mke2fs: add support to align hugefiles relative to beginning of the disk

[thirdparty/e2fsprogs.git] / misc / mke2fs.conf.5.in

.\" -*- nroff -*-
.\" Copyright 2006 by Theodore Ts'o.  All Rights Reserved.
.\" This file may be copied under the terms of the GNU Public License.
.\" 
.TH mke2fs.conf 5 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
.SH NAME
mke2fs.conf \- Configuration file for mke2fs
.SH DESCRIPTION
.I mke2fs.conf
is the configuration file for 
.BR mke2fs (8).  
It controls the default parameters used by 
.BR mke2fs (8)
when it is creating ext2, ext3, or ext4 filesystems.
.PP
The
.I 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.   
.\" Tags can be assigned multiple values
An example of the INI-style format used by this configuration file 
follows below:
.P
	[section1]
.br
		tag1 = value_a
.br
		tag1 = value_b
.br
		tag2 = value_c
.P
	[section 2]
.br
		tag3 = {
.br
			subtag1 = subtag_value_a
.br
			subtag1 = subtag_value_b
.br
			subtag2 = subtag_value_c
.br
		}
.br
		tag1 = value_d
.br
		tag2 = value_e
.br
	}
.P
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.
.P
Tags and values must be quoted using double quotes if they contain
spaces.  Within a quoted string, the standard backslash interpretations 
apply: "\en" (for the newline character), 
"\et" (for the tab character), "\eb" (for the backspace character), 
and "\e\e" (for the backslash character).
.P
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.
.P
The following stanzas are used in the 
.I mke2fs.conf
file.  They will be described in more detail in future sections of this
document.
.TP
.I [options]
Contains relations which influence how mke2fs behaves.
.TP
.I [defaults]
Contains relations which define the default parameters
used by
.BR mke2fs (8).
In general, these defaults may be overridden by a definition in the
.B fs_types
stanza, or by an command-line option provided by the user.
.TP 
.I [fs_types]
Contains relations which define defaults that should be used for specific
filesystem types.  The filesystem type can be specified explicitly using
the 
.B -T
option to
.BR mke2fs (8).
.SH THE [options] STANZA
The following relations are defined in the
.I [options]
stanza.
.TP
.I proceed_delay
If this relation is set to a positive integer, then if mke2fs will
proceed after waiting
.I 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.
.SH THE [defaults] STANZA
The following relations are defined in the 
.I [defaults]
stanza.
.TP
.I base_features
This relation specifies the filesystems features which are enabled in
newly created filesystems.  It may be overridden by the
.I base_features
relation found in the filesystem or usage type subsection of
the
.I [fs_types] 
stanza.
.TP
.I default_features
This relation specifies a set of features that should be added or
removed to the features listed in the
.I base_features
relation.  It may be overridden by the filesystem-specific 
.I default_features
in the filesystem or usage type subsection of
.IR [fs_types] ,
and by the 
.B -O
command-line option
to 
.BR mke2fs (8).
.TP
.I 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
.B -i
and
.B -c
command-line options to
.BR tune2fs (8).
.TP
.I force_undo
This boolean relation, if set to a value of true, forces
.B 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.
.TP
.I fs_type
This relation specifies the default filesystem type if the user does not
specify it via the
.B \-t
option, or if
.B mke2fs
is not started using a program name of the form
.BI mkfs. fs-type\fR.
If both the user and the
.B mke2fs.conf
file does not specify a default filesystem type, mke2fs will use a
default filesystem type of
.IR ext3
if a journal was requested via a command-line option, or
.I ext2
if not.
.TP
.I blocksize
This relation specifies the default blocksize if the user does not
specify a blocksize on the command line, and the filesystem-type
specific section of the configuration file does not specify a blocksize.
.TP
.I hash_alg
This relation specifies the default hash algorithm used for the
new filesystems with hashed b-tree directories.  Valid algorithms
accepted are:
.IR legacy ,
.IR half_md4 ,
and
.IR tea .
.TP
.I 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.
.TP
.I 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.
.TP
.I 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.
.TP
.I undo_dir
This relation specifies the directory where the undo file should be
stored.  It can be overridden via the
.B E2FSPROGS_UNDO_DIR
environment variable.  If the directory location is set to the value
.IR none ,
.B mke2fs
will not create an undo file.
.SH THE [fs_types] STANZA
Each tag in the
.I [fs_types] 
stanza names a filesystem type or usage type which can be specified via the
.B \-t
or
.B \-T
options to
.BR mke2fs (8),
respectively.
.P
The
.B 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,
.B mke2fs
will look for a subsection in the
.I [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
.B mke2fs.conf
fragment:
.P
[defaults]
.br
	base_features = sparse_super,filetype,resize_inode,dir_index
.br
	blocksize = 4096
.br
	inode_size = 256
.br
	inode_ratio = 16384
.br

