{ "mode": "man", "parameter": "MKE2FS", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/MKE2FS/8/json", "generated": "2026-06-10T16:22:28Z", "synopsis": "mke2fs [ -c | -l filename ] [ -b block-size ] [ -C cluster-size ] [ -d root-directory ] [ -D\n] [ -g blocks-per-group ] [ -G number-of-groups ] [ -i bytes-per-inode ] [ -I inode-size ] [", "sections": { "NAME": { "content": "mke2fs - create an ext2/ext3/ext4 file system\n", "subsections": [] }, "SYNOPSIS": { "content": "mke2fs [ -c | -l filename ] [ -b block-size ] [ -C cluster-size ] [ -d root-directory ] [ -D\n] [ -g blocks-per-group ] [ -G number-of-groups ] [ -i bytes-per-inode ] [ -I inode-size ] [", "subsections": [ { "name": "-j -J -N -n -m", "content": "[ -o creator-os ] [ -O [^]feature[,...] ] [ -q ] [ -r fs-revision-level ] [ -E extended-op‐\ntions ] [ -v ] [ -F ] [ -L volume-label ] [ -M last-mounted-directory ] [ -S ] [ -t fs-type ]\n[ -T usage-type ] [ -U UUID ] [ -V ] [ -e errors-behavior ] [ -z undofile ] device [ fs-size\n]\n\nmke2fs -O journaldev [ -b block-size ] [ -L volume-label ] [ -n ] [ -q ] [ -v ] external-\njournal [ fs-size ]\n", "flag": "-m" } ] }, "DESCRIPTION": { "content": "mke2fs is used to create an ext2, ext3, or ext4 file system, usually in a disk partition (or\nfile) named by device.\n\nThe file system size is specified by fs-size. If fs-size does not have a suffix, it is in‐\nterpreted as power-of-two kilobytes, unless the -b blocksize option is specified, in which\ncase fs-size is interpreted as the number of blocksize blocks. If the fs-size is suffixed\nby 'k', 'm', 'g', 't' (either upper-case or lower-case), then it is interpreted in power-of-\ntwo kilobytes, megabytes, gigabytes, terabytes, etc. If fs-size is omitted, mke2fs will cre‐\nate the file system based on the device size.\n\nIf mke2fs is run as mkfs.XXX (i.e., mkfs.ext2, mkfs.ext3, or mkfs.ext4) the option -t XXX is\nimplied; so mkfs.ext3 will create a file system for use with ext3, mkfs.ext4 will create a\nfile system for use with ext4, and so on.\n\nThe defaults of the parameters for the newly created file system, if not overridden by the\noptions listed below, are controlled by the /etc/mke2fs.conf configuration file. See the\nmke2fs.conf(5) manual page for more details.\n", "subsections": [] }, "OPTIONS": { "content": "", "subsections": [ { "name": "-b", "content": "Specify the size of blocks in bytes. Valid block-size values are powers of two from\n1024 up to 65536 (however note that the kernel is able to mount only file systems with\nblock-size smaller or equal to the system page size - 4k on x86 systems, up to 64k on\nppc64 or aarch64 depending on kernel configuration). If omitted, block-size is\nheuristically determined by the file system size and the expected usage of the file\nsystem (see the -T option). In most common cases, the default block size is 4k. If\nblock-size is preceded by a negative sign ('-'), then mke2fs will use heuristics to\ndetermine the appropriate block size, with the constraint that the block size will be\nat least block-size bytes. This is useful for certain hardware devices which require\nthat the blocksize be a multiple of 2k.\n", "flag": "-b" }, { "name": "-c", "content": "specified twice, then a slower read-write test is used instead of a fast read-only\ntest.\n", "flag": "-c" }, { "name": "-C cluster-size", "content": "Specify the size of cluster in bytes for file systems using the bigalloc feature.\nValid cluster-size values are from 2048 to 256M bytes per cluster. This can only be\nspecified if the bigalloc feature is enabled. (See the ext4 (5) man page for more de‐\ntails about bigalloc.) The default cluster size if bigalloc is enabled is 16 times\nthe block size.\n", "flag": "-C" }, { "name": "-d", "content": "Copy the contents of the given directory into the root directory of the file system.\n", "flag": "-d" }, { "name": "-D", "content": "cache memory, which may impact other applications running on a busy server. This op‐\ntion will cause mke2fs to run much more slowly, however, so there is a tradeoff to us‐\ning direct I/O.\n", "flag": "-D" }, { "name": "-e", "content": "Change the behavior of the kernel code when errors are detected. In all cases, a file\nsystem error will cause e2fsck(8) to check the file system on the next boot. error-\nbehavior can be one of the following:\n\ncontinue Continue normal execution.\n\nremount-ro Remount file system read-only.\n\npanic Cause a kernel panic.\n", "flag": "-e" }, { "name": "-E", "content": "Set extended options for the file system. Extended options are comma separated, and\nmay take an argument using the equals ('=') sign. The -E option used to be -R in ear‐\nlier versions of mke2fs. The -R option is still accepted for backwards compatibility,\nbut is deprecated. The following extended options are supported:\n\nencoding=encoding-name\nEnable the casefold feature in the super block and set encoding-name as\nthe encoding to be used. If encoding-name is not specified, the encoding\ndefined in mke2fs.conf(5) is used.\n\nencodingflags=encoding-flags\nDefine parameters for file name character encoding operations. If a flag\nis not changed using this parameter, its default value is used. encoding-\nflags should be a comma-separated lists of flags to be enabled. To dis‐\nable a flag, add it to the list with the prefix \"no\".\n\nThe only flag that can be set right now is strict which means that invalid\nstrings should be rejected by the file system. In the default configura‐\ntion, the strict flag is disabled.\n\nmmpupdateinterval=interval\nAdjust the initial MMP update interval to interval seconds. Specifying an\ninterval of 0 means to use the default interval. The specified interval\nmust be less than 300 seconds. Requires that the mmp feature be enabled.