Provided by: e2fsprogs_1.47.0-2.4~exp1ubuntu4.1_amd64 
NAME
mke2fs.conf - Configuration file for mke2fs
DESCRIPTION
mke2fs.conf is the configuration file for mke2fs(8). It controls the default parameters used by
mke2fs(8) when it is creating ext2, ext3, or ext4 file systems.
The mke2fs.conf file uses an INI-style format. Stanzas, or top-level sections, are delimited by square
braces: [ ]. Within each section, each line defines a relation, which assigns tags to values, or to a
subsection, which contains further relations or subsections. An example of the INI-style format used by
this configuration file follows below:
[section1]
tag1 = value_a
tag1 = value_b
tag2 = value_c
[section 2]
tag3 = {
subtag1 = subtag_value_a
subtag1 = subtag_value_b
subtag2 = subtag_value_c
}
tag1 = value_d
tag2 = value_e
}
Comments are delimited by a semicolon (';') or a hash ('#') character at the beginning of the comment,
and are terminated by the end of line character.
Tags and values must be quoted using double quotes if they contain spaces. Within a quoted string, the
standard backslash interpretations apply: "\n" (for the newline character), "\t" (for the tab character),
"\b" (for the backspace character), and "\\" (for the backslash character).
Some relations expect a boolean value. The parser is quite liberal on recognizing ``yes'', '`y'',
``true'', ``t'', ``1'', ``on'', etc. as a boolean true value, and ``no'', ``n'', ``false'', ``nil'',
``0'', ``off'' as a boolean false value.
The following stanzas are used in the mke2fs.conf file. They will be described in more detail in future
sections of this document.
[options]
Contains relations which influence how mke2fs behaves.
[defaults]
Contains relations which define the default parameters used by mke2fs(8). In general, these
defaults may be overridden by a definition in the fs_types stanza, or by a command-line option
provided by the user.
[fs_types]
Contains relations which define defaults that should be used for specific file system and usage
types. The file system type and usage type can be specified explicitly using the -tand-T options
to mke2fs(8), respectively.
[devices]
Contains relations which define defaults for specific devices.
THE [options] STANZA
The following relations are defined in the [options] stanza.
proceed_delay
If this relation is set to a positive integer, then mke2fs will wait proceed_delay seconds after
asking the user for permission to proceed and then continue, even if the user has not answered the
question. Defaults to 0, which means to wait until the user answers the question one way or
another.
sync_kludge
If this relation is set to a positive integer, then while writing the inode table, mke2fs will
request the operating system flush out pending writes to initialize the inode table every
sync_kludge block groups. This is needed to work around buggy kernels that don't handle
writeback throttling correctly.
THE [defaults] STANZA
The following relations are defined in the [defaults] stanza.
creator_os
This relation specifies the "creator operating system" for the file system unless it is overridden
on the command line. The default value is the OS for which the mke2fs executable was compiled.
fs_type
This relation specifies the default file system type if the user does not specify it via the -t
option, or if mke2fs is not started using a program name of the form mkfs.fs-type. If both the
user and the mke2fs.conf file do not specify a default file system type, mke2fs will use a default
file system type of ext3 if a journal was requested via a command-line option, or ext2 if not.
undo_dir
This relation specifies the directory where the undo file should be stored. It can be overridden
via the E2FSPROGS_UNDO_DIR environment variable. If the directory location is set to the value
none, mke2fs will not create an undo file.
In addition, any tags that can be specified in a per-file system tags subsection as defined below (e.g.,
blocksize, hash_alg, inode_ratio, inode_size, reserved_ratio, etc.) can also be specified in the defaults
stanza to specify the default value to be used if the user does not specify one on the command line, and
the file system-type specific section of the configuration file does not specify a default value.
THE [fs_types] STANZA
Each tag in the [fs_types] stanza names a file system type or usage type which can be specified via the
-t or -T options to mke2fs(8), respectively.
