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mkfs.xfs \- construct an XFS filesystem
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\f3mkfs.xfs\f1 [ \f3\-b\f1 subopt=value ] [ \f3\-d\f1 subopt[=value] ]
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[ \f3\-i\f1 subopt=value ] [ \f3\-l\f1 subopt[=value] ]
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[ \f3\-n\f1 subopt[=value] ] [ \f3\-p\f1 protofile ] [ \f3\-q\f1 ]
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[ \f3\-r\f1 subopt[=value] ] [ \f3\-C\f1 ] [ \f3\-L\f1 label ] device
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constructs an XFS filesystem by writing on a special
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file using the values found in the arguments of the command line.
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It is invoked automatically by \f2mkfs\f1(8) when \f2mkfs\f1 is
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given the \f3\-t xfs\f1 option.
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In its simplest (and most commonly used form), the size of the
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filesystem is determined from the disk driver. As an example, to make
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a filesystem with an internal log on the first partition on the first
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The metadata log can be placed on another device to reduce the number
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of disk seeks. To create a filesystem on the first partition on the
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first SCSI disk with a 10000 block log located on the first partition
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on the second SCSI disk, use:
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mkfs.xfs -l logdev=/dev/sdb1,size=10000b /dev/sda1
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elements in the argument list above can be given as multiple comma-separated
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suboptions if multiple suboptions apply to the same option.
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Equivalently, each main option can be given multiple times with
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.B \-l internal,size=10000b
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.B \-l internal \-l size=10000b
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In the descriptions below, sizes are given in bytes, blocks, kilobytes,
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Sizes are treated as hexadecimal if prefixed by 0x or 0X,
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octal if prefixed by 0, or decimal otherwise.
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If suffixed with \f3b\f1 then the size is converted by multiplying it
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by the filesystem's block size.
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If suffixed with \f3k\f1 then the size is converted by multiplying it by 1024.
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If suffixed with \f3m\f1 then the size is converted by multiplying it by
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1048576 (1024 * 1024).
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If suffixed with \f3g\f1 then the size is converted by multiplying it by
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1073741824 (1024 * 1024 * 1024).
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This option specifies the fundamental block size of the filesystem.
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The valid suboptions are:
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\f3size=\f1\f2value\f1;
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only one can be supplied.
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The block size is specified either as a base two logarithm value with
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The default value is 4096 bytes (4 KB) on systems with a 4KB pagesize.
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The minimum value for block size is 512; the maximum is 65536 (64 KB).
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XFS on Linux currently only supports pagesize blocks.
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These options specify the location, size, and other parameters of the
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data section of the filesystem.
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The valid suboptions are:
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\f3agcount=\f1\f2value\f1,
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\f3agsize=\f1\f2value\f1,
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\f3file\f1[\f3=\f1\f2value\f1],
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\f3name=\f1\f2value\f1,
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\f3size=\f1\f2value\f1,
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\f3sunit=\f1\f2value\f1,
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\f3swidth=\f1\f2value\f1,
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\f3unwritten\f1[\f3=\f1\f2value\f1].
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suboption is used to specify the number of allocation groups.
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The data section of the filesystem is divided into allocation groups
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to improve the performance of XFS.
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More allocation groups imply that more parallelism can be achieved
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when allocating blocks and inodes.
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The minimum allocation group size is 16 MB;
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the maximum size is just under 4 GB.
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The data section of the filesystem is divided into
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allocation groups (default value 8, unless the filesystem is smaller
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than 128 MB or larger than 8 GB).
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to a very large number should be avoided, since this causes an unreasonable
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amount of CPU time to be used when the filesystem is close to full.
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suboption is an alternative to using
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The argument provided to
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is the desired size of the allocation group expressed in bytes
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(usually using the \f3m\f1 or \f3g\f1 suffixes).
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This value must be a multiple of the filesystem block size, and
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must be at least 16MB, and no more than 4GB, and may
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be automatically adjusted to properly align with the stripe geometry.
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suboption are mutually exclusive.
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suboption can be used to specify the name of the special file containing
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In this case, the log section must be specified as
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(with a size, see the
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option below) and there can be no real-time section.
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suboption is used to specify that the file given by the
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suboption is a regular file.
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The suboption value is either 0 or 1,
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with 1 signifying that the file is regular.
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This suboption is used only to make a filesystem image.
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If the value is omitted then 1 is assumed.
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suboption is used to specify the size of the data section.
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This suboption is required if
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Otherwise, it is only needed if the filesystem should occupy
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less space than the size of the special file.
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suboption is used to specify the stripe unit for a RAID device or a
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The suboption value has to be specified in 512-byte block units.
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suboption to specify the stripe unit size in bytes.
