From 464df1d5e5ab1322e2dd0a7796939fff1aeefa9a Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 17:49:25 +0200 Subject: Adding upstream version 1.47.0. Signed-off-by: Daniel Baumann --- misc/mke2fs.8.in | 891 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 891 insertions(+) create mode 100644 misc/mke2fs.8.in (limited to 'misc/mke2fs.8.in') diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in new file mode 100644 index 0000000..30f97bb --- /dev/null +++ b/misc/mke2fs.8.in @@ -0,0 +1,891 @@ +.\" -*- nroff -*- +.\" Copyright 1993, 1994, 1995 by Theodore Ts'o. All Rights Reserved. +.\" This file may be copied under the terms of the GNU Public License. +.\" +.TH MKE2FS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@" +.SH NAME +mke2fs \- create an ext2/ext3/ext4 file system +.SH SYNOPSIS +.B mke2fs +[ +.B \-c +| +.B \-l +.I filename +] +[ +.B \-b +.I block-size +] +[ +.B \-C +.I cluster-size +] +[ +.B \-d +.I root-directory +] +[ +.B \-D +] +[ +.B \-g +.I blocks-per-group +] +[ +.B \-G +.I number-of-groups +] +[ +.B \-i +.I bytes-per-inode +] +[ +.B \-I +.I inode-size +] +[ +.B \-j +] +[ +.B \-J +.I journal-options +] +[ +.B \-N +.I number-of-inodes +] +[ +.B \-n +] +[ +.B \-m +.I reserved-blocks-percentage +] +[ +.B \-o +.I creator-os +] +[ +.B \-O +[^]\fIfeature\fR[,...] +] +[ +.B \-q +] +[ +.B \-r +.I fs-revision-level +] +[ +.B \-E +.I extended-options +] +[ +.B \-v +] +[ +.B \-F +] +[ +.B \-L +.I volume-label +] +[ +.B \-M +.I last-mounted-directory +] +[ +.B \-S +] +[ +.B \-t +.I fs-type +] +[ +.B \-T +.I usage-type +] +[ +.B \-U +.I UUID +] +[ +.B \-V +] +[ +.B \-e +.I errors-behavior +] +[ +.B \-z +.I undo_file +] +.I device +[ +.I fs-size +] +@JDEV@.sp +@JDEV@.B "mke2fs \-O journal_dev" +@JDEV@[ +@JDEV@.B \-b +@JDEV@.I block-size +@JDEV@] +.\" No external-journal specific journal options yet (size is ignored) +.\" @JDEV@[ +.\" @JDEV@.B \-J +.\" @JDEV@.I journal-options +.\" @JDEV@] +@JDEV@[ +@JDEV@.B \-L +@JDEV@.I volume-label +@JDEV@] +@JDEV@[ +@JDEV@.B \-n +@JDEV@] +@JDEV@[ +@JDEV@.B \-q +@JDEV@] +@JDEV@[ +@JDEV@.B \-v +@JDEV@] +@JDEV@.I external-journal +@JDEV@[ +@JDEV@.I fs-size +@JDEV@] +.SH DESCRIPTION +.B mke2fs +is used to create an ext2, ext3, or ext4 file system, usually in a disk +partition (or file) named by +.IR device . +.PP +The file system size is specified by +.IR fs-size . +If +.I fs-size +does not have a suffix, it is interpreted as power-of-two kilobytes, +unless the +.B \-b +.I blocksize +option is specified, in which case +.I fs-size +is interpreted as the number of +.I blocksize +blocks. If the fs-size is suffixed by 'k', 'm', 'g', 't' +(either upper-case or lower-case), then it is interpreted in +power-of-two kilobytes, megabytes, gigabytes, terabytes, etc. +If +.I fs-size +is omitted, +.B mke2fs +will create the file system based on the device size. +.PP +If +.B mke2fs +is run as +.B mkfs.XXX +(i.e., +.BR mkfs.ext2 , +.BR mkfs.ext3 , +or +.BR mkfs.ext4 ) +the option +.B \-t +.I XXX +is implied; so +.B mkfs.ext3 +will create a file system for use with ext3, +.B mkfs.ext4 +will create a file system for use with ext4, and so on. +.PP +The defaults of the parameters for the newly created file system, if not +overridden by the options listed below, are controlled by the +.B /etc/mke2fs.conf +configuration file. See the +.BR mke2fs.conf (5) +manual page for more details. +.SH OPTIONS +.TP +.BI \-b " block-size" +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 +.B \-T +option). In most common cases, the default block size is 4k. If +.I block-size +is preceded by a negative sign ('-'), then +.B mke2fs +will use heuristics to determine the +appropriate block size, with the constraint that the block size will be +at least +.I block-size +bytes. This is useful for certain hardware devices which require that +the blocksize be a multiple of 2k. +.TP +.B \-c +Check the device for bad blocks before creating the file system. If +this option is specified twice, then a slower read-write +test is used instead of a fast read-only test. +.TP +.B \-C " cluster-size" +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 +.B ext4 (5) +man page for more details about bigalloc.) The default cluster size if +bigalloc is enabled is 16 times the block size. +.TP +.BI \-d " root-directory" +Copy the contents of the given directory into the