\n\nstride=stride-size\nConfigure the file system for a RAID array with stride-size file system\nblocks. This is the number of blocks read or written to disk before moving\nto the next disk, which is sometimes referred to as the chunk size. This\nmostly affects placement of file system metadata like bitmaps at mke2fs\ntime to avoid placing them on a single disk, which can hurt performance.\nIt may also be used by the block allocator.\n\nstripewidth=stripe-width\nConfigure the file system for a RAID array with stripe-width file system\nblocks per stripe. This is typically stride-size * N, where N is the num‐\nber of data-bearing disks in the RAID (e.g. for RAID 5 there is one parity\ndisk, so N will be the number of disks in the array minus 1). This allows\nthe block allocator to prevent read-modify-write of the parity in a RAID\nstripe if possible when the data is written.\n\noffset=offset\nCreate the file system at an offset from the beginning of the device or\nfile. This can be useful when creating disk images for virtual machines.\n\nresize=max-online-resize\nReserve enough space so that the block group descriptor table can grow to\nsupport a file system that has max-online-resize blocks.\n\nlazyitableinit[= <0 to disable, 1 to enable>]\nIf enabled and the uninitbg feature is enabled, the inode table will not\nbe fully initialized by mke2fs. This speeds up file system initialization\nnoticeably, but it requires the kernel to finish initializing the file\nsystem in the background when the file system is first mounted. If the\noption value is omitted, it defaults to 1 to enable lazy inode table zero‐\ning.\n\nlazyjournalinit[= <0 to disable, 1 to enable>]\nIf enabled, the journal inode will not be fully zeroed out by mke2fs.\nThis speeds up file system initialization noticeably, but carries some\nsmall risk if the system crashes before the journal has been overwritten\nentirely one time. If the option value is omitted, it defaults to 1 to\nenable lazy journal inode zeroing.\n\nnocopyxattrs\nNormally mke2fs will copy the extended attributes of the files in the di‐\nrectory hierarchy specified via the (optional) -d option. This will dis‐\nable the copy and leaves the files in the newly created file system with‐\nout any extended attributes.\n\nnumbackupsb=<0|1|2>\nIf the sparsesuper2 file system feature is enabled this option controls\nwhether there will be 0, 1, or 2 backup superblocks created in the file\nsystem.\n\npackedmetablocks[= <0 to disable, 1 to enable>]\nPlace the allocation bitmaps and the inode table at the beginning of the\ndisk. This option requires that the flexbg file system feature to be en‐\nabled in order for it to have effect, and will also create the journal at\nthe beginning of the file system. This option is useful for flash devices\nthat use SLC flash at the beginning of the disk. It also maximizes the\nrange of contiguous data blocks, which can be useful for certain special‐\nized use cases, such as supported Shingled Drives.\n\nrootowner[=uid:gid]\nSpecify the numeric user and group ID of the root directory. If no\nUID:GID is specified, use the user and group ID of the user running\nmke2fs. In mke2fs 1.42 and earlier the UID and GID of the root directory\nwere set by default to the UID and GID of the user running the mke2fs com‐\nmand. The rootowner= option allows explicitly specifying these values,\nand avoid side-effects for users that do not expect the contents of the\nfile system to change based on the user running mke2fs.\n\ntestfs\nSet a flag in the file system superblock indicating that it may be mounted\nusing experimental kernel code, such as the ext4dev file system.\n\ndiscard\nAttempt to discard blocks at mkfs time (discarding blocks initially is\nuseful on solid state devices and sparse / thin-provisioned storage). When\nthe device advertises that discard also zeroes data (any subsequent read\nafter the discard and before write returns zero), then mark all not-yet-\nzeroed inode tables as zeroed. This significantly speeds up file system\ninitialization. This is set as default.\n\nnodiscard\nDo not attempt to discard blocks at mkfs time.\n\nquotatype\nSpecify the which quota types (usrquota, grpquota, prjquota) which should\nbe enabled in the created file system. The argument of this extended op‐\ntion should be a colon separated list. This option has effect only if the\nquota feature is set. The default quota types to be initialized if this\noption is not specified is both user and group quotas. If the project\nfeature is enabled that project quotas will be initialized as well.\n", "flag": "-E" }, { "name": "-F", "content": "on a block special device, or if other parameters do not make sense. In order to\nforce mke2fs to create a file system even if the file system appears to be in use or\nis mounted (a truly dangerous thing to do), this option must be specified twice.\n", "flag": "-F" }, { "name": "-g", "content": "Specify the number of blocks in a block group. There is generally no reason for the\nuser to ever set this parameter, as the default is optimal for the file system. (For\nadministrators who are creating file systems on RAID arrays, it is preferable to use\nthe stride RAID parameter as part of the -E option rather than manipulating the number\nof blocks per group.) This option is generally used by developers who are developing\ntest cases.\n\nIf the bigalloc feature is enabled, the -g option will specify the number of clusters\nin a block group.\n", "flag": "-g" }, { "name": "-G", "content": "Specify the number of block groups that will be packed together to create a larger\nvirtual block group (or \"flexbg group\") in an ext4 file system. This improves meta-\ndata locality and performance on meta-data heavy workloads. The number of groups must\nbe a power of 2 and may only be specified if the flexbg file system feature is en‐\nabled.