes. Sizes are treated as hexadecimal
if prefixed by 0x or 0X, octal if prefixed by 0, or decimal otherwise.
If suffixed with s then the size is converted by multiplying it by the
filesystems sector size (defaults to 512, see -s option below). If
suffixed with b then the size is converted by multiplying it by the
filesystems block size (defaults to 4K, see -b option below). If suf-
fixed with k then the size is converted by multiplying it by 1024. If
suffixed with m then the size is converted by multiplying it by one
megabyte (1024 * 1024 bytes). If suffixed with g then the size is con-
verted by multiplying it by one gigabyte (1024 * 1024 * 1024 bytes).
If suffixed with t then the size is converted by multiplying it by one
terabyte (1024 * 1024 * 1024 * 1024 bytes). If suffixed with p then
the size is converted by multiplying it by one petabyte (1024 * 1024 *
1024 * 1024 * 1024 bytes). If suffixed with e then the size is con-
verted by multiplying it by one exabyte (1024 * 1024 * 1024 * 1024 *
1024 * 1024 bytes).
-b Block size options.
This option specifies the fundamental block size of the filesys-
tem. The valid suboptions are: log=value and size=value; only
one can be supplied. The block size is specified either as a
base two logarithm value with log=, or in bytes with size=. The
default value is 4096 bytes (4 KiB), the minimum is 512, and the
maximum is 65536 (64 KiB). XFS on Linux currently only supports
pagesize or smaller blocks.
-d Data section options.
These options specify the location, size, and other parameters
of the data section of the filesystem. The valid suboptions
are: agcount=value, agsize=value, file[=value], name=value,
size=value, sunit=value, swidth=value, su=value, sw=value, and
unwritten[=value].
The agcount suboption is used to specify the number of alloca-
tion groups. The data section of the filesystem is divided into
allocation groups to improve the performance of XFS. More allo-
cation groups imply that more parallelism can be achieved when
allocating blocks and inodes. The minimum allocation group size
is 16 MiB; the maximum size is just under 1 TiB. The data sec-
tion of the filesystem is divided into agcount allocation groups
(default value is scaled automatically based on the underlying
device size). Setting agcount to a very large number should be
avoided, since this causes an unreasonable amount of CPU time to
be used when the filesystem is close to full.
The agsize suboption is an alternative to using agcount. The
argument provided to agsize is the desired size of the alloca-
tion group expressed in bytes (usually using the m or g suf-
fixes). This value must be a multiple of the filesystem block
size, and must be at least 16MiB, and no more than 1TiB, and may
be automatically adjusted to properly align with the stripe
geometry. The agcount suboption and the agsize suboption are
mutually exclusive.
The name suboption can be used to specify the name of the spe-
cial file containing the filesystem. In this case, the log sec-
tion must be specified as internal (with a size, see the -l
option below) and there can be no real-time section.
The file suboption is used to specify that the file given by the
name suboption is a regular file. The suboption value is either
0 or 1, with 1 signifying that the file is regular. This subop-
tion is used only to make a filesystem image. If the value is
omitted then 1 is assumed.
The size suboption is used to specify the size of the data sec-
tion. This suboption is required if -d file[=1] is given. Oth-
erwise, it is only needed if the filesystem should occupy less
space than the size of the special file.
The sunit suboption is used to specify the stripe unit for a
RAID device or a logical volume. The suboption value has to be
specified in 512-byte block units. Use the su suboption to
specify the stripe unit size in bytes. This suboption ensures
that data allocations will be stripe unit aligned when the cur-
rent end of file is being extended and the file size is larger
than 512KiB. Also inode allocations and the internal log will
be stripe unit aligned.
The su suboption is an alternative to using sunit. The su sub-
option is used to specify the stripe unit for a RAID device or a
striped logical volume. The suboption value has to be specified
in bytes, (usually using the m or g suffixes). This value must
be a multiple of the filesystem block size.
The swidth suboption is used to specify the stripe width for a
RAID device or a striped logical volume. The suboption value
has to be specified in 512-byte block units. Use the sw subop-
tion to specify the stripe width size in bytes. This suboption
is required if -d sunit has been specified and it has to be a
multiple of the -d sunit suboption.
The sw suboption is an alternative to using swidth. The sw sub-
option is used to specify the stripe width for a RAID device or
striped logical volume. The suboption value is expressed as a
multiplier of the stripe unit, usually the same as the number of
stripe members in the logical volume configuration, or data
disks in a RAID device.
When a filesystem is created on a logical volume device,
mkfs.xfs will automatically query the logical volume for appro-
priate sunit and swidth values.
The unwritten suboption is used to specify whether unwritten
extents are flagged as such, or not. The suboption value is
either 0 or 1, with 1 signifying that unwritten extent flagging
should occur. If the suboption is omitted, unwritten extent
flagging is enabled. If unwritten extents are flagged, filesys-
tem write performance will be negatively affected for preallo-
cated file extents, since extra filesystem transactions are
required to convert extent flags for the range of the file writ-
ten. This suboption should be disabled if the filesystem needs
to be used on operating system versions which do not support the
flagging capability.