root directory of the +file system. +.TP +.B \-D +Use direct I/O when writing to the disk. This avoids mke2fs dirtying a +lot of buffer cache memory, which may impact other applications running +on a busy server. This option will cause mke2fs to run much more +slowly, however, so there is a tradeoff to using direct I/O. +.TP +.BI \-e " error-behavior" +Change the behavior of the kernel code when errors are detected. +In all cases, a file system error will cause +.BR e2fsck (8) +to check the file system on the next boot. +.I error-behavior +can be one of the following: +.RS 1.2i +.TP 1.2i +.B continue +Continue normal execution. +.TP +.B remount-ro +Remount file system read-only. +.TP +.B panic +Cause a kernel panic. +.RE +.TP +.BI \-E " extended-options" +Set extended options for the file system. Extended options are comma +separated, and may take an argument using the equals ('=') sign. The +.B \-E +option used to be +.B \-R +in earlier versions of +.BR mke2fs . +The +.B \-R +option is still accepted for backwards compatibility, but is deprecated. +The following extended options are supported: +.RS 1.2i +.TP +.BI encoding= encoding-name +Enable the +.I casefold +feature in the super block and set +.I encoding-name +as the encoding to be used. If +.I encoding-name +is not specified, the encoding defined in +.BR mke2fs.conf (5) +is used. +.TP +.BI encoding_flags= encoding-flags +Define parameters for file name character encoding operations. If a +flag is not changed using this parameter, its default value is used. +.I encoding-flags +should be a comma-separated lists of flags to be enabled. To disable a +flag, add it to the list with the prefix "no". + +The only flag that can be set right now is +.I strict +which means that invalid strings should be rejected by the file system. +In the default configuration, the +.I strict +flag is disabled. +.TP +.BI mmp_update_interval= interval +Adjust the initial MMP update interval to +.I interval +seconds. Specifying an +.I interval +of 0 means to use the default interval. The specified interval must +be less than 300 seconds. Requires that the +.B mmp +feature be enabled. +.TP +.BI stride= stride-size +Configure the file system for a RAID array with +.I 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 +.I chunk size. +This mostly affects placement of file system metadata like bitmaps at +.B mke2fs +time to avoid placing them on a single disk, which can hurt performance. +It may also be used by the block allocator. +.TP +.BI stripe_width= stripe-width +Configure the file system for a RAID array with +.I stripe-width +file system blocks per stripe. This is typically stride-size * N, where +N is the number 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. +.TP +.BI 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. +.TP +.BI resize= max-online-resize +Reserve enough space so that the block group descriptor table can grow +to support a file system that has +.I max-online-resize +blocks. +.TP +.B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR] +If enabled and the uninit_bg feature is enabled, the inode table will +not be fully initialized by +.BR 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 zeroing. +.TP +.B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR] +If enabled, the journal inode will not be fully zeroed out by +.BR 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. +.TP +.B assume_storage_prezeroed\fR[\fB= \fI<0 to disable, 1 to enable>\fR] +If enabled, +.BR mke2fs +assumes that the storage device has been prezeroed, skips zeroing the journal +and inode tables, and annotates the block group flags to signal that the inode +table has been zeroed. +.TP +.B no_copy_xattrs +Normally +.B mke2fs +will copy the extended attributes of the files in the directory +hierarchy specified via the (optional) +.B \-d +option. This will disable the copy and leaves the files in the newly +created file system without any extended attributes. +.TP +.BI num_backup_sb= <0|1|2> +If the +.B sparse_super2 +file system feature is enabled this option controls whether there will +be 0, 1, or 2 backup superblocks created in the file system. +.TP +.B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR] +Place the allocation bitmaps and the inode table at the beginning of the +disk. This option requires that the flex_bg