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

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 delim‐
       ited  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  subsec‐
       tions.  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 charac‐
       ter), "\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  gen‐
              eral,  these  defaults may be overridden by a definition in the fs_types stanza, or
              by an command-line option provided by the user.

       [fs_types]
              Contains relations which define defaults that should be used for specific  filesys‐
              tem  types.  The filesystem type can be specified explicitly using the -T option to
              mke2fs(8).

THE [options] STANZA
       The following relations are defined in the [options] stanza.

       proceed_delay
              If this relation is set to a positive integer, then if mke2fs  will  proceed  after
              waiting  proceed_delay  seconds,  after  asking the user for permission to proceed,
              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.

THE [defaults] STANZA
       The following relations are defined in the [defaults] stanza.

       base_features
              This relation specifies the filesystems features which are enabled in newly created
              filesystems.  It may be overridden by  the  base_features  relation  found  in  the
              filesystem or usage type subsection of the [fs_types] stanza.

       default_features
              This  relation  specifies  a set of features that should be added or removed to the
              features listed in the  base_features  relation.   It  may  be  overridden  by  the
              filesystem-specific  default_features in the filesystem or usage type subsection of
              [fs_types], and by the -O command-line option to 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).

       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.

       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 does 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.

       blocksize
              This relation specifies the default blocksize if the user does not specify a block‐
              size  on the command line, and the filesystem-type specific section of the configu‐
              ration file does not specify a blocksize.

       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.

       inode_ratio
              This relation specifies the default inode ratio 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 inode ratio.

       inode_size
              This relation specifies the default inode size 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 inode size.

       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, and the
              filesystem-type specific section of the  configuration  file  does  not  specify  a
              default reserved ratio. This value can be a floating point number.

       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.

THE [fs_types] STANZA
       Each tag in the [fs_types] stanza names a filesystem type or usage type which can be spec‐
       ified 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 speci‐
       fied, 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 is 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  fea‐
       tures,  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, resize_inode, dir_index, extents_and flex_bg features.

       For each filesystem type, the following tags may be used in that fs_type's subsection:

       base_features
              This  relation specifies the features which are initially enabled for this filesys‐
              tem 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).

       features
              This relation specifies a comma-separated list of features edit requests which mod‐
              ify  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 speci‐
              fied in the fs_types list will be applied in the order found in the fs_types list.

       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 block‐
              size on the command line.

       lazy_itable_init
              This boolean relation specifies whether the inode table should be  lazily  initial‐
              ized.    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 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.

       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 specifes 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-filesys‐
              tem 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  fea‐
              ture 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 for‐
              matting the file system.

       hugefiles_uid
              This relation controls the user ownership for all of the files and directories cre‐
              ated 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 speci‐
              fied, 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
              Thie 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 if 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 num‐
              ber.

       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 writ‐
              ten 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 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).

SEE ALSO
       mke2fs(8)

E2fsprogs version 1.42.13                    May 2015                              mke2fs.conf(5)

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