\n", "flag": "-G" }, { "name": "-i", "content": "Specify the bytes/inode ratio. mke2fs creates an inode for every bytes-per-inode\nbytes of space on the disk. The larger the bytes-per-inode ratio, the fewer inodes\nwill be created. This value generally shouldn't be smaller than the blocksize of the\nfile system, since in that case more inodes would be made than can ever be used. Be\nwarned that it is not possible to change this ratio on a file system after it is cre‐\nated, so be careful deciding the correct value for this parameter. Note that resizing\na file system changes the number of inodes to maintain this ratio.\n", "flag": "-i" }, { "name": "-I", "content": "Specify the size of each inode in bytes. The inode-size value must be a power of 2\nlarger or equal to 128. The larger the inode-size the more space the inode table will\nconsume, and this reduces the usable space in the file system and can also negatively\nimpact performance. It is not possible to change this value after the file system is\ncreated.\n\nFile systems with an inode size of 128 bytes do not support timestamps beyond January\n19, 2038. Inodes which are 256 bytes or larger will support extended timestamps,\nproject id's, and the ability to store some extended attributes in the inode table for\nimproved performance.\n\nThe default inode size is controlled by the mke2fs.conf(5) file. In the mke2fs.conf\nfile shipped with e2fsprogs, the default inode size is 256 bytes for most file sys‐\ntems, except for small file systems where the inode size will be 128 bytes.\n", "flag": "-I" }, { "name": "-j -J", "content": "default journal parameters will be used to create an appropriately sized journal\n(given the size of the file system) stored within the file system. Note that you must\nbe using a kernel which has ext3 support in order to actually make use of the journal.\n", "flag": "-J" }, { "name": "-J", "content": "Create the ext3 journal using options specified on the command-line. Journal options\nare comma separated, and may take an argument using the equals ('=') sign. The fol‐\nlowing journal options are supported:\n\nsize=journal-size\nCreate an internal journal (i.e., stored inside the file system) of size\njournal-size megabytes. The size of the journal must be at least 1024\nfile system blocks (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks,\netc.) and may be no more than 10,240,000 file system blocks or half the\ntotal file system size (whichever is smaller)\n\nfastcommitsize=fast-commit-size\nCreate an additional fast commit journal area of size fast-commit-size\nkilobytes. This option is only valid if fastcommit feature is enabled on\nthe file system. If this option is not specified and if fastcommit fea‐\nture is turned on, fast commit area size defaults to journal-size / 64\nmegabytes. The total size of the journal with fastcommit feature set is\njournal-size + ( fast-commit-size * 1024) megabytes. The total journal\nsize may be no more than 10,240,000 file system blocks or half the total\nfile system size (whichever is smaller).\n\nlocation=journal-location\nSpecify the location of the journal. The argument journal-location can\neither be specified as a block number, or if the number has a units suffix\n(e.g., 'M', 'G', etc.) interpret it as the offset from the beginning of\nthe file system.\n\ndevice=external-journal\nAttach the file system to the journal block device located on external-\njournal. The external journal must already have been created using the\ncommand\n\nmke2fs -O journaldev external-journal\n\nNote that external-journal must have been created with the same block size\nas the new file system. In addition, while there is support for attaching\nmultiple file systems to a single external journal, the Linux kernel and\ne2fsck(8) do not currently support shared external journals yet.\n\nInstead of specifying a device name directly, external-journal can also be\nspecified by either LABEL=label or UUID=UUID to locate the external jour‐\nnal by either the volume label or UUID stored in the ext2 superblock at\nthe start of the journal. Use dumpe2fs(8) to display a journal device's\nvolume label and UUID. See also the -L option of tune2fs(8).\n\nOnly one of the size or device options can be given for a file system.\n", "flag": "-J" }, { "name": "-l", "content": "Read the bad blocks list from filename. Note that the block numbers in the bad block\nlist must be generated using the same block size as used by mke2fs. As a result, the\n-c option to mke2fs is a much simpler and less error-prone method of checking a disk\nfor bad blocks before formatting it, as mke2fs will automatically pass the correct pa‐\nrameters to the badblocks program.\n", "flag": "-l" }, { "name": "-L", "content": "Set the volume label for the file system to new-volume-label. The maximum length of\nthe volume label is 16 bytes.\n", "flag": "-L" }, { "name": "-m", "content": "Specify the percentage of the file system blocks reserved for the super-user. This\navoids fragmentation, and allows root-owned daemons, such as syslogd(8), to continue\nto function correctly after non-privileged processes are prevented from writing to the\nfile system. The default percentage is 5%.\n", "flag": "-m" }, { "name": "-M", "content": "Set the last mounted directory for the file system. This might be useful for the sake\nof utilities that key off of the last mounted directory to determine where the file\nsystem should be mounted.\n", "flag": "-M" }, { "name": "-n", "content": "were to create a file system. This can be used to determine the location of the\nbackup superblocks for a particular file system, so long as the mke2fs parameters that\nwere passed when the file system was originally created are used again. (With the -n\noption added, of course!)\n", "flag": "-n" }, { "name": "-N", "content": "Overrides the default calculation of the number of inodes that should be reserved for\nthe file system (which is based on the number of blocks and the bytes-per-inode ra‐\ntio). This allows the user to specify the number of desired inodes directly.