mke2fs.conf(5) File Formats Manual mke2fs.conf(5)
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 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.
[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 filesystem types. The filesystem type can be specified
explicitly using the -T option to mke2fs(8).
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 does 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.
blocksize
This relation specifies the default blocksize if the user does
not specify a blocksize on the command line, and the filesystem-
type specific section of the configuration file does not specify
a blocksize.
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.
inode_ratio
This relation specifies the default inode ratio if the user does
not specify one on the command line, and the filesystem-type
specific section of the configuration file does not specify a
default inode ratio.
inode_size
This relation specifies the default inode size if the user does
not specify one on the command line, and the filesystem-type
specific section of the configuration file does not specify a
default inode size.
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, and the filesystem-type specific sec-
tion of the configuration file does not specify a default
reserved ratio. This value can be a floating point number.
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.
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 is speci-
fies a set of changes to the features used by the filesystem, and which
is cumulative. So in the above example, first the configuration rela-
tion 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 fea-
ture, resulting in a filesystem feature set consisting of the
sparse_super, filetype, resize_inode, dir_index, extents_and flex_bg
features.
For each filesystem type, the following tags may be used in that
fs_type's subsection:
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).
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 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.
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)
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)
E2fsprogs version 1.42.9 December 2013 mke2fs.conf(5)
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