path: root/sbin/newfs_ext2fs/newfs_ext2fs.8

.\"	$OpenBSD: newfs_ext2fs.8,v 1.11 2022/03/31 17:27:20 naddy Exp $
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.Dd $Mdocdate: March 31 2022 $
.Dt NEWFS_EXT2FS 8
.Os
.Sh NAME
.Nm newfs_ext2fs
.Nd construct a new ext2 file system
.Sh SYNOPSIS
.Nm
.Bk -words
.Op Fl FINqZ
.Op Fl b Ar block-size
.Op Fl D Ar inodesize
.Op Fl f Ar frag-size
.Op Fl i Ar bytes-per-inode
.Op Fl m Ar free-space
.Op Fl n Ar inodes
.Op Fl O Ar filesystem-format
.Op Fl S Ar sector-size
.Op Fl s Ar size
.Op Fl V Ar verbose
.Op Fl v Ar volname
.Ar special
.Ek
.Sh DESCRIPTION
.Nm
is used to initialize and clear ext2 file systems before first use.
Before running
.Nm ,
the disk must be labeled using
.Xr disklabel 8 .
.Nm
builds a file system on the specified
.Ar special
device,
basing its defaults on the information in the disk label.
Typically the defaults are reasonable, although
.Nm
has numerous options to allow the defaults to be selectively overridden.
.Pp
The
.Ar special
file should be a raw device,
for example
.Pa /dev/rsd0a ;
if a relative path like
.Pa sd0a
is specified,
the corresponding raw device is used.
.Pp
Options with numeric arguments may contain an optional (case-insensitive)
suffix:
.Pp
.Bl -tag -width 3n -offset indent -compact
.It b
Bytes; causes no modification.
(Default)
.It k
Kilo; multiply the argument by 1024.
.It m
Mega; multiply the argument by 1048576.
.It g
Giga; multiply the argument by 1073741824.
.El
.Pp
The following options define the general layout policies.
.Bl -tag -width Ds
.It Fl b Ar block-size
The block size of the file system, in bytes.
It must be a power of two.
The smallest allowable size is 1024 bytes.
The default size depends upon the size of the file system:
.Pp
.Bl -tag -width "file system size" -compact -offset indent
.It Sy "file system size"
.Ar block-size
.It \*(Lt= 512 MB
1 KB
.It \*(Gt 512 MB
4 KB
.El
.It Fl D Ar inodesize
Set the inode size.
Defaults to 128, and can also be set to 256 for
compatibility with ext4.
.It Fl F
Create a file system image in
.Ar special .
The file system size needs to be specified with
.Dq Fl s Ar size .
No attempts to use or update the disk label will be made.
.It Fl f Ar frag-size
The fragment size of the file system in bytes.
It must be the same as the blocksize,
because the current ext2fs
implementation doesn't support fragmentation.
.It Fl I
Do not require that the file system type listed in the disk label is
.Ql ext2fs .
.It Fl i Ar bytes-per-inode
This specifies the density of inodes in the file system.
If fewer inodes are desired, a larger number should be used;
to create more inodes a smaller number should be given.
.It Fl m Ar free-space
The percentage of space reserved from normal users; the minimum free
space threshold.
The default value used is 5%.
.It Fl N
Causes the file system parameters to be printed out
without really creating the file system.
.It Fl n Ar inodes
This specifies the number of inodes for the file system.
If both
.Fl i
and
.Fl n
are specified then
.Fl n
takes precedence.
The default number of inodes is calculated from a number of blocks in
the file system.
.It Fl O Ar filesystem-format
Select the filesystem-format.
.Pp
.Bl -tag -width 3n -offset indent -compact
.It 0
.Ql GOOD_OLD_REV ;
this option is primarily used to build root file systems that can be
understood by old or dumb firmware for bootstrap.
(default)
.It 1
.Ql DYNAMIC_REV ;
various extended (and sometimes incompatible) features are enabled
(though not all features are supported on
.Ox ) .
Currently only the following features are supported:
.Pp
.Bl -tag -width "SPARSESUPER" -offset indent -compact
.It RESIZE
Prepare some reserved structures which enable future file system resizing.
.It FTYPE
Store file types in directory entries to improve performance.
.It SPARSESUPER
Prepare superblock backups for the
.Xr fsck_ext2fs 8
utility on not all but sparse block groups.