\n", "flag": "-N" }, { "name": "-o", "content": "Overrides the default value of the \"creator operating system\" field of the file sys‐\ntem. The creator field is set by default to the name of the OS the mke2fs executable\nwas compiled for.\n", "flag": "-o" }, { "name": "-O", "content": "Create a file system with the given features (file system options), overriding the de‐\nfault file system options. The features that are enabled by default are specified by\nthe basefeatures relation, either in the [defaults] section in the /etc/mke2fs.conf\nconfiguration file, or in the [fstypes] subsections for the usage types as specified\nby the -T option, further modified by the features relation found in the [fstypes]\nsubsections for the file system and usage types. See the mke2fs.conf(5) manual page\nfor more details. The file system type-specific configuration setting found in the\n[fstypes] section will override the global default found in [defaults].\n\nThe file system feature set will be further edited using either the feature set speci‐\nfied by this option, or if this option is not given, by the defaultfeatures relation\nfor the file system type being created, or in the [defaults] section of the configura‐\ntion file.\n\nThe file system feature set is comprised of a list of features, separated by commas,\nthat are to be enabled. To disable a feature, simply prefix the feature name with a\ncaret ('^') character. Features with dependencies will not be removed successfully.\nThe pseudo-file system feature \"none\" will clear all file system features.\n\nFor more information about the features which can be set, please see\nthe manual page ext4(5).\n", "flag": "-O" }, { "name": "-q", "content": "", "flag": "-q" }, { "name": "-r", "content": "Set the file system revision for the new file system. Note that 1.2 kernels only sup‐\nport revision 0 file systems. The default is to create revision 1 file systems.\n", "flag": "-r" }, { "name": "-S", "content": "only in the very unlikely case that all of the superblock and backup superblocks are\ncorrupted, and a last-ditch recovery method is desired by experienced users. It\ncauses mke2fs to reinitialize the superblock and group descriptors, while not touching\nthe inode table and the block and inode bitmaps. The e2fsck program should be run im‐\nmediately after this option is used, and there is no guarantee that any data will be\nsalvageable. Due to the wide variety of possible options to mke2fs that affect the\non-disk layout, it is critical to specify exactly the same format options, such as\nblocksize, fs-type, feature flags, and other tunables when using this option, or the\nfile system will be further corrupted. In some cases, such as file systems that have\nbeen resized, or have had features enabled after format time, it is impossible to\noverwrite all of the superblocks correctly, and at least some file system corruption\nwill occur. It is best to run this on a full copy of the file system so other options\ncan be tried if this doesn't work.\n", "flag": "-S" }, { "name": "-t", "content": "Specify the file system type (i.e., ext2, ext3, ext4, etc.) that is to be created. If\nthis option is not specified, mke2fs will pick a default either via how the command\nwas run (for example, using a name of the form mkfs.ext2, mkfs.ext3, etc.) or via a\ndefault as defined by the /etc/mke2fs.conf file. This option controls which file\nsystem options are used by default, based on the fstypes configuration stanza in\n/etc/mke2fs.conf.\n\nIf the -O option is used to explicitly add or remove file system options that should\nbe set in the newly created file system, the resulting file system may not be sup‐\nported by the requested fs-type. (e.g., \"mke2fs -t ext3 -O extent /dev/sdXX\" will\ncreate a file system that is not supported by the ext3 implementation as found in the\nLinux kernel; and \"mke2fs -t ext3 -O ^hasjournal /dev/hdXX\" will create a file system\nthat does not have a journal and hence will not be supported by the ext3 file system\ncode in the Linux kernel.)\n", "flag": "-t" }, { "name": "-T", "content": "Specify how the file system is going to be used, so that mke2fs can choose optimal\nfile system parameters for that use. The usage types that are supported are defined\nin the configuration file /etc/mke2fs.conf. The user may specify one or more usage\ntypes using a comma separated list.\n\nIf this option is is not specified, mke2fs will pick a single default usage type based\non the size of the file system to be created. If the file system size is less than 3\nmegabytes, mke2fs will use the file system type floppy. If the file system size is\ngreater than or equal to 3 but less than 512 megabytes, mke2fs(8) will use the file\nsystem type small. If the file system size is greater than or equal to 4 terabytes\nbut less than 16 terabytes, mke2fs(8) will use the file system type big. If the file\nsystem size is greater than or equal to 16 terabytes, mke2fs(8) will use the file sys‐\ntem type huge. Otherwise, mke2fs(8) will use the default file system type default.\n", "flag": "-T" }, { "name": "-U", "content": "Set the universally unique identifier (UUID) of the file system to UUID. The format\nof the UUID is a series of hex digits separated by hyphens, like this:\n\"c1b9d5a2-f162-11cf-9ece-0020afc76f16\". The UUID parameter may also be one of the\nfollowing:\n\nclear clear the file system UUID\n\nrandom generate a new randomly-generated UUID\n\ntime generate a new time-based UUID\n", "flag": "-U" }, { "name": "-v", "content": "", "flag": "-v" }, { "name": "-V", "content": "", "flag": "-V" }, { "name": "-z", "content": "Before overwriting a file system block, write the old contents of the block to an undo\nfile. This undo file can be used with e2undo(8) to restore the old contents of the\nfile system should something go wrong. If the empty string is passed as the undofile\nargument, the undo file will be written to a file named mke2fs-device.e2undo in the\ndirectory specified via the E2FSPROGSUNDODIR environment variable or the undodir\ndirective in the configuration file.