mke2fs.conf(5) — Linux manual page

NAME | DESCRIPTION | THE [options] STANZA | THE [defaults] STANZA | THE [fs_types] STANZA | THE [devices] STANZA | FILES | SEE ALSO | COLOPHON

mke2fs.conf(5)             File Formats Manual            mke2fs.conf(5)

NAME         top

       mke2fs.conf - Configuration file for mke2fs

DESCRIPTION         top

       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         top

       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         top

       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         top

       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         top

       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         top

       /etc/mke2fs.conf
              The configuration file for mke2fs(8).

SEE ALSO         top

       mke2fs(8)

COLOPHON         top

       This page is part of the e2fsprogs (utilities for ext2/3/4
       filesystems) project.  Information about the project can be found
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       ⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on
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E2fsprogs version 1.46.2      February 2021               mke2fs.conf(5)

Pages that refer to this page: ext4(5)mke2fs(8)