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 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 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.
- 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.
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.
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).
mke2fs(8)