.It LARGEFILE
Enable files larger than 2G bytes.
.El
.El
.It Fl q
Operate in quiet mode.
Equivalent to
.Fl V Ar 1 .
.It Fl s Ar size
The size of the file system in sectors.
An
.Sq s
suffix will be interpreted as the number of sectors (the default).
All other suffixes are interpreted as per other numeric arguments,
except that the number is converted into sectors by dividing by the
sector size (as specified by
.Fl S Ar secsize )
after suffix interpretation.
.Pp
If no
.Fl s Ar size
is specified then the filesystem size defaults to that of the partition or,
if
.Fl F
is specified, the existing file.
.Pp
If
.Ar size
is negative, the specified size is subtracted from the default size
(reserving space at the end of the partition).
.It Fl V Ar verbose
This controls the amount of information written to stdout:
.Pp
.Bl -tag -width 3n -offset indent -compact
.It 0
No output.
.It 1
Overall size and cylinder group details.
.It 2
A progress bar (dots ending at right hand margin).
.It 3
The first few super-block backup sector numbers are displayed before the
progress bar.
.It 4
All the super-block backup sector numbers are displayed (no progress bar).
.El
.Pp
The default is 4.
If
.Fl N
is specified,
.Nm
stops before outputting the progress bar.
.It Fl v Ar volname
This specifies a volume name for the file system.
.It Fl Z
Pre-zeros the file system image created with
.Fl F .
This is necessary if the image is to be used by
.Xr vnd 4
(which doesn't support file systems with
.Sq holes ) .
.El
.Pp
The following option overrides the standard sizes for the disk geometry.
The default value is taken from the disk label.
Changing this default is useful only when using
.Nm
to build a file system whose raw image will eventually be used on a
different type of disk than the one on which it is initially created
(for example on a write-once disk).
Note that changing this value from its default will make it impossible for
.Xr fsck_ext2fs 8
to find the alternative superblocks if the standard superblock is lost.
.Bl -tag -width Ds
.It Fl S Ar sector-size
The size of a sector in bytes (almost never anything but 512).
Defaults to 512.
.El
.Sh NOTES
There is no option to specify the metadata byte order on the file system
to be created because the native ext2 file system is always little endian
even on big endian hosts.
.Pp
The file system is created with
.Sq random
inode generation numbers to improve NFS security.
.Pp
The owner and group IDs of the root node and reserved blocks of the new
file system are set to the effective UID and GID of the user initializing
the file system.
.Pp
For the
.Nm
command to succeed,
the disk label should first be updated such that the fstype field for the
partition is set to
.Ql ext2fs ,
unless
.Fl F
or
.Fl I
is used.
.Pp
The partition size is found using
.Xr fstat 2 ,
not by inspecting the disk label.
The block size and fragment size will be written back to the disk label
only if the last character of
.Ar special
references the same partition as the minor device number.
.Sh SEE ALSO
.Xr fstat 2 ,
.Xr disklabel 5 ,
.Xr disktab 5 ,
.Xr fs 5 ,
.Xr disklabel 8 ,
.\" .Xr dumpfs 8 ,
.Xr fsck_ext2fs 8 ,
.Xr mount 8 ,
.Xr mount_ext2fs 8 ,
.Xr newfs 8
.Rs
.%A Remy Card
.%A Theodore Ts'o
.%A Stephen Tweedie
.%T "Design and Implementation of the Second Extended Filesystem"
.%J "The Proceedings of the First Dutch International Symposium on Linux"
.%U http://e2fsprogs.sourceforge.net/ext2intro.html
.Re
.Sh HISTORY
The
.Nm
command first appeared in
.Ox 4.7 .
.Sh AUTHORS
The
.Nm
command was written by
.An Izumi Tsutsui
.Aq Mt tsutsui@NetBSD.org .
.Sh BUGS
The
.Nm
command is still experimental and there are few sanity checks.
.Pp
The
.Nm
command doesn't have options to specify each REV1 file system feature
independently.
.Pp
The
.Nm
command doesn't support the bad block list accounted by the bad blocks inode.
.Pp
Many newer ext2 file system features (especially journaling) are
not supported yet.
.Pp
Some features in file systems created by the
.Nm
command might not be recognized properly by the
.Xr fsck_ext2fs 8
utility.
.Pp
There is no native tool in the
.Ox
distribution for resizing ext2 file systems yet.