{ "content": [ { "type": "text", "text": "# MKFS.FAT (info)\n\n## NAME\n\nmkfs.fat - create an MS-DOS FAT filesystem\n\n## SYNOPSIS\n\nmkfs.fat [OPTIONS] DEVICE [BLOCK-COUNT]\n\n## DESCRIPTION\n\nmkfs.fat is used to create a FAT filesystem on a device or in an image\nfile. DEVICE is the special file corresponding to the device (e.g.\n/dev/sdXX) or the image file (which does not need to exist when the op-\ntion -C is given). BLOCK-COUNT is the number of blocks on the device\nand size of one block is always 1024 bytes, independently of the sector\nsize or the cluster size. Therefore BLOCK-COUNT specifies size of\nfilesystem in KiB unit and not in the number of sectors (like for all\nother mkfs.fat options). If omitted, mkfs.fat automatically chooses a\nfilesystem size to fill the available space.\n\n## Sections\n\n- **NAME**\n- **SYNOPSIS**\n- **DESCRIPTION**\n- **OPTIONS** (3 subsections)\n- **BUGS**\n- **SEE ALSO**\n- **HOMEPAGE**\n- **AUTHORS**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n" } ], "structuredContent": { "command": "MKFS.FAT", "section": "", "mode": "info", "summary": "mkfs.fat - create an MS-DOS FAT filesystem", "synopsis": "mkfs.fat [OPTIONS] DEVICE [BLOCK-COUNT]", "tldr_summary": null, "tldr_examples": [], "tldr_source": null, "flags": [ { "flag": "", "long": null, "arg": null, "description": "Fill (fake) MBR table with disk signature one partition which starts at sector 0 (includes MBR itself) and spans whole disk de- vice. It is needed only for non-removable disks used on Microsoft Windows systems and only when formatting whole unpartitioned disk. Location of the disk signature and partition table overlaps with the end of the first FAT sector (boot code location), therefore there is no additional space usage. Default is auto mode in which mkfs.fat put MBR table only for non-removable disks when formatting whole unpartitioned disk. -n VOLUME-NAME Sets the volume name (label) of the filesystem. The volume name can be up to 11 characters long. Supplying an empty string, a string consisting only of white space or the string \"NO NAME\" as VOLUME-NAME has the same effect as not giving the -n option. The default is no label. --codepage=PAGE Use DOS codepage PAGE to encode label. By default codepage 850 is used. -r ROOT-DIR-ENTRIES Select the minimal number of entries available in the root direc- tory. The default is 112 or 224 for floppies and 512 for hard disks. Note that this is minimal number and it may be increased by mkfs.fat due to alignment of structures. See also mkfs.fat option -a. -R NUMBER-OF-RESERVED-SECTORS Select the minimal number of reserved sectors. With FAT32 format at least 2 reserved sectors are needed, the default is 32. Other- wise the default is 1 (only the boot sector). Note that this is minimal number and it may be increased by mkfs.fat due to alignment of structures. See also mkfs.fat option -a. -s SECTORS-PER-CLUSTER Specify the number of disk sectors per cluster. Must be a power of 2, i.e. 1, 2, 4, 8, ... 128. -S LOGICAL-SECTOR-SIZE Specify the number of bytes per logical sector. Must be a power of 2 and greater than or equal to 512, i.e. 512, 1024, 2048, 4096, 8192, 16384, or 32768. Values larger than 4096 are not conforming to the FAT file system specification and may not work everywhere. -v Verbose execution. --offset SECTOR Write the filesystem at a specific sector into the device file. This is useful for creating a filesystem in a partitioned disk im- age without having to set up a loop device. --variant TYPE Create a filesystem of variant TYPE. Acceptable values are stan- dard and atari (in any combination of upper/lower case). See above under DESCRIPTION for the differences." }, { "flag": "", "long": "--help", "arg": null, "description": "Display option summary and exit." }, { "flag": "", "long": "--invariant", "arg": null, "description": "Use constants for normally