mkfs.xfs - construct an XFS filesystem
mkfs.xfs [ -b subopt=value ] [ -d subopt[=value] ] [ -i subopt=value ]
|
[ -l subopt[=value] ] [ -n subopt[=value] ] [ -p protofile ] [ -q ] |
|
[ -r subopt[=value] ] [ -C ] device |
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 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 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 commaseparated 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 bytes, blocks, kilobytes, or megabytes. Sizes are treated as hexadecimal if prefixed by 0x or 0X, octal if prefixed by 0, or decimal otherwise. If suffixed with b then the size is converted by multiplying it by the filesystem's block size. If suffixed 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 If suffixed with g then the size is converted by multiplying it by 1073741824 (1024 * 1024 * 1024).
|
-b |
Block size options. This option specifies the fundamental block size of the filesystem. 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 KB). The minimum value for block size is 512; the maximum is 65536 (64 KB). XFS on Linux currently only supports 4KB 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, file[=value], name=value, size=value, sunit=value, swidth=value, and unwritten[=value]. The agcount suboption 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 MB; the maximum size is just under 4 GB. The data section of the filesystem is divided into agcount allocation groups (default value 8, unless the filesystem is smaller than 128 MB or larger than 8 GB). 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 name suboption 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 realtime section. Note that the default log in this case is an internal log with at least 1000 blocks, actual size depending on the filesystem block size and the directory block size. |
|
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 suboption is used only to make a filesystem image (for instance, a miniroot image). If the value is omitted then 1 is assumed. The size suboption 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. 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 512byte block units. 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 512KB. Also inode allocations and the internal log will be stripe unit aligned. 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 512byte block units. This suboption is required if -d sunit has been specified and it has to be a multiple of the -d sunit suboption. The stripe width will be the preferred iosize returned in the stat(2) system call. 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, filesystem write performance will be negatively affected for preallocated file extents, since extra filesystem transactions are required to convert extent flags for the range of the file written. This suboption should be disabled if the filesystem needs to be used on operating system versions which do not support the flagging capability. |
|
-i |
Inode options. This option specifies the inode size of the filesystem, and other inode allocation parameters. The XFS inode contains a fixedsize part and a variablesize part. The variablesize 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 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 KB) subject to the restriction that the inode size cannot exceed one half of the filesystem block size. 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 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). |
||
|
-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] and size=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 size suboption is used to specify the size of the log section. This suboption is required if -l internal[=1] is given. Otherwise, it 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. |
|
|
-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 1 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 KB), 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. |
|
|
-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 prototype file contains tokens separated by spaces or newlines. A sample prototype specification follows (line numbers have been added to aid in the explanation): 1 /stand/diskboot 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. Lines 311 tell mkfs.xfs about files and directories to be included in this filesystem. Line 3 specifies the root directory. Lines 46 and 810 specifies other directories and files. Note the special symbolic link syntax on line 11. The $ on line 7 tells mkfs.xfs to end the branch of the filesystem it is on, and continue from the next higher directory. 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 give the mode, the user ID, the group ID, and the initial contents of the file. Valid syntax for the contents field depends on the first character of the mode. The mode for a file is specified by a 6character string. The first character specifies the type of the file. The character range is -bcdpl to specify regular, block special, character special, directory files, named pipes (fifos), and symbolic links, respectively. The second character of the mode is either u or - to specify setuserID mode or not. The third is g or - for the setgroupID mode. The rest of the mode is a three digit octal number giving the owner, group, and other read, write, execute permissions (see chmod(1)). Two decimal number tokens come after the mode; they specify the user and group IDs of the owner of the file. If the file is a regular file, the next token of the specification can be a pathname from which the contents and size are copied. If the file is a block or character special file, two decimal numbers follow that give the major and minor device numbers. If the file is a symbolic link, the next token of the specification is used as the contents of the link. If the file is a directory, mkfs.xfs makes the entries . and .. and then reads a list of names and (recursively) file specifications for the entries in the directory. As noted above, the scan is terminated with the token $. |
|
-q |
|
-r |
Normally mkfs.xfs prints the parameters Realtime section options. |
of |
the |
filesystem |
to |
be |
These options specify the location, size, and other parameters of the
realtime section of the filesystem. The valid suboptions are:
extsize=value and size=value.
|
The extsize suboption is used to specify the size of the blocks in the realtime 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 KB (whichever is larger); the default value is the stripe width for striped volumes or 64 KB for nonstriped volumes; the maximum allowed value is 1 GB. The realtime 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 realtime section. This suboption is only needed if the realtime section of the filesystem should occupy less space than the size of the partition or logical volume containing the section. |
|
-C |
|
By default mkfs.xfs checks to see if the destination partition or logical volume overlaps any mounted or reserved partitions in the system. If an |
|
overlap or mount conflict is found, the user will be notified and prevented from potentially corrupting the existing data. For systems |
with a large number of disks, this additional checking may add noticable
overhead to the command's execution time. For situations where
command performance is necessary, this switch may be used to disable
the safeguards. Due to the potential for usererror causing corrupted
filesystems or other ondisk data corruption, we strongly discourage use
of this switch in normal operation.
mkfs(8).
With a prototype file, it is not possible to specify hard links.