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This suboption ensures that data allocations will be stripe unit aligned
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when the current end of file is being extended and the file size is larger
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Also inode allocations and the internal log will be stripe unit aligned.
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suboption is an alternative to using
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suboption is used to specify the stripe unit for a RAID device or a
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striped logical volume.
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The suboption value has to be specified in bytes,
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(usually using the \f3m\f1 or \f3g\f1 suffixes).
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This value must be a multiple of the filesystem block size.
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suboption is used to specify the stripe width for a RAID device or a
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striped logical volume.
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The suboption value has to be specified in 512-byte block units.
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suboption to specify the stripe width size in bytes.
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This suboption is required if
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has been specified and it has to be a multiple of the
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The stripe width will be the preferred iosize returned in the
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suboption is an alternative to using
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suboption is used to specify the stripe width for a RAID device or
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striped logical volume.
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The suboption value is expressed as a multiplier of the stripe unit,
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usually the same as the number of stripe members in the logical
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volume configuration, or data disks in a RAID device.
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When a filesystem is created on a logical volume device,
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will automatically query the logical volume for appropriate
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suboption is used to specify whether unwritten extents are flagged as such,
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The suboption value is either 0 or 1, with 1 signifying that unwritten
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extent flagging should occur.
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If the suboption is omitted, unwritten extent flagging is enabled.
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If unwritten extents are flagged, filesystem write performance
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will be negatively affected for preallocated file extents, since
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extra filesystem transactions are required to convert extent flags
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for the range of the file written.
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This suboption should be disabled if the filesystem
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needs to be used on operating system versions which do not support the
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This option specifies the inode size of the filesystem, and other
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inode allocation parameters.
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The XFS inode contains a fixed-size part and a variable-size part.
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The variable-size part, whose size is affected by this option, can contain:
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directory data, for small directories;
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attribute data, for small attribute sets;
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symbolic link data, for small symbolic links;
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the extent list for the file, for files with a small number of extents;
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and the root of a tree describing the location of extents for the file,
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for files with a large number of extents.
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The valid suboptions for specifying inode size are:
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\f3log=\f1\f2value\f1,
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\f3perblock=\f1\f2value\f1,
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\f3size=\f1\f2value\f1;
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only one can be supplied.
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The inode size is specified either as a base two logarithm value with
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or as the number fitting in a filesystem block with
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The mininum (and default) value is 256 bytes.
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The maximum value is 2048 (2 KB) subject to the restriction that
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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
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significant bits in an inode number
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is affected by filesystem geometry. In
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practice, filesystem size and inode size are the predominant factors.
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The Linux kernel and most applications cannot currently handle
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inode numbers greater than 32 significant bits, so if no
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inode size is given on the command line,
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will attempt to choose a size
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such that inode numbers will be < 32 bits. If an inode size
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is specified, or if a filesystem is sufficently large,
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will warn if this will create inode numbers > 32 significant
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The option \f3maxpct=\f1\f2value\f1 specifies the maximum percentage
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of space in the filesystem that can be allocated to inodes.
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The default value is 25%.
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Setting the value to 0 means that
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essentially all of the filesystem can become inode blocks.
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is used to specify that inode allocation is or is not aligned.
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The value is either 0 or 1,
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with 1 signifying that inodes are allocated aligned.
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If the value is omitted, 1 is assumed.
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The default is that inodes are aligned.
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Aligned inode access is normally more efficient than unaligned access;
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alignment must be established at the time the filesystem is created,
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since inodes are allocated at that time.
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This option can be used to turn off inode alignment when the
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filesystem needs to be mountable by a version of IRIX
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that does not have the inode alignment feature
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(any release of IRIX before 6.2, and IRIX 6.2 without XFS patches).
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These options specify the location, size, and other parameters of the
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log section of the filesystem.
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The valid suboptions are:
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.BI internal[= value ]
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\f3size=\f1\f2value\f1.
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suboption is used to specify that the log section is a piece of
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the data section instead of being another device or logical volume.
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The suboption value is either 0 or 1,
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with 1 signifying that the log is internal.
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If the value is omitted, 1 is assumed.
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suboption is used to specify the size of the log section.
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If the log is contained within the data section and
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will try to select a suitable log size depending
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on the size of the filesystem. The actual logsize depends on the
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filesystem block size and the directory block size.
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option is only needed if the log section of the filesystem
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should occupy less space than the size of the special file.
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The size is specified in bytes or blocks, with a \f3b\f1 suffix
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meaning multiplication by the filesystem block size, as described above.
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The overriding minimum value for size is 512 blocks.
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With some combinations of filesystem block size, inode size,
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and directory block size, the minimum log size is larger than 512 blocks.