The mke2fs program constructs a list of fs_types by concatenating the file system type (i.e., ext2, ext3,
etc.) with the usage type list. For most configuration options, mke2fs will look for a subsection in the
[fs_types] stanza corresponding with each entry in the constructed list, with later entries overriding
earlier file system or usage types. For example, consider the following mke2fs.conf fragment:
[defaults]
base_features = sparse_super,filetype,resize_inode,dir_index
blocksize = 4096
inode_size = 256
inode_ratio = 16384
[fs_types]
ext3 = {
features = has_journal
}
ext4 = {
features = extents,flex_bg
inode_size = 256
}
small = {
blocksize = 1024
inode_ratio = 4096
}
floppy = {
features = ^resize_inode
blocksize = 1024
inode_size = 128
}
If mke2fs started with a program name of mke2fs.ext4, then the file system type of ext4 will be used. If
the file system is smaller than 3 megabytes, and no usage type is specified, then mke2fs will use a
default usage type of floppy. This results in an fs_types list of "ext4, floppy". Both the ext4
subsection and the floppy subsection define an inode_size relation, but since the later entries in the
fs_types list supersede earlier ones, the configuration parameter for fs_types.floppy.inode_size will be
used, so the file system will have an inode size of 128.
The exception to this resolution is the features tag, which specifies a set of changes to the features
used by the file system, and which is cumulative. So in the above example, first the configuration
relation defaults.base_features would enable an initial feature set with the sparse_super, filetype,
resize_inode, and dir_index features enabled. Then configuration relation fs_types.ext4.features would
enable the extents and flex_bg features, and finally the configuration relation fs_types.floppy.features
would remove the resize_inode feature, resulting in a file system feature set consisting of the
sparse_super, filetype, dir_index, extents_and flex_bg features.
For each file system type, the following tags may be used in that fs_type's subsection. These tags may
also be used in the default section:
base_features
This relation specifies the features which are initially enabled for this file system type. Only
one base_features will be used, so if there are multiple entries in the fs_types list whose
subsections define the base_features relation, only the last will be used by mke2fs(8).
enable_periodic_fsck
This boolean relation specifies whether periodic file system checks should be enforced at boot
time. If set to true, checks will be forced every 180 days, or after a random number of mounts.
These values may be changed later via the -i and -c command-line options to tune2fs(8).
errors 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. errors can be one of the
following:
continue Continue normal execution.
remount-ro Remount file system read-only.
panic Cause a kernel panic.
features
This relation specifies a comma-separated list of features edit requests which modify the feature
set used by the newly constructed file system. The syntax is the same as the -O command-line
option to mke2fs(8); that is, a feature can be prefixed by a caret ('^') symbol to disable a named
feature. Each feature relation specified in the fs_types list will be applied in the order found
in the fs_types list.
force_undo
This boolean relation, if set to a value of true, forces mke2fs to always try to create an undo
file, even if the undo file might be huge and it might extend the time to create the file system
image because the inode table isn't being initialized lazily.
default_features
This relation specifies set of features which should be enabled or disabled after applying the
features listed in the base_features and features relations. It may be overridden by the -O
command-line option to mke2fs(8).
auto_64-bit_support
This relation is a boolean which specifies whether mke2fs(8) should automatically add the 64bit
feature if the number of blocks for the file system requires this feature to be enabled. The
resize_inode feature is also automatically disabled since it doesn't support 64-bit block numbers.
default_mntopts
This relation specifies the set of mount options which should be enabled by default. These may be
changed at a later time with the -o command-line option to tune2fs(8).
blocksize
This relation specifies the default blocksize if the user does not specify a blocksize on the
command line.
lazy_itable_init
This boolean relation specifies whether the inode table should be lazily initialized. It only has
meaning if the uninit_bg feature is enabled. If lazy_itable_init is true and the uninit_bg
feature is enabled, the inode table will not be fully initialized by mke2fs(8). 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.
lazy_journal_init
This boolean relation specifies whether the journal inode should be lazily initialized. It only
has meaning if the has_journal feature is enabled. If lazy_journal_init is true, 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.
journal_location
This relation specifies the location of the journal.
num_backup_sb
This relation indicates whether file systems with the sparse_super2 feature enabled should be
created with 0, 1, or 2 backup superblocks.
packed_meta_blocks
This boolean relation specifies whether the allocation bitmaps, inode table, and journal should be
located at the beginning of the file system.
inode_ratio
This relation specifies the default inode ratio if the user does not specify one on the command
line.
inode_size
This relation specifies the default inode size if the user does not specify one on the command
line.