file system feature to be +enabled 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 specialized use cases, such as supported +Shingled Drives. +.TP +.BI root_owner [=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 \fBmke2fs\fR. +In \fBmke2fs\fR 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 command. +The \fBroot_owner=\fR 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 \fBmke2fs\fR. +.TP +.B test_fs +Set a flag in the file system superblock indicating that it may be +mounted using experimental kernel code, such as the ext4dev file system. +.TP +.BI orphan_file_size= size +Set size of the file for tracking unlinked but still open inodes and inodes +with truncate in progress. Larger file allows for better scalability, reserving +a few blocks per cpu is ideal. +.TP +.B 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. +.TP +.B nodiscard +Do not attempt to discard blocks at mkfs time. +.TP +.B quotatype +Specify the which quota types (usrquota, grpquota, prjquota) which +should be enabled in the created file system. The argument of this +extended option should be a colon separated list. This option has +effect only if the +.B 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. +.RE +.TP +.B \-F +Force +.B mke2fs +to create a file system, even if the specified device is not a partition +on a block special device, or if other parameters do not make sense. +In order to force +.B 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. +.TP +.BI \-g " blocks-per-group" +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 +.I stride +RAID parameter as part of the +.B \-E +option rather than manipulating the number of blocks per group.) +This option is generally used by developers who +are developing test cases. +.IP +If the bigalloc feature is enabled, the +.B \-g +option will specify the number of clusters in a block group. +.TP +.BI \-G " number-of-groups" +Specify the number of block groups that will be packed together to +create a larger virtual block group (or "flex_bg 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 +.B flex_bg +file system feature is enabled. +.TP +.BI \-i " bytes-per-inode" +Specify the bytes/inode ratio. +.B mke2fs +creates an inode for every +.I bytes-per-inode +bytes of space on the disk. The larger the +.I 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 created, 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. +.TP +.BI \-I " inode-size" +Specify the size of each inode in bytes. +The +.I inode-size +value must be a power of 2 larger or equal to 128. The larger the +.I 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. +.IP +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. +.IP +The default inode size is controlled by the +.BR mke2fs.conf (5) +file. In the +.B mke2fs.conf +file shipped with e2fsprogs, the default inode size is 256 bytes for +most file systems, except for small file systems where the inode size +will be 128 bytes. +.TP +.B \-j +Create the file system with an ext3 journal. If the +.B \-J +option is not specified, the 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. +.TP +.BI \-J " journal-options" +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 following journal options are supported: +.RS 1.2i +.TP +.BI size= journal-size +Create an internal journal (i.e., stored inside the file system) of size +.I 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) +.TP +.BI fast_commit_size= fast-commit-size +Create an additional fast commit journal area of size +.I fast-commit-size +kilobytes. +This option is only valid if +.B fast_commit +feature is enabled +on the file system. If this option is not specified and if +.B fast_commit +feature is turned on, fast commit area size defaults to +.I journal-size +/ 64 megabytes. The total size of the journal with +.B fast_commit +feature set is +.I journal-size ++ ( +.I 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). +.TP +.BI location =journal-location +Specify the location of the journal. The argument +.I 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. +@JDEV@.TP +@JDEV@.BI device= external-journal +@JDEV@Attach the file system to the journal block device located on +@JDEV@.IR external-journal . +@JDEV@The external +@JDEV@journal must already have been created using the command +@JDEV@.IP +@JDEV@.B mke2fs -O