randomly generated or time based data such as volume ID and creation time. Multiple runs of mkfs.fat on the same device create identical results with this option. Its main purpose is testing mkfs.fat." } ], "examples": [], "see_also": [ { "name": "fatlabel", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/fatlabel/8/json" }, { "name": "fsck.fat", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/fsck.fat/8/json" } ], "section_outline": [ { "name": "NAME", "lines": 2, "subsections": [] }, { "name": "SYNOPSIS", "lines": 2, "subsections": [] }, { "name": "DESCRIPTION", "lines": 26, "subsections": [] }, { "name": "OPTIONS", "lines": 106, "subsections": [ { "name": "--mbr[=y|yes|n|no|a|auto]", "lines": 57 }, { "name": "--help", "lines": 2, "long": "--help" }, { "name": "--invariant", "lines": 5, "long": "--invariant" } ] }, { "name": "BUGS", "lines": 4, "subsections": [] }, { "name": "SEE ALSO", "lines": 2, "subsections": [] }, { "name": "HOMEPAGE", "lines": 3, "subsections": [] }, { "name": "AUTHORS", "lines": 6, "subsections": [] } ], "sections": { "NAME": { "content": "mkfs.fat - create an MS-DOS FAT filesystem\n", "subsections": [] }, "SYNOPSIS": { "content": "mkfs.fat [OPTIONS] DEVICE [BLOCK-COUNT]\n", "subsections": [] }, "DESCRIPTION": { "content": "mkfs.fat is used to create a FAT filesystem on a device or in an image\nfile. DEVICE is the special file corresponding to the device (e.g.\n/dev/sdXX) or the image file (which does not need to exist when the op-\ntion -C is given). BLOCK-COUNT is the number of blocks on the device\nand size of one block is always 1024 bytes, independently of the sector\nsize or the cluster size. Therefore BLOCK-COUNT specifies size of\nfilesystem in KiB unit and not in the number of sectors (like for all\nother mkfs.fat options). If omitted, mkfs.fat automatically chooses a\nfilesystem size to fill the available space.\n\nTwo different variants of the FAT filesystem are supported. Standard\nis the FAT12, FAT16 and FAT32 filesystems as defined by Microsoft and\nwidely used on hard disks and removable media like USB sticks and SD\ncards. The other is the legacy Atari variant used on Atari ST.\n\nIn Atari mode, if not directed otherwise by the user, mkfs.fat will al-\nways use 2 sectors per cluster, since GEMDOS doesn't like other values\nvery much. It will also obey the maximum number of sectors GEMDOS can\nhandle. Larger filesystems are managed by raising the logical sector\nsize. An Atari-compatible serial number for the filesystem is gener-\nated, and a 12 bit FAT is used only for filesystems that have one of\nthe usual floppy sizes (720k, 1.2M, 1.44M, 2.88M), a 16 bit FAT other-\nwise. This can be overridden with the -F option. Some PC-specific\nboot sector fields aren't written, and a boot message (option -m) is\nignored.\n", "subsections": [] }, "OPTIONS": { "content": "-a Normally, for any filesystem except very small ones, mkfs.fat will\nalign all the data structures to cluster size, to make sure that as\nlong as the partition is properly aligned, so will all the data\nstructures in the filesystem. This option disables alignment; this\nmay provide a handful of additional clusters of storage at the ex-\npense of a significant performance degradation on RAIDs, flash me-\ndia or large-sector hard disks.\n\n-A Select using the Atari variation of the FAT filesystem if that\nisn't active already, otherwise select standard FAT filesystem.\nThis is selected by default if mkfs.fat is run on 68k Atari Linux.\n\n-b SECTOR-OF-BACKUP\nSelects the location of the backup boot sector for FAT32. Default\ndepends on number of reserved sectors, but usually is sector 6. If\nthere is a free space available after the backup boot sector then\nbackup of the FAT32 info sector is put after the backup boot sec-\ntor, usually at sector 7. The backup must be within the range of\nreserved sectors. Value 0 completely disables creating of backup\nboot and info FAT32 sectors.