\n\nWARNING: The undo file cannot be used to recover from a power or system crash.\n", "flag": "-z" } ] }, "ENVIRONMENT": { "content": "MKE2FSSYNC\nIf set to non-zero integer value, its value is used to determine how often sync(2) is\ncalled during inode table initialization.\n\nMKE2FSCONFIG\nDetermines the location of the configuration file (see mke2fs.conf(5)).\n\nMKE2FSFIRSTMETABG\nIf set to non-zero integer value, its value is used to determine first meta block\ngroup. This is mostly for debugging purposes.\n\nMKE2FSDEVICESECTSIZE\nIf set to non-zero integer value, its value is used to determine logical sector size\nof the device.\n\nMKE2FSDEVICEPHYSSECTSIZE\nIf set to non-zero integer value, its value is used to determine physical sector size\nof the device.\n\nMKE2FSSKIPCHECKMSG\nIf set, do not show the message of file system automatic check caused by mount count\nor check interval.\n", "subsections": [] }, "AUTHOR": { "content": "This version of mke2fs has been written by Theodore Ts'o .\n", "subsections": [] }, "AVAILABILITY": { "content": "mke2fs is part of the e2fsprogs package and is available from http://e2fsprogs.source‐\nforge.net.\n", "subsections": [] }, "SEE ALSO": { "content": "mke2fs.conf(5), badblocks(8), dumpe2fs(8), e2fsck(8), tune2fs(8), ext4(5)\n\n\n\nE2fsprogs version 1.46.5 December 2021 MKE2FS(8)", "subsections": [] } }, "summary": "mke2fs - create an ext2/ext3/ext4 file system", "flags": [ { "flag": "-b", "long": null, "arg": null, "description": "Specify the size of blocks in bytes. Valid block-size values are powers of two from 1024 up to 65536 (however note that the kernel is able to mount only file systems with block-size smaller or equal to the system page size - 4k on x86 systems, up to 64k on ppc64 or aarch64 depending on kernel configuration). If omitted, block-size is heuristically determined by the file system size and the expected usage of the file system (see the -T option). In most common cases, the default block size is 4k. If block-size is preceded by a negative sign ('-'), then mke2fs will use heuristics to determine the appropriate block size, with the constraint that the block size will be at least block-size bytes. This is useful for certain hardware devices which require that the blocksize be a multiple of 2k." }, { "flag": "-c", "long": null, "arg": null, "description": "specified twice, then a slower read-write test is used instead of a fast read-only test." }, { "flag": "-C", "long": null, "arg": null, "description": "Specify the size of cluster in bytes for file systems using the bigalloc feature. Valid cluster-size values are from 2048 to 256M bytes per cluster. This can only be specified if the bigalloc feature is enabled. (See the ext4 (5) man page for more de‐ tails about bigalloc.) The default cluster size if bigalloc is enabled is 16 times the block size." }, { "flag": "-d", "long": null, "arg": null, "description": "Copy the contents of the given directory into the root directory of the file system." }, { "flag": "-D", "long": null, "arg": null, "description": "cache memory, which may impact other applications running on a busy server. This op‐ tion will cause mke2fs to run much more slowly, however, so there is a tradeoff to us‐ ing direct I/O." }, { "flag": "-e", "long": null, "arg": null, "description": "Change the behavior of the kernel code when errors are detected. In all cases, a file system error will cause e2fsck(8) to check the file system on the next boot. error- behavior can be one of the following: continue Continue normal execution. remount-ro Remount file system read-only. panic Cause a kernel panic." }, { "flag": "-E", "long": null, "arg": null, "description": "Set extended options for the file system. Extended options are comma separated, and may take an argument using the equals ('=') sign. The -E option used to be -R in ear‐ lier versions of mke2fs. The -R option is still accepted for backwards compatibility, but is deprecated. The following extended options are supported: encoding=encoding-name Enable the casefold feature in the super block and set encoding-name as the encoding to be used. If encoding-name is not specified, the encoding defined in mke2fs.conf(5) is used. encodingflags=encoding-flags Define parameters for file name character encoding operations. If a flag is not changed using this parameter, its default value is used. encoding- flags should be a comma-separated lists of flags to be enabled. To dis‐ able a flag, add it to the list with the prefix \"no\". The only flag that can be set right now is strict which means that invalid strings should be rejected by the file system. In the default configura‐ tion, the strict flag is disabled. mmpupdateinterval=interval Adjust the initial MMP update interval to interval seconds. Specifying an interval of 0 means to use the default interval. The specified interval must be less than 300 seconds. Requires that the mmp feature be enabled. stride=stride-size Configure the file system for a RAID array with stride-size file system blocks. This is the number of blocks read or written to disk before moving to the next disk, which is sometimes referred to as the chunk size. This mostly affects placement of file system metadata like bitmaps at mke2fs time to avoid placing them on a single disk, which can hurt performance. It may also be used by the block allocator. stripewidth=stripe-width Configure the file system for a RAID array with stripe-width file system blocks per stripe. This is typically stride-size * N, where N is the num‐ ber of data-bearing disks in the RAID (e.g. for RAID 5 there is one parity disk, so N will be the number of disks in the array minus 1). This allows the block allocator to prevent read-modify-write of the parity in a RAID stripe if possible when the data is written. offset=offset Create the file system at an offset from the beginning of the device or