reserved_ratio
This relation specifies the default percentage of file system blocks reserved for the super-user,
if the user does not specify one on the command line.
hash_alg
This relation specifies the default hash algorithm used for the new file systems with hashed b-
tree directories. Valid algorithms accepted are: legacy, half_md4, and tea.
flex_bg_size
This relation specifies the number of block groups that will be packed together to create one
large virtual block group on 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 flex_bg file system feature is enabled.
options
This relation specifies additional extended options which should be treated by mke2fs(8) as if
they were prepended to the argument of the -E option. This can be used to configure the default
extended options used by mke2fs(8) on a per-file system type basis.
discard
This boolean relation specifies whether the mke2fs(8) should attempt to discard device prior to
file system creation.
cluster_size
This relation specifies the default cluster size if the bigalloc file system feature is enabled.
It can be overridden via the -C command line option to mke2fs(8)
make_hugefiles
This boolean relation enables the creation of pre-allocated files as part of formatting the file
system. The extent tree blocks for these pre-allocated files will be placed near the beginning of
the file system, so that if all of the other metadata blocks are also configured to be placed near
the beginning of the file system (by disabling the backup superblocks, using the
packed_meta_blocks option, etc.), the data blocks of the pre-allocated files will be contiguous.
hugefiles_dir
This relation specifies the directory where huge files are created, relative to the file system
root.
hugefiles_uid
This relation controls the user ownership for all of the files and directories created by the
make_hugefiles feature.
hugefiles_gid
This relation controls the group ownership for all of the files and directories created by the
make_hugefiles feature.
hugefiles_umask
This relation specifies the umask used when creating the files and directories by the
make_hugefiles feature.
num_hugefiles
This relation specifies the number of huge files to be created. If this relation is not
specified, or is set to zero, and the hugefiles_size relation is non-zero, then make_hugefiles
will create as many huge files as can fit to fill the entire file system.
hugefiles_slack
This relation specifies how much space should be reserved for other files.
hugefiles_size
This relation specifies the size of the huge files. If this relation is not specified, the
default is to fill the entire file system.
hugefiles_align
This relation specifies the alignment for the start block of the huge files. It also forces the
size of huge files to be a multiple of the requested alignment. If this relation is not
specified, no alignment requirement will be imposed on the huge files.
hugefiles_align_disk
This relations specifies whether the alignment should be relative to the beginning of the hard
drive (assuming that the starting offset of the partition is available to mke2fs). The default
value is false, which will cause hugefile alignment to be relative to the beginning of the file
system.
hugefiles_name
This relation specifies the base file name for the huge files.
hugefiles_digits
This relation specifies the (zero-padded) width of the field for the huge file number.
warn_y2038_dates
This boolean relation specifies whether mke2fs will issue a warning when creating a file system
with 128 byte inodes (and so therefore will not support dates after January 19th, 2038). The
default value is true, except for file systems created for the GNU Hurd since it only supports
128-byte inodes.
zero_hugefiles
This boolean relation specifies whether or not zero blocks will be written to the hugefiles while
mke2fs(8) is creating them. By default, zero blocks will be written to the huge files to avoid
stale data from being made available to potentially untrusted user programs, unless the device
supports a discard/trim operation which will take care of zeroing the device blocks. By setting
zero_hugefiles to false, this step will always be skipped, which can be useful if it is known that
the disk has been previously erased, or if the user programs that will have access to the huge
files are trusted to not reveal stale data.
encoding
This relation defines the file name encoding to be used if the casefold feature is enabled.
Currently the only valid encoding is utf8-12.1 or utf8, which requests the most recent Unicode
version; since 12.1 is the only available Unicode version, utf8 and utf8-12.1 have the same
result. encoding_flags This relation defines encoding-specific flags. For utf8 encodings, the
only available flag is strict, which will cause attempts to create file names containing invalid
Unicode characters to be rejected by the kernel. Strict mode is not enabled by default.
THE [devices] STANZA
Each tag in the [devices] stanza names device name so that per-device defaults can be specified.
fs_type
This relation specifies the default parameter for the -t option, if this option isn't specified on
the command line.
usage_types
This relation specifies the default parameter for the -T option, if this option isn't specified on
the command line.
FILES
/etc/mke2fs.conf
The configuration file for mke2fs(8).
SEE ALSO
mke2fs(8)