\n\n-c Check the device for bad blocks before creating the filesystem.\n\n-C Create the file given as DEVICE on the command line, and write the\nto-be-created filesystem to it. This can be used to create the new\nfilesystem in a file instead of on a real device, and to avoid us-\ning dd in advance to create a file of appropriate size. With this\noption, the BLOCK-COUNT must be given, because otherwise the in-\ntended size of the filesystem wouldn't be known. The file created\nis a sparse file, which actually only contains the meta-data areas\n(boot sector, FATs, and root directory). The data portions won't\nbe stored on the disk, but the file nevertheless will have the cor-\nrect size. The resulting file can be copied later to a floppy disk\nor other device, or mounted through a loop device.\n\n-D DRIVE-NUMBER\nSpecify the BIOS drive number to be stored in the FAT boot sector.\nFor hard disks and removable medias it is usually 0x80-0xFF (0x80\nis first hard disk C:, 0x81 is second hard disk D:, ...), for\nfloppy devices or partitions to be used for floppy emulation it is\n0x00-0x7F (0x00 is first floppy A:, 0x01 is second floppy B:).\n\n-f NUMBER-OF-FATS\nSpecify the number of file allocation tables in the filesystem.\nThe default is 2.\n\n-F FAT-SIZE\nSpecifies the type of file allocation tables used (12, 16 or 32\nbit). If nothing is specified, mkfs.fat will automatically select\nbetween 12, 16 and 32 bit, whatever fits better for the filesystem\nsize.\n\n-g HEADS/SECTORS-PER-TRACK\nSpecify HEADS and SECTORS-PER-TRACK numbers which represents disk\ngeometry of DEVICE. Both numbers are stored into the FAT boot sec-\ntor. Number SECTORS-PER-TRACK is used also for aligning the total\ncount of FAT sectors. By default disk geometry is read from DEVICE\nitself. If it is not available then LBA-Assist Translation and\ntranslation table from the SD Card Part 2 File System Specification\nbased on total number of disk sectors is used.\n\n-h NUMBER-OF-HIDDEN-SECTORS\nSpecify the number of so-called hidden sectors, as stored in the\nFAT boot sector: this number represents the beginning sector of the\npartition containing the file system. Normally this is an offset\n(in sectors) relative to the start of the disk, although for MBR\nlogical volumes contained in an extended partition of type 0x05 (a\nnon-LBA extended partition), a quirk in the MS-DOS implementation\nof FAT requires it to be relative to the partition's immediate con-\ntaining Extended Boot Record. Boot code and other software han-\ndling FAT volumes may also rely on this field being set up cor-\nrectly; most modern FAT implementations will ignore it. By de-\nfault, if the DEVICE is a partition block device, mkfs.fat uses the\npartition offset relative to disk start. Otherwise, mkfs.fat as-\nsumes zero. Use this option to override this behaviour.\n\n-i VOLUME-ID\nSets the volume ID of the newly created filesystem; VOLUME-ID is a\n32-bit hexadecimal number (for example, 2e24ec82). The default is\na number which depends on the filesystem creation time.\n\n-I Ignore and disable safety checks. By default mkfs.fat refuses to\ncreate a filesystem on a device with partitions or virtual mapping.\nmkfs.fat will complain and tell you that it refuses to work. This\nis different when using MO disks. One doesn't always need parti-\ntions on MO disks. The filesystem can go directly to the whole\ndisk. Under other OSes this is known as the superfloppy format.\nThis switch will force mkfs.fat to work properly.\n\n-l FILENAME\nRead the bad blocks list from FILENAME.\n\n-m MESSAGE-FILE\nSets the message the user receives on attempts to boot this\nfilesystem without having properly installed an operating system.\nThe message file must not exceed 418 bytes once line feeds have\nbeen converted to carriage return-line feed combinations, and tabs\nhave been expanded. If the filename is a hyphen (-), the text is\ntaken from standard input.