NEWFS_EXT2FS(8) System Manager's Manual NEWFS_EXT2FS(8)

newfs_ext2fsconstruct a new ext2 file system

newfs_ext2fs [-FINqZ] [-b block-size] [-D inodesize] [-f frag-size] [-i bytes-per-inode] [-m free-space] [-n inodes] [-O filesystem-format] [-S sector-size] [-s size] [-V verbose] [-v volnamespecial

newfs_ext2fs is used to initialize and clear ext2 file systems before first use. Before running newfs_ext2fs, the disk must be labeled using disklabel(8). newfs_ext2fs builds a file system on the specified special device, basing its defaults on the information in the disk label. Typically the defaults are reasonable, although newfs_ext2fs has numerous options to allow the defaults to be selectively overridden.

The special file should be a raw device, for example /dev/rsd0a; if a relative path like sd0a is specified, the corresponding raw device is used.

Options with numeric arguments may contain an optional (case-insensitive) suffix:

Bytes; causes no modification. (Default)
Kilo; multiply the argument by 1024.
Mega; multiply the argument by 1048576.
Giga; multiply the argument by 1073741824.

The following options define the general layout policies.

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:

<= 512 MB
1 KB
> 512 MB
4 KB
Set the inode size. Defaults to 128, and can also be set to 256 for compatibility with ext4.
Create a file system image in special. The file system size needs to be specified with “-s size”. No attempts to use or update the disk label will be made.
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.
Do not require that the file system type listed in the disk label is ‘ext2fs’.
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.
The percentage of space reserved from normal users; the minimum free space threshold. The default value used is 5%.
Causes the file system parameters to be printed out without really creating the file system.
This specifies the number of inodes for the file system. If both -i and -n are specified then -n takes precedence. The default number of inodes is calculated from a number of blocks in the file system.
Select the filesystem-format.

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)
DYNAMIC_REV’; various extended (and sometimes incompatible) features are enabled (though not all features are supported on OpenBSD). Currently only the following features are supported:

Prepare some reserved structures which enable future file system resizing.
Store file types in directory entries to improve performance.
Prepare superblock backups for the fsck_ext2fs(8) utility on not all but sparse block groups.
Enable files larger than 2G bytes.
Operate in quiet mode. Equivalent to -V 1.
The size of the file system in sectors. An ‘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 -S secsize) after suffix interpretation.

If no -s size is specified then the filesystem size defaults to that of the partition or, if -F is specified, the existing file.

If size is negative, the specified size is subtracted from the default size (reserving space at the end of the partition).

This controls the amount of information written to stdout:

No output.
Overall size and cylinder group details.
A progress bar (dots ending at right hand margin).
The first few super-block backup sector numbers are displayed before the progress bar.
All the super-block backup sector numbers are displayed (no progress bar).

The default is 4. If -N is specified, newfs_ext2fs stops before outputting the progress bar.

This specifies a volume name for the file system.
Pre-zeros the file system image created with -F. This is necessary if the image is to be used by vnd(4) (which doesn't support file systems with ‘holes’).

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 newfs_ext2fs 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 fsck_ext2fs(8) to find the alternative superblocks if the standard superblock is lost.

The size of a sector in bytes (almost never anything but 512). Defaults to 512.

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.

The file system is created with ‘random’ inode generation numbers to improve NFS security.

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.

For the newfs_ext2fs command to succeed, the disk label should first be updated such that the fstype field for the partition is set to ‘ext2fs’, unless -F or -I is used.

The partition size is found using 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 special references the same partition as the minor device number.

fstat(2), disklabel(5), disktab(5), fs(5), disklabel(8), fsck_ext2fs(8), mount(8), mount_ext2fs(8), newfs(8)

Remy Card, Theodore Ts'o, and Stephen Tweedie, Design and Implementation of the Second Extended Filesystem, The Proceedings of the First Dutch International Symposium on Linux,

The newfs_ext2fs command first appeared in OpenBSD 4.7.

The newfs_ext2fs command was written by Izumi Tsutsui <>.

The newfs_ext2fs command is still experimental and there are few sanity checks.

The newfs_ext2fs command doesn't have options to specify each REV1 file system feature independently.

The newfs_ext2fs command doesn't support the bad block list accounted by the bad blocks inode.

Many newer ext2 file system features (especially journaling) are not supported yet.

Some features in file systems created by the newfs_ext2fs command might not be recognized properly by the fsck_ext2fs(8) utility.

There is no native tool in the OpenBSD distribution for resizing ext2 file systems yet.

March 31, 2022 OpenBSD 7.5