Ubuntu Manpage: mke2fs.conf - Configuration file for mke2fs

Provided by: e2fsprogs_1.45.5-2ubuntu1.2_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 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 [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.

       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.

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), 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:

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 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.

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).