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These options specify the version and size parameters for the naming
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(directory) area of the filesystem.
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The valid suboptions are:
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\f3log=\f1\f2value\f1,
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\f3size=\f1\f2value\f1,
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\f3version=\f1\f2value\f1.
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The naming (directory) version is 1 or 2,
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defaulting to 2 if unspecified.
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With version 2 directories,
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the directory block size can be any power of 2 size
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from the filesystem block size up to 65536.
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The block size is specified either as a base two logarithm value with
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The default size value for version 2 directories is 4096 bytes (4 KB),
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unless the filesystem block size is larger than 4096,
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in which case the default value is the filesystem block size.
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For version 1 directories the block size is the same as the
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filesystem block size.
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\f3\-p\f1 \f2protofile\f1
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and takes its directions from that file.
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The blocks and inodes
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are provided for backwards compatibility, but are otherwise unused.
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contains tokens separated by spaces or
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A sample prototype specification follows (line numbers have been added to
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aid in the explanation):
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\f71 /stand/\f1\f2diskboot\f1\f7
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5 sh ---755 3 1 /bin/sh
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11 slink l--644 3 1 /a/symbolic/link
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12 : This is a comment line
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Line 1 is a dummy string.
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(It was formerly the bootfilename.)
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It is present for backward
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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
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the proto file to cause it to be parsed correctly; the value
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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).
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These are also merely for backward compatibility: two numeric values must
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appear at this point for the proto file to be correctly parsed,
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but their values are immaterial since they are ignored.
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about files and directories to
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be included in this filesystem.
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Line 3 specifies the root directory.
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Lines 4-6 and 8-10 specifies other directories and files.
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Note the special symbolic link syntax on line 11.
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to end the branch of the filesystem it is on, and continue
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from the next higher directory.
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It must be the last character
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on line 12 introduces a comment; all characters up until the
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following newline are ignored.
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Note that this means you cannot
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have a file in a prototype file whose name contains a colon.
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on lines 13 and 14 end the process, since no additional
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specifications follow.
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File specifications give the mode,
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and the initial contents of the file.
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Valid syntax for the contents field
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depends on the first character of the mode.
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The mode for a file is specified by a 6-character string.
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specifies the type of the file.
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The character range is
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to specify regular, block special,
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character special, directory files, named pipes (fifos), and symbolic
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The second character of the mode
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to specify setuserID mode or not.
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for the setgroupID mode.
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is a three digit octal number giving the
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owner, group, and other read, write, execute
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tokens come after the mode; they specify the
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user and group IDs of the owner of the file.
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If the file is a regular file,
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the next token of the specification can be a pathname
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from which the contents and size are copied.
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If the file is a block or character special file,
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follow that give the major and minor device numbers.
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If the file is a symbolic link, the next token of the specification
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is used as the contents of the link.
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If the file is a directory,
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reads a list of names and
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file specifications for the entries
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As noted above, the scan is terminated with the
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prints the parameters of the filesystem
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flag suppresses this.
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Real-time section options.
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These options specify the location, size, and other parameters of the
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real-time section of the filesystem.
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The valid suboptions are:
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\f3size=\f1\f2value\f1.
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suboption is used to specify the size of the blocks in the real-time
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section of the filesystem.
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This size must be a multiple of the filesystem block size.
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The minimum allowed value is the filesystem block size
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or 4 KB (whichever is larger);
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the default value is the stripe width for striped volumes or 64 KB for
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the maximum allowed value is 1 GB.
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The real-time extent size should be carefully chosen to match the
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parameters of the physical media used.
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suboption is used to specify the size of the real-time section.
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This suboption is only needed if the real-time section of the
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filesystem should occupy
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less space than the size of the partition or logical volume containing the section.
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Disable overlapping partition/volume checks.
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By default \f2mkfs.xfs\f1 checks to see if the destination partition or logical
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volume overlaps any mounted or reserved partitions in the system. If an
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overlap or mount conflict is found, the user will be notified and prevented
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from potentially corrupting the existing data. For systems with
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a large number of disks, this additional checking may add noticable overhead
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to the command's execution time. For situations where command performance is
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necessary, this switch may be used to disable the safeguards. Due to the
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potential for user-error causing corrupted filesystems or other on-disk
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data corruption, we strongly discourage use of this switch in normal operation.
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\f3\-L\f1 \f2label\f1
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Set the filesystem label.
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XFS filesystem labels can be at most 12 characters long; if
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is longer than 12 characters,
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will not proceed with creating the filesystem. Refer to the
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manual entries for additional information.
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With a prototype file, it is not possible to specify hard links.
added
removed
man/man8/mkfs.xfs.8
