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:
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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:
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mkfs.xfs -l logdev=/dev/sdb1,size=10000b /dev/sda1 |
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Each of the
option elements in the argument list above can be given as multiple comma-separated
suboptions if multiple suboptions apply to the same option.
Equivalently, each main option can be given multiple times with
different suboptions.
For example,
-l internal,size=10000b and
-l internal -l size=10000b are equivalent.
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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:
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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). |
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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).
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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When a filesystem is created on a logical volume device,
mkfs.xfs will automatically query the logical volume for appropriate
sunit and
swidth values.
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-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.
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-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.
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The valid
inode_options are:
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size=value | log=value | perblock=value |
| The inode size is specified either as a
value in bytes with
size=, a base two logarithm
value with
log=, or as the number fitting in a filesystem block with
perblock=. The mininum (and default)
value is 256 bytes.
The maximum
value is 2048 (2 KiB) subject to the restriction that
the inode size cannot exceed one half of the filesystem block size.
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XFS uses 64-bit inode numbers internally; however, the number of
significant bits in an inode number
is affected by filesystem geometry. In
practice, filesystem size and inode size are the predominant factors.
The Linux kernel (on 32 bit hardware platforms) and most applications
cannot currently handle inode numbers greater than 32 significant bits,
so if no inode size is given on the command line,
mkfs.xfs will attempt to choose a size
such that inode numbers will be < 32 bits. If an inode size
is specified, or if a filesystem is sufficently large,
mkfs.xfs will warn if this will create inode numbers > 32 significant
bits.
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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.
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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).
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Setting the value to 0 means that essentially all of the filesystem
can become inode blocks, subject to inode32 restrictions.
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This value can be modified with
xfs_growfs(8) .
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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).
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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.
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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.
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-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:
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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.
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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.
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size=value |
| This is used to specify the size of the log section.
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If the log is contained within the data section and
size isnt 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.
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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.
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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).
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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.
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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.
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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.
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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 serialisation point in the filesystem. The
value can be either 0 or 1.
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With
lazy-count=1, the superblock is not modified or logged on every change of the
persistent counters. Instead, enough information is kept in
other parts of the filesystem to be able to maintain the persistent
counter values without needed to keep them in the superblock.
This gives significant improvements in performance on some configurations.
The default
value is 0 (off) so you must specify
lazy-count=1 if you want to make use of this feature.
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-n naming_options |
| These options specify the version and size parameters for the naming
(directory) area of the filesystem. The valid
naming_options are:
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size=value | log=value |
| The block size is specified either as a
value in bytes with
size=, or as a base two logarithm
value with log=. The default size
value for version 2 directories is 4096 bytes (4 KiB),
unless the filesystem block size is larger than 4096,
in which case the default
value is the filesystem block size.
For version 1 directories the block size is the same as the
filesystem block size.
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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.
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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.
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Note: Version 1 directories are not supported.
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-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 $
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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.
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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.
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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.
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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.
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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.
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File specifications provide the following:
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* file mode
* user ID
* group ID
* the files beginning contents
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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.
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Following the mode character string are two
decimal number tokens that specify the user and group IDs
of the files owner.
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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.
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-q | Quiet option. Normally
mkfs.xfs prints the parameters of the filesystem
to be constructed;
the
-q flag suppresses this.
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-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:
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