\n\n-M FAT-MEDIA-TYPE\nSpecify the media type to be stored in the FAT boot sector. This\nvalue is usually 0xF8 for hard disks and is 0xF0 or a value from\n0xF9 to 0xFF for floppies or partitions to be used for floppy emu-\nlation.\n", "subsections": [ { "name": "--mbr[=y|yes|n|no|a|auto]", "content": "Fill (fake) MBR table with disk signature one partition which\nstarts at sector 0 (includes MBR itself) and spans whole disk de-\nvice. It is needed only for non-removable disks used on Microsoft\nWindows systems and only when formatting whole unpartitioned disk.\nLocation of the disk signature and partition table overlaps with\nthe end of the first FAT sector (boot code location), therefore\nthere is no additional space usage. Default is auto mode in which\nmkfs.fat put MBR table only for non-removable disks when formatting\nwhole unpartitioned disk.\n\n-n VOLUME-NAME\nSets the volume name (label) of the filesystem. The volume name\ncan be up to 11 characters long. Supplying an empty string, a\nstring consisting only of white space or the string \"NO NAME\" as\nVOLUME-NAME has the same effect as not giving the -n option. The\ndefault is no label.\n\n--codepage=PAGE\nUse DOS codepage PAGE to encode label. By default codepage 850 is\nused.\n\n-r ROOT-DIR-ENTRIES\nSelect the minimal number of entries available in the root direc-\ntory. The default is 112 or 224 for floppies and 512 for hard\ndisks. Note that this is minimal number and it may be increased by\nmkfs.fat due to alignment of structures. See also mkfs.fat option\n-a.\n\n-R NUMBER-OF-RESERVED-SECTORS\nSelect the minimal number of reserved sectors. With FAT32 format\nat least 2 reserved sectors are needed, the default is 32. Other-\nwise the default is 1 (only the boot sector). Note that this is\nminimal number and it may be increased by mkfs.fat due to alignment\nof structures. See also mkfs.fat option -a.\n\n-s SECTORS-PER-CLUSTER\nSpecify the number of disk sectors per cluster. Must be a power of\n2, i.e. 1, 2, 4, 8, ... 128.\n\n-S LOGICAL-SECTOR-SIZE\nSpecify the number of bytes per logical sector. Must be a power of\n2 and greater than or equal to 512, i.e. 512, 1024, 2048, 4096,\n8192, 16384, or 32768. Values larger than 4096 are not conforming\nto the FAT file system specification and may not work everywhere.\n\n-v Verbose execution.\n\n--offset SECTOR\nWrite the filesystem at a specific sector into the device file.\nThis is useful for creating a filesystem in a partitioned disk im-\nage without having to set up a loop device.\n\n--variant TYPE\nCreate a filesystem of variant TYPE. Acceptable values are stan-\ndard and atari (in any combination of upper/lower case). See above\nunder DESCRIPTION for the differences.\n" }, { "name": "--help", "content": "Display option summary and exit.\n", "long": "--help" }, { "name": "--invariant", "content": "Use constants for normally randomly generated or time based data\nsuch as volume ID and creation time. Multiple runs of mkfs.fat on\nthe same device create identical results with this option. Its\nmain purpose is testing mkfs.fat.\n", "long": "--invariant" } ] }, "BUGS": { "content": "mkfs.fat can not create boot-able filesystems. This isn't as easy as\nyou might think at first glance for various reasons and has been dis-\ncussed a lot already. mkfs.fat simply will not support it ;)\n", "subsections": [] }, "SEE ALSO": { "content": "fatlabel(8), fsck.fat(8)\n", "subsections": [] }, "HOMEPAGE": { "content": "The home for the dosfstools project is its GitHub project page\n.\n", "subsections": [] }, "AUTHORS": { "content": "dosfstools were written by Werner Almesberger , Roman Hodek ,\nand others. Current maintainers are Andreas Bombe and\nPali Rohar .\n\ndosfstools 4.2 2021-01-31 MKFS.FAT(8)", "subsections": [] } } } }