Ubuntu Manpage: mke2fs.conf - Configuration file for mke2fs

Provided by: e2fsprogs_1.44.1-1ubuntu1.4_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.

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).