.br
[fs_types]
.br
	ext3 = {
.br
		features = has_journal
.br
	}
.br
	ext4 = {
.br
		features = extents,flex_bg
.br
		inode_size = 256
.br
	}
.br
	small = {
.br
		blocksize = 1024
.br
		inode_ratio = 4096
.br
	}
.br
	floppy = {
.br
		features = ^resize_inode
.br
		blocksize = 1024
.br
		inode_size = 128
.br
	}
.P
If mke2fs started with a program name of
.BR 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
.B mke2fs
will use a default
usage type of
.IR floppy .
This results in an fs_types list of "ext4, floppy".   Both the ext4
subsection and the floppy subsection define an
.I 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.
.P
The exception to this resolution is the
.I 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
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, resize_inode, dir_index,
extents_and flex_bg features.
.P
For each filesystem type, the following tags may be used in that 
fs_type's subsection:
.TP
.I base_features
This relation specifies the features which are initially enabled for this
filesystem type.  Only one
.I base_features
will be used, so if there are multiple entries in the fs_types list
whose subsections define the
.I base_features
relation, only the last will be used by
.BR mke2fs (8).
.TP
.I 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
.B -O
command-line option to
.BR mke2fs (8);
that is, a feature can be prefixed by a caret ('^') symbol to disable
a named feature.  Each
.I feature
relation specified in the fs_types list will be applied in the order
found in the fs_types list.
.TP
.I default_features
This relation specifies set of features which should be enabled or 
disabled after applying the features listed in the
.I base_features
and
.I features
relations.  It may be overridden by the
.B -O
command-line option to
.BR mke2fs (8).
.TP
.I auto_64-bit_support
This relation is a boolean which specifies whether
.BR 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.
.TP
.I 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
.B -o
command-line option to
.BR tune2fs (8).
.TP
.I blocksize
This relation specifies the default blocksize if the user does not
specify a blocksize on the command line.
.TP
.I 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 fully initialized by 
.BR 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.
.TP
.I journal_location
This relation specifies the location of the journal.
.TP
.I num_backup_sb
This relation indicates whether file systems with the
.B sparse_super2
feature enabled should be created with 0, 1, or 2 backup superblocks.
.TP
.I 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.
.TP
.I inode_ratio
This relation specifies the default inode ratio if the user does not
specify one on the command line.
.TP
.I inode_size
This relation specifies the default inode size if the user does not
specify one on the command line.
.TP
.I 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.
.TP
.I hash_alg
This relation specifies the default hash algorithm used for the
new filesystems with hashed b-tree directories.  Valid algorithms
accepted are:
.IR legacy ,
.IR half_md4 ,
and
.IR tea .
.TP
.I 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.
.TP
.I options
This relation specifies additional extended options which should be
treated by
.BR mke2fs (8)
as if they were prepended to the argument of the
.B -E
option.  This can be used to configure the default extended options used
by
.BR mke2fs (8)
on a per-filesystem type basis.
.TP
.I discard
This boolean relation specifies whether the
.BR mke2fs (8)
should attempt to discard device prior to filesystem creation.
.TP
.I cluster_size
This relation specifies the default cluster size if the bigalloc file
system feature is enabled.  It can be overridden via the
.B \-C
command line option to
.BR mke2fs (8)
.TP
.I make_hugefiles
This boolean relation enables the creation of pre-allocated files as
part of formatting the file system.
.TP
.I hugefiles_uid
This relation controls the user ownership for all of the files and
directories created by the
.I make_hugefiles
feature.
.TP
.I hugefiles_gid
This relation controls the group ownership for all of the files and
directories created by the
.I make_hugefiles
feature.
.TP
.I hugefiles_umask
This relation specifies the umask used when creating the files and
directories by the
.I make_hugefiles
feature.
.TP
.I 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
.I hugefiles_size
relation is non-zero, then
.I make_hugefiles
will create as many huge files as can fit to fill the entire file system.
.TP
.I hugefiles_slack
This relation specifies how much space should be reserved for other
files.
.TP
.I 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.
.TP
.I 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.
.TP
.I 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.
.TP
.I hugefiles_name
This relation specifies the base file name for the huge files.
.TP
.I hugefiles_digits
This relation specifies the (zero-padded) width of the field for the
huge file number.
.TP
.I zero_hugefiles
This boolean relation specifies whether or not zero blocks will be
written to the hugefiles while
.BR 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
.I 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.
.SH THE [devices] STANZA
Each tag in the
.I [devices] 
stanza names device name so that per-device defaults can be specified.
.TP
.I fs_type
This relation specifies the default parameter for the
.B \-t
option, if this option isn't specified on the command line.
.TP
.I usage_types
This relation specifies the default parameter for the
.B \-T
option, if this option isn't specified on the command line.
.SH FILES
.TP
.I /etc/mke2fs.conf
The configuration file for 
.BR mke2fs (8).
.SH SEE ALSO
.BR mke2fs (8)