file. This can be useful when creating disk images for virtual machines. resize=max-online-resize Reserve enough space so that the block group descriptor table can grow to support a file system that has max-online-resize blocks. lazyitableinit[= <0 to disable, 1 to enable>] If enabled and the uninitbg feature is enabled, the inode table will not be fully initialized by mke2fs. This speeds up file system initialization noticeably, but it requires the kernel to finish initializing the file system in the background when the file system is first mounted. If the option value is omitted, it defaults to 1 to enable lazy inode table zero‐ ing. lazyjournalinit[= <0 to disable, 1 to enable>] If enabled, the journal inode will not be fully zeroed out by mke2fs. This speeds up file system initialization noticeably, but carries some small risk if the system crashes before the journal has been overwritten entirely one time. If the option value is omitted, it defaults to 1 to enable lazy journal inode zeroing. nocopyxattrs Normally mke2fs will copy the extended attributes of the files in the di‐ rectory hierarchy specified via the (optional) -d option. This will dis‐ able the copy and leaves the files in the newly created file system with‐ out any extended attributes. numbackupsb=<0|1|2> If the sparsesuper2 file system feature is enabled this option controls whether there will be 0, 1, or 2 backup superblocks created in the file system. packedmetablocks[= <0 to disable, 1 to enable>] Place the allocation bitmaps and the inode table at the beginning of the disk. This option requires that the flexbg file system feature to be en‐ abled in order for it to have effect, and will also create the journal at the beginning of the file system. This option is useful for flash devices that use SLC flash at the beginning of the disk. It also maximizes the range of contiguous data blocks, which can be useful for certain special‐ ized use cases, such as supported Shingled Drives. rootowner[=uid:gid] Specify the numeric user and group ID of the root directory. If no UID:GID is specified, use the user and group ID of the user running mke2fs. In mke2fs 1.42 and earlier the UID and GID of the root directory were set by default to the UID and GID of the user running the mke2fs com‐ mand. The rootowner= option allows explicitly specifying these values, and avoid side-effects for users that do not expect the contents of the file system to change based on the user running mke2fs. testfs Set a flag in the file system superblock indicating that it may be mounted using experimental kernel code, such as the ext4dev file system. discard Attempt to discard blocks at mkfs time (discarding blocks initially is useful on solid state devices and sparse / thin-provisioned storage). When the device advertises that discard also zeroes data (any subsequent read after the discard and before write returns zero), then mark all not-yet- zeroed inode tables as zeroed. This significantly speeds up file system initialization. This is set as default. nodiscard Do not attempt to discard blocks at mkfs time. quotatype Specify the which quota types (usrquota, grpquota, prjquota) which should be enabled in the created file system. The argument of this extended op‐ tion should be a colon separated list. This option has effect only if the quota feature is set. The default quota types to be initialized if this option is not specified is both user and group quotas. If the project feature is enabled that project quotas will be initialized as well." }, { "flag": "-F", "long": null, "arg": null, "description": "on a block special device, or if other parameters do not make sense. In order to force mke2fs to create a file system even if the file system appears to be in use or is mounted (a truly dangerous thing to do), this option must be specified twice." }, { "flag": "-g", "long": null, "arg": null, "description": "Specify the number of blocks in a block group. There is generally no reason for the user to ever set this parameter, as the default is optimal for the file system. (For administrators who are creating file systems on RAID arrays, it is preferable to use the stride RAID parameter as part of the -E option rather than manipulating the number of blocks per group.) This option is generally used by developers who are developing test cases. If the bigalloc feature is enabled, the -g option will specify the number of clusters in a block group." }, { "flag": "-G", "long": null, "arg": null, "description": "Specify the number of block groups that will be packed together to create a larger virtual block group (or \"flexbg group\") in an ext4 file system. This improves meta- data locality and performance on meta-data heavy workloads. The number of groups must be a power of 2 and may only be specified if the flexbg file system feature is en‐ abled." }, { "flag": "-i", "long": null, "arg": null, "description": "Specify the bytes/inode ratio. mke2fs creates an inode for every bytes-per-inode bytes of space on the disk. The larger the bytes-per-inode ratio, the fewer inodes will be created. This value generally shouldn't be smaller than the blocksize of the file system, since in that case more inodes would be made than can ever be used. Be warned that it is not possible to change this ratio on a file system after it is cre‐ ated, so be careful deciding the correct value for this parameter. Note that resizing a file system changes the number of inodes to maintain this ratio." }, { "flag": "-I", "long": null, "arg": null, "description": "Specify the size of each inode in bytes. The inode-size value must be a power of 2 larger or equal to 128. The larger the inode-size the more space the inode table will consume, and this reduces the usable space in the file system and can also negatively impact performance. It is not possible to change this value after the file system is created. File systems with an inode size of 128 bytes do not support