journal_dev +@JDEV@.I external-journal +@JDEV@.IP +@JDEV@Note that +@JDEV@.I external-journal +@JDEV@must have been created with the +@JDEV@same block size as the new file system. +@JDEV@In addition, while there is support for attaching +@JDEV@multiple file systems to a single external journal, +@JDEV@the Linux kernel and +@JDEV@.BR e2fsck (8) +@JDEV@do not currently support shared external journals yet. +@JDEV@.IP +@JDEV@Instead of specifying a device name directly, +@JDEV@.I external-journal +@JDEV@can also be specified by either +@JDEV@.BI LABEL= label +@JDEV@or +@JDEV@.BI UUID= UUID +@JDEV@to locate the external journal by either the volume label or UUID +@JDEV@stored in the ext2 superblock at the start of the journal. Use +@JDEV@.BR dumpe2fs (8) +@JDEV@to display a journal device's volume label and UUID. See also the +@JDEV@.B -L +@JDEV@option of +@JDEV@.BR tune2fs (8). +.RE +@JDEV@.IP +@JDEV@Only one of the +@JDEV@.BR size " or " device +@JDEV@options can be given for a file system. +.TP +.BI \-l " filename" +Read the bad blocks list from +.IR filename . +Note that the block numbers in the bad block list must be generated +using the same block size as used by +.BR mke2fs . +As a result, the +.B \-c +option to +.B mke2fs +is a much simpler and less error-prone method of checking a disk for bad +blocks before formatting it, as +.B mke2fs +will automatically pass the correct parameters to the +.B badblocks +program. +.TP +.BI \-L " new-volume-label" +Set the volume label for the file system to +.IR new-volume-label . +The maximum length of the +volume label is 16 bytes. +.TP +.BI \-m " reserved-blocks-percentage" +Specify the percentage of the file system blocks reserved for +the super-user. This avoids fragmentation, and allows root-owned +daemons, such as +.BR syslogd (8), +to continue to function correctly after non-privileged processes are +prevented from writing to the file system. The default percentage +is 5%. +.TP +.BI \-M " last-mounted-directory" +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. +.TP +.B \-n +Causes +.B mke2fs +to not actually create a file system, but display what it +would do if it 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 +.B mke2fs +parameters that were passed when the +file system was originally created are used again. (With the +.B \-n +option added, of course!) +.TP +.BI \-N " number-of-inodes" +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 +.I bytes-per-inode +ratio). This allows the user to specify the number +of desired inodes directly. +.TP +.BI \-o " creator-os" +Overrides the default value of the "creator operating system" field of the +file system. The creator field is set by default to the name of the OS the +.B mke2fs +executable was compiled for. +.TP +.B "\-O \fR[^]\fIfeature\fR[,...]" +Create a file system with the given features (file system options), +overriding the default file system options. The features that are +enabled by default are specified by the +.I base_features +relation, either in the +.I [defaults] +section in the +.B /etc/mke2fs.conf +configuration file, +or in the +.I [fs_types] +subsections for the usage types as specified by the +.B \-T +option, further modified by the +.I features +relation found in the +.I [fs_types] +subsections for the file system and usage types. See the +.BR mke2fs.conf (5) +manual page for more details. +The file system type-specific configuration setting found in the +.I [fs_types] +section will override the global default found in +.IR [defaults] . +.sp +The file system feature set will be further edited +using either the feature set specified by this option, +or if this option is not given, by the +.I default_features +relation for the file system type being created, or in the +.I [defaults] +section of the configuration file. +.sp +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. +.TP +For more information about the features which can be set, please see +the manual page +.BR ext4 (5). +.TP +.B \-q +Quiet execution. Useful if +.B mke2fs +is run in a script. +.TP +.BI \-r " revision" +Set the file system revision for the new file system. Note that 1.2 +kernels only support revision 0 file systems. The default is to +create revision 1 file systems. +.TP +.B \-S +Write superblock and group descriptors only. This is an extreme +measure to be taken 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 +.B mke2fs +to reinitialize the superblock and group descriptors, while not +touching the inode table and the block and inode bitmaps. The +.B e2fsck +program should be run immediately 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 +.B 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. +.