-f Force overwrite when an existing filesystem is detected on the
device. By default, mkfs.xfs will not write to the device if it
suspects that there is a filesystem or partition table on the
device already.
-i Inode options.
This option specifies the inode size of the filesystem, and
other inode allocation parameters. The XFS inode contains a
fixed-size part and a variable-size part. The variable-size
part, whose size is affected by this option, can contain: direc-
tory data, for small directories; attribute data, for small
attribute sets; symbolic link data, for small symbolic links;
the extent list for the file, for files with a small number of
extents; and the root of a tree describing the location of
extents for the file, for files with a large number of extents.
The valid suboptions for specifying inode size are: log=value,
perblock=value, and size=value; only one can be supplied. The
inode size is specified either as a base two logarithm value
with log=, in bytes with size=, or as the number fitting in a
filesystem block with perblock=. The mininum (and default)
value is 256 bytes. The maximum value is 2048 (2 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 plat-
forms) and most applications cannot currently handle inode num-
bers 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 sig-
nificant bits.
The option maxpct=value specifies the maximum percentage of
space in the filesystem that can be allocated to inodes. The
default value is 25%. Setting the value to 0 means that
essentially all of the filesystem can become inode blocks.
The option align[=value] is used to specify that inode alloca-
tion is or is not aligned. The value is either 0 or 1, with 1
signifying that inodes are allocated aligned. If the value is
omitted, 1 is assumed. The default is that inodes are aligned.
Aligned inode access is normally more efficient than unaligned
access; alignment must be established at the time the filesystem
is created, since inodes are allocated at that time. This
option can be used to turn off inode alignment when the filesys-
tem needs to be mountable by a version of IRIX that does not
have the inode alignment feature (any release of IRIX before
6.2, and IRIX 6.2 without XFS patches).
The option attr[=value] 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 filesystem.
-l Log section options.
These options specify the location, size, and other parameters
of the log section of the filesystem. The valid suboptions are:
internal[=value], logdev=device, size=value, version=[1|2],
sunit=value, and su=value.
The internal suboption is used to specify that the log section
is a piece of the data section instead of being another device
or logical volume. The suboption value is either 0 or 1, with 1
signifying that the log is internal. If the value is omitted, 1
is assumed.
The logdev suboption is used to specify that the log section
should reside on a device separate from the data section. The
suboption value is the name of a block device. The internal=1
and logdev options are mutually exclusive.
The size suboption is used to specify the size of the log sec-
tion.
If the log is contained within the data section and size isn't
specified, mkfs.xfs will try to select a suitable log size
depending on the size of the filesystem. The actual logsize
depends on the filesystem block size and the directory block
size.
Otherwise, the size suboption is only needed if the log section
of the filesystem should occupy less space than the size of the
special file. The size is specified in bytes or blocks, with a
b suffix meaning multiplication by the filesystem block size, as
described above. The overriding minimum value for size is 512
blocks. With some combinations of filesystem block size, inode
size, and directory block size, the minimum log size is larger
than 512 blocks.
Using the version suboption to specify a version 2 log enables
the sunit suboption, and allows the logbsize to be increased
beyond 32K. Version 2 logs are automatically selected if a log
stripe unit is specified. See sunit and su suboptions, below.
The sunit suboption specifies the alignment to be used for log
writes. The suboption value has to be specified in 512-byte
block units. Use the su suboption to specify the log stripe
unit size in bytes. Log writes will be aligned on this bound-
ary, and rounded up to this boundary. This gives major improve-
ments in performance on some configurations such as software
raid5 when the sunit is specified as the filesystem block size.
The equivalent byte value must be a multiple of the filesystem
block size. Version 2 logs are automatically selected if the
log su suboption is specified.
The su suboption is an alternative to using sunit. The su sub-
option is used to specify the log stripe. The suboption value
has to be specified in bytes, (usually using the s or b suf-
fixes). This value must be a multiple of the filesystem block
size. Version 2 logs are automatically selected if the log su
suboption is specified.
-n Naming options.
These options specify the version and size parameters for the
naming (directory) area of the filesystem. The valid suboptions
are: log=value, size=value, and version=value. The naming
(directory) version is 1 or 2, defaulting to 2 if unspecified.
With version 2 directories, the directory block size can be any
power of 2 size from the filesystem block size up to 65536. The
block size is specified either as a base two logarithm value
with log=, or in bytes with size=. The default size value for
version 2 directories is 4096 bytes (4 KiB), unless the filesys-
tem block size is larger than 4096, in which case the default
value is the filesystem block size. For version 1 directories
the block size is the same as the filesystem block size.