timestamps beyond January 19, 2038. Inodes which are 256 bytes or larger will support extended timestamps, project id's, and the ability to store some extended attributes in the inode table for improved performance. The default inode size is controlled by the mke2fs.conf(5) file. In the mke2fs.conf file shipped with e2fsprogs, the default inode size is 256 bytes for most file sys‐ tems, except for small file systems where the inode size will be 128 bytes." }, { "flag": "-J", "long": null, "arg": null, "description": "default journal parameters will be used to create an appropriately sized journal (given the size of the file system) stored within the file system. Note that you must be using a kernel which has ext3 support in order to actually make use of the journal." }, { "flag": "-J", "long": null, "arg": null, "description": "Create the ext3 journal using options specified on the command-line. Journal options are comma separated, and may take an argument using the equals ('=') sign. The fol‐ lowing journal options are supported: size=journal-size Create an internal journal (i.e., stored inside the file system) of size journal-size megabytes. The size of the journal must be at least 1024 file system blocks (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.) and may be no more than 10,240,000 file system blocks or half the total file system size (whichever is smaller) fastcommitsize=fast-commit-size Create an additional fast commit journal area of size fast-commit-size kilobytes. This option is only valid if fastcommit feature is enabled on the file system. If this option is not specified and if fastcommit fea‐ ture is turned on, fast commit area size defaults to journal-size / 64 megabytes. The total size of the journal with fastcommit feature set is journal-size + ( fast-commit-size * 1024) megabytes. The total journal size may be no more than 10,240,000 file system blocks or half the total file system size (whichever is smaller). location=journal-location Specify the location of the journal. The argument journal-location can either be specified as a block number, or if the number has a units suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the beginning of the file system. device=external-journal Attach the file system to the journal block device located on external- journal. The external journal must already have been created using the command mke2fs -O journaldev external-journal Note that external-journal must have been created with the same block size as the new file system. In addition, while there is support for attaching multiple file systems to a single external journal, the Linux kernel and e2fsck(8) do not currently support shared external journals yet. Instead of specifying a device name directly, external-journal can also be specified by either LABEL=label or UUID=UUID to locate the external jour‐ nal by either the volume label or UUID stored in the ext2 superblock at the start of the journal. Use dumpe2fs(8) to display a journal device's volume label and UUID. See also the -L option of tune2fs(8). Only one of the size or device options can be given for a file system." }, { "flag": "-l", "long": null, "arg": null, "description": "Read the bad blocks list from filename. Note that the block numbers in the bad block list must be generated using the same block size as used by mke2fs. As a result, the -c option to mke2fs is a much simpler and less error-prone method of checking a disk for bad blocks before formatting it, as mke2fs will automatically pass the correct pa‐ rameters to the badblocks program." }, { "flag": "-L", "long": null, "arg": null, "description": "Set the volume label for the file system to new-volume-label. The maximum length of the volume label is 16 bytes." }, { "flag": "-m", "long": null, "arg": null, "description": "Specify the percentage of the file system blocks reserved for the super-user. This avoids fragmentation, and allows root-owned daemons, such as syslogd(8), to continue to function correctly after non-privileged processes are prevented from writing to the file system. The default percentage is 5%." }, { "flag": "-M", "long": null, "arg": null, "description": "Set the last mounted directory for the file system. This might be useful for the sake of utilities that key off of the last mounted directory to determine where the file system should be mounted." }, { "flag": "-n", "long": null, "arg": null, "description": "were to create a file system. This can be used to determine the location of the backup superblocks for a particular file system, so long as the mke2fs parameters that were passed when the file system was originally created are used again. (With the -n option added, of course!)" }, { "flag": "-N", "long": null, "arg": null, "description": "Overrides the default calculation of the number of inodes that should be reserved for the file system (which is based on the number of blocks and the bytes-per-inode ra‐ tio). This allows the user to specify the number of desired inodes directly." }, { "flag": "-o", "long": null, "arg": null, "description": "Overrides the default value of the \"creator operating system\" field of the file sys‐ tem. The creator field is set by default to the name of the OS the mke2fs executable was compiled for." }, { "flag": "-O", "long": null, "arg": null, "description": "Create a file system with the given features (file system options), overriding the de‐ fault file system options. The features that are enabled by default are specified by the basefeatures relation, either in the [defaults] section in the /etc/mke2fs.conf configuration file, or in the [fstypes] subsections for the usage types as specified by the -T option, further modified by the features relation found in the [fstypes] subsections for the file system and usage types. See the mke2fs.conf(5) manual page for more details. The file system type-specific configuration setting found in the [fstypes] section