mke2fs.conf(5)mke2fs.conf(5)NAMEmke2fs.conf - Configuration file for mke2fs
DESCRIPTIONmke2fs.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 filesystems.
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 exam‐
ple 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 spa‐
ces. 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 charac‐
ter).
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 an 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.
THE [options] STANZA
The following relations are defined in the [options] stanza.
proceed_delay
If this relation is set to a positive integer, then if mke2fs
will proceed after waiting proceed_delay seconds, after asking
the user for permission to proceed, 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.
THE [defaults] STANZA
The following relations are defined in the [defaults] stanza.
base_features
This relation specifies the filesystems features which are
enabled in newly created filesystems. It may be overridden by
the base_features relation found in the filesystem or usage type
subsection of the [fs_types] stanza.
default_features
This relation specifies a set of features that should be added
or removed to the features listed in the base_features relation.
It may be overridden by the filesystem-specific default_features
in the filesystem or usage type subsection of [fs_types], and by
the -O command-line option to mke2fs(8).
enable_periodic_fsck
This boolean relation specifies whether periodic filesystem
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).
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
filesystem image because the inode table isn't being initialized
lazily.
fs_type
This relation specifies the default filesystem 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
filesystem type, mke2fs will use a default filesystem 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 filesystem-type specific sec‐
tion of the configuration file does not specify a default value.
THE [fs_types] STANZA
Each tag in the [fs_types] stanza names a filesystem type or usage type
which can be specified via the -t or -T options to mke2fs(8), respec‐
tively.
The mke2fs program constructs a list of fs_types by concatenating the
filesystem 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 filesystem 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 filesys‐
tem type of ext4 will be used. If the filesystem 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 filesystem 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 filesystem, 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, result‐
ing in a filesystem feature set consisting of the sparse_super, file‐
type, dir_index, extents_and flex_bg features.
For each filesystem type, the following tags may be used in that
fs_type's subsection. These tags may also be used in the default sec‐
tion:
base_features
This relation specifies the features which are initially enabled
for this filesystem type. Only one base_features will be used,
so if there are multiple entries in the fs_types list whose sub‐
sections define the base_features relation, only the last will
be used by mke2fs(8).
errors Change the behavior of the kernel code when errors are detected.
In all cases, a filesystem error will cause e2fsck(8) to check
the filesystem on the next boot. errors can be one of the fol‐
lowing:
continue Continue normal execution.
remount-ro Remount filesystem 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 con‐
structed filesystem. 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.
default_features
This relation specifies set of features which should be enabled
or disabled after applying the features listed in the base_fea‐
tures 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 filesystem initializa‐
tion noticeably, but it requires the kernel to finish initializ‐
ing the filesystem in the background when the filesystem is
first mounted.
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 filesystem
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 filesystems with hashed b-tree directories. Valid algo‐
rithms 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 filesystem. This improves meta-data locality and perfor‐
mance on meta-data heavy workloads. The number of groups must
be a power of 2 and may only be specified if the flex_bg
filesystem feature is enabled.
options
This relation specifies additional extended options which should
be treated by mke2fs(8) as if they were prepended to the argu‐
ment of the -E option. This can be used to configure the
default extended options used by mke2fs(8) on a per-filesystem
type basis.
discard
This boolean relation specifies whether the mke2fs(8) should
attempt to discard device prior to filesystem 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 meta‐
data 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_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 mul‐
tiple of the requested alignment. If this relation is not spec‐
ified, no alignment requirement will be imposed on the huge
files.
hugefiles_align_disk
This relations specifies whether the alignment should be rela‐
tive 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.
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 dis‐
card/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.
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 ALSOmke2fs(8)E2fsprogs version 1.43.7 October 2017 mke2fs.conf(5)