-p protofile
If the optional -p protofile argument is given, mkfs.xfs uses
protofile as a prototype file and takes its directions from that
file. The blocks and inodes specifiers in the protofile are
provided for backwards compatibility, but are otherwise unused.
The syntax of the protofile is defined by a number of tokens
separated by spaces or newlines. Note that the line numbers are
not part of the syntax but are meant to help you in the follow-
ing discussion of the file contents.
1 /stand/diskboot
2 4872 110
3 d--777 3 1
4 usr d--777 3 1
5 sh ---755 3 1 /bin/sh
6 ken d--755 6 1
7 $
8 b0 b--644 3 1 0 0
9 c0 c--644 3 1 0 0
10 fifo p--644 3 1
11 slink l--644 3 1 /a/symbolic/link
12 : This is a comment line
13 $
14 $
Line 1 is a dummy string. (It was formerly the bootfilename.)
It is present for backward compatibility; boot blocks are not
used on SGI systems.
Note that some string of characters must be present as the first
line of the proto file to cause it to be parsed correctly; the
value of this string is immaterial since it is ignored.
Line 2 contains two numeric values (formerly the numbers of
blocks and inodes). These are also merely for backward compati-
bility: two numeric values must appear at this point for the
proto file to be correctly parsed, but their values are immate-
rial since they are ignored.
The lines 3 through 11 specify the files and directories you
want to include in this filesystem. Line 3 defines the root
directory. Other directories and files that you want in the
filesystem are indicated by lines 4 through 6 and lines 8
through 10. Line 11 contains symbolic link syntax.
Notice the dollar sign ( $ ) syntax on line 7. This syntax
directs the mkfs.xfs command to terminate the branch of the
filesystem it is currently on and then continue from the direc-
tory specified by the next line,in this case line 8 It must be
the last character on a line. The colon on line 12 introduces a
comment; all characters up until the following newline are
ignored. Note that this means you cannot have a file in a pro-
totype file whose name contains a colon. The $ on lines 13 and
14 end the process, since no additional specifications follow.
File specifications provide the following:
* file mode
* user ID
* group ID
* the file's beginning contents
A 6-character string defines the mode for a file. The first
character of this string defines the file type. The character
range for this first character is -bcdpl. A file may be a regu-
lar file, a block special file, a character special file, direc-
tory files, named pipes (first-in, first out files), and sym-
bolic links. The second character of the mode string is used to
specify setuserID mode, in which case it is u. If setuserID
mode is not specified, the second character is -. The third
character of the mode string is used to specify the setgroupID
mode, in which case it is g. If setgroupID mode is not speci-
fied, the second character is -. The remaining characters of
the mode string are a three digit octal number. This octal num-
ber defines the owner, group, and other read, write, and execute
permissions for the file, respectively. Form more information
on file permissions, see the chmod(1) command.
Following the mode character string are two decimal number
tokens that specify the user and group IDs of the file's owner.
In a regular file, the next token specifies the pathname from
which the contents and size of the file are copied. In a block
or character special file, the next token are two decimal num-
bers that specify the major and minor device numbers. When a
file is a symbolic link, the next token specifies the contents
of the link.
When the file is a directory, the mkfs.xfs command creates the
entries dot (.) and dot-dot (..) and then reads the list of
names and file specifications in a recursive manner for all of
the entries in the directory. A scan of the protofile is always
terminated with the dollar ( $ ) token.
-q Quiet option.
Normally mkfs.xfs prints the parameters of the filesystem to be
constructed; the -q flag suppresses this.
-r Real-time section options.
These options specify the location, size, and other parameters
of the real-time section of the filesystem. The valid subop-
tions are: rtdev=device, extsize=value, and size=value.
The rtdev suboption is used to specify the device which should
contain the real-time section of the filesystem. The suboption
value is the name of a block device.
The extsize suboption is used to specify the size of the blocks
in the real-time section of the filesystem. This size must be a
multiple of the filesystem block size. The minimum allowed
value is the filesystem block size or 4 KiB (whichever is
larger); the default value is the stripe width for striped vol-
umes or 64 KiB for non-striped volumes; the maximum allowed
value is 1 GiB. The real-time extent size should be carefully
chosen to match the parameters of the physical media used.
The size suboption is used to specify the size of the real-time
section. This suboption is only needed if the real-time section
of the filesystem should occupy less space than the size of the
partition or logical volume containing the section.
-s Sector size options.
This option specifies the fundamental sector size of the
filesystem. The valid suboptions are: log=value and size=value;
only one can be supplied. The sector size is specified either
as a base two logarithm value with log=, or in bytes with size=.
The default value is 512 bytes. The minimum value for sector
size is 512; the maximum is 32768 (32 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.
SEE ALSO
xfs(5), mkfs(8), mount(8), xfs_info(8), xfs_admin(8).
BUGS
With a prototype file, it is not possible to specify hard links.
mkfs.xfs(8)
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