will override the global default found in [defaults]. The file system feature set will be further edited using either the feature set speci‐ fied by this option, or if this option is not given, by the defaultfeatures relation for the file system type being created, or in the [defaults] section of the configura‐ tion file. The file system feature set is comprised of a list of features, separated by commas, that are to be enabled. To disable a feature, simply prefix the feature name with a caret ('^') character. Features with dependencies will not be removed successfully. The pseudo-file system feature \"none\" will clear all file system features. For more information about the features which can be set, please see the manual page ext4(5)." }, { "flag": "-q", "long": null, "arg": null, "description": "" }, { "flag": "-r", "long": null, "arg": null, "description": "Set the file system revision for the new file system. Note that 1.2 kernels only sup‐ port revision 0 file systems. The default is to create revision 1 file systems." }, { "flag": "-S", "long": null, "arg": null, "description": "only in the very unlikely case that all of the superblock and backup superblocks are corrupted, and a last-ditch recovery method is desired by experienced users. It causes mke2fs to reinitialize the superblock and group descriptors, while not touching the inode table and the block and inode bitmaps. The e2fsck program should be run im‐ mediately after this option is used, and there is no guarantee that any data will be salvageable. Due to the wide variety of possible options to mke2fs that affect the on-disk layout, it is critical to specify exactly the same format options, such as blocksize, fs-type, feature flags, and other tunables when using this option, or the file system will be further corrupted. In some cases, such as file systems that have been resized, or have had features enabled after format time, it is impossible to overwrite all of the superblocks correctly, and at least some file system corruption will occur. It is best to run this on a full copy of the file system so other options can be tried if this doesn't work." }, { "flag": "-t", "long": null, "arg": null, "description": "Specify the file system type (i.e., ext2, ext3, ext4, etc.) that is to be created. If this option is not specified, mke2fs will pick a default either via how the command was run (for example, using a name of the form mkfs.ext2, mkfs.ext3, etc.) or via a default as defined by the /etc/mke2fs.conf file. This option controls which file system options are used by default, based on the fstypes configuration stanza in /etc/mke2fs.conf. If the -O option is used to explicitly add or remove file system options that should be set in the newly created file system, the resulting file system may not be sup‐ ported by the requested fs-type. (e.g., \"mke2fs -t ext3 -O extent /dev/sdXX\" will create a file system that is not supported by the ext3 implementation as found in the Linux kernel; and \"mke2fs -t ext3 -O ^hasjournal /dev/hdXX\" will create a file system that does not have a journal and hence will not be supported by the ext3 file system code in the Linux kernel.)" }, { "flag": "-T", "long": null, "arg": null, "description": "Specify how the file system is going to be used, so that mke2fs can choose optimal file system parameters for that use. The usage types that are supported are defined in the configuration file /etc/mke2fs.conf. The user may specify one or more usage types using a comma separated list. If this option is is not specified, mke2fs will pick a single default usage type based on the size of the file system to be created. If the file system size is less than 3 megabytes, mke2fs will use the file system type floppy. If the file system size is greater than or equal to 3 but less than 512 megabytes, mke2fs(8) will use the file system type small. If the file system size is greater than or equal to 4 terabytes but less than 16 terabytes, mke2fs(8) will use the file system type big. If the file system size is greater than or equal to 16 terabytes, mke2fs(8) will use the file sys‐ tem type huge. Otherwise, mke2fs(8) will use the default file system type default." }, { "flag": "-U", "long": null, "arg": null, "description": "Set the universally unique identifier (UUID) of the file system to UUID. The format of the UUID is a series of hex digits separated by hyphens, like this: \"c1b9d5a2-f162-11cf-9ece-0020afc76f16\". The UUID parameter may also be one of the following: clear clear the file system UUID random generate a new randomly-generated UUID time generate a new time-based UUID" }, { "flag": "-v", "long": null, "arg": null, "description": "" }, { "flag": "-V", "long": null, "arg": null, "description": "" }, { "flag": "-z", "long": null, "arg": null, "description": "Before overwriting a file system block, write the old contents of the block to an undo file. This undo file can be used with e2undo(8) to restore the old contents of the file system should something go wrong. If the empty string is passed as the undofile argument, the undo file will be written to a file named mke2fs-device.e2undo in the directory specified via the E2FSPROGSUNDODIR environment variable or the undodir directive in the configuration file. WARNING: The undo file cannot be used to recover from a power or system crash." } ], "examples": [], "see_also": [ { "name": "mke2fs.conf", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/mke2fs.conf/5/json" }, { "name": "badblocks", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/badblocks/8/json" }, { "name": "dumpe2fs", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/dumpe2fs/8/json" }, { "name": "e2fsck", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/e2fsck/8/json" }, { "name": "tune2fs", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/tune2fs/8/json" }, { "name": "ext4", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/ext4/5/json" } ] }