\" .TP +.\" .BI \-t " test" +.\" Check the device for bad blocks before creating the file system +.\" using the specified test. +.TP +.BI \-t " fs-type" +Specify the file system type (i.e., ext2, ext3, ext4, etc.) that is +to be created. +If this option is not specified, +.B 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 +.B /etc/mke2fs.conf +file. This option controls which file system options are used by +default, based on the +.B fstypes +configuration stanza in +.BR /etc/mke2fs.conf . +.sp +If the +.B \-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 supported by the requested +.IR fs-type . +(e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a +file system that is not supported by the ext3 implementation as found in +the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR" +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.) +.TP +.BI \-T " usage-type[,...]" +Specify how the file system is going to be used, so that +.B mke2fs +can choose optimal file system parameters for that use. The usage +types that are supported are defined in the configuration file +.BR /etc/mke2fs.conf . +The user may specify one or more usage types +using a comma separated list. +.sp +If this option is is not specified, +.B 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, +.B mke2fs +will use the file system type +.IR floppy . +If the file system size is greater than or equal to 3 but less than +512 megabytes, +.BR mke2fs (8) +will use the file system type +.IR small . +If the file system size is greater than or equal to 4 terabytes but less than +16 terabytes, +.BR mke2fs (8) +will use the file system type +.IR big . +If the file system size is greater than or equal to 16 terabytes, +.BR mke2fs (8) +will use the file system type +.IR huge . +Otherwise, +.BR mke2fs (8) +will use the default file system type +.IR default . +.TP +.BI \-U " UUID" +Set the universally unique identifier (UUID) of the file system to +.IR UUID . +The format of the UUID is a series of hex digits separated by hyphens, +like this: +"c1b9d5a2-f162-11cf-9ece-0020afc76f16". +The +.I UUID +parameter may also be one of the following: +.RS 1.2i +.TP +.I clear +clear the file system UUID +.TP +.I random +generate a new randomly-generated UUID +.TP +.I time +generate a new time-based UUID +.RE +.TP +.B \-v +Verbose execution. +.TP +.B \-V +Print the version number of +.B mke2fs +and exit. +.TP +.BI \-z " undo_file" +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 undo_file argument, the undo file will be written to a file named +mke2fs-\fIdevice\fR.e2undo in the directory specified via the +\fIE2FSPROGS_UNDO_DIR\fR environment variable or the \fIundo_dir\fR directive +in the configuration file. + +WARNING: The undo file cannot be used to recover from a power or system crash. +.SH ENVIRONMENT +.TP +.B MKE2FS_SYNC +If set to non-zero integer value, its value is used to determine how often +.BR sync (2) +is called during inode table initialization. +.TP +.B MKE2FS_CONFIG +Determines the location of the configuration file (see +.BR mke2fs.conf (5)). +.TP +.B MKE2FS_FIRST_META_BG +If set to non-zero integer value, its value is used to determine first meta +block group. This is mostly for debugging purposes. +.TP +.B MKE2FS_DEVICE_SECTSIZE +If set to non-zero integer value, its value is used to determine logical +sector size of the +.IR device . +.TP +.B MKE2FS_DEVICE_PHYS_SECTSIZE +If set to non-zero integer value, its value is used to determine physical +sector size of the +.IR device . +.TP +.B MKE2FS_SKIP_CHECK_MSG +If set, do not show the message of file system automatic check caused by +mount count or check interval. +.SH AUTHOR +This version of +.B mke2fs +has been written by Theodore Ts'o . +.SH AVAILABILITY +.B mke2fs +is part of the e2fsprogs package and is available from +http://e2fsprogs.sourceforge.net. +.SH SEE ALSO +.BR mke2fs.conf (5), +.BR badblocks (8), +.BR dumpe2fs (8), +.BR e2fsck (8), +.BR tune2fs (8), +.BR ext4 (5) -- cgit v1.2.3