mke2fs.conf - Configuration file for mke2fs
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 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 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 following relations are defined in the [defaults]
stanza.
- 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 section of the configuration file does not specify
a default value.
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), respectively.
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 filesystem 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, resulting in
a filesystem feature set consisting of the sparse_super, filetype,
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
section:
- 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 subsections define the
base_features relation, only the last will be used by
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).
- 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
following:
- features
- This relation specifies a comma-separated list of features edit requests
which modify the feature set used by the newly constructed 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.
- 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.
- 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
filesystem initialization noticeably, but it requires the kernel to finish
initializing the filesystem in the background when the filesystem 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 filesystem 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 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 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 filesystem.
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 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 argument 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 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 filesystem 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.
- 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.
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.
- /etc/mke2fs.conf
- The configuration file for mke2fs(8).