btrfs-progs/Documentation/mkfs.btrfs.txt

mkfs.btrfs(8)
=============

NAME
----
mkfs.btrfs - create a btrfs filesystem

SYNOPSIS
--------
'mkfs.btrfs'
$$[-A|--alloc-start <alloc-start>]$$
$$[-b|--byte-count <byte-count>]$$
$$[-d|--data <data-profile>]$$
$$[-f|--force]$$
$$[-n|--nodesize <nodesize>]$$
$$[-l|--leafsize <leafsize>]$$
$$[-L|--label <label>]$$
$$[-m|--metadata <metadata profile>]$$
$$[-M|--mixed]$$
$$[-s|--sectorsize <sectorsize>]$$
$$[-r|--rootdir <rootdir>]$$
$$[-K|--nodiscard]$$
$$[-O|--features <feature1>[<,feature2...>]]$$
$$[-h]$$
$$[-V|--version]$$
$$<device> [<device>...]$$

DESCRIPTION
-----------
'mkfs.btrfs'
is used to create a btrfs filesystem (usually in a disk partition, or an array
of disk partitions).

<device>
is the special file corresponding to the device (e.g /dev/sdXX ).
If multiple devices are specified, btrfs is created
spanning across the specified  devices.

OPTIONS
-------
-A|--alloc-start <offset>::
Specify the offset from the start of the device to start the btrfs filesystem. The default value is zero, or the start of the device.

-b|--byte-count <size>::
Specify the size of the resultant filesystem. If this option is not used,
mkfs.btrfs uses all the available storage for the filesystem.

-d|--data <type>::
Specify how the data must be spanned across the devices specified. Valid
values are 'raid0', 'raid1', 'raid5', 'raid6', 'raid10' or 'single'.

-f|--force::
Force overwrite when an existing filesystem is detected on the device.
By default, mkfs.btrfs will not write to the device if it suspects that 
there is a filesystem or partition table on the device already.

-n|--nodesize <size>
+
-l|--leafsize <size>::
Specify the nodesize, the tree block size in which btrfs stores
data. The default value is 16KB (16384) or the page size, whichever is
bigger. Must be a multiple of the sectorsize, but not larger than
65536. Leafsize always equals nodesize and the options are aliases.

-L|--label <name>::
Specify a label for the filesystem.
+
NOTE: <name> should be less than 256 characters.


-m|--metadata <profile>::
Specify how metadata must be spanned across the devices specified. Valid
values are 'raid0', 'raid1', 'raid5', 'raid6', 'raid10', 'single' or 'dup'.
+
Single device
will have dup set by default except in the case of SSDs which will default to
single. This is because SSDs can remap blocks internally so duplicate blocks
could end up in the same erase block which negates the benefits of doing
metadata duplication.

-M|--mixed::
Mix data and metadata chunks together for more efficient space 
utilization.  This feature incurs a performance penalty in
larger filesystems.  It is recommended for use with filesystems
of 1 GiB or smaller.

-s|--sectorsize <size>::
Specify the sectorsize, the minimum data block allocation unit.
+
The default
value is the page size. If the sectorsize differs from the page size, the
created filesystem may not be mountable by current kernel. Therefore it is not
recommended to use this option unless you are going to mount it on a system
with the appropriate page size.

-r|--rootdir <rootdir>::
Specify a directory to copy into the newly created btrfs filesystem.
+
NOTE: '-r' option is done completely in userland, and don't need root
privilege to mount the filesystem.

-K|--nodiscard::
Do not perform whole device TRIM operation by default.

-O|--features <feature1>[,<feature2>...]::
A list of filesystem features turned on at mkfs time. Not all features are
supported by old kernels.
+
To see all features run::::
mkfs.btrfs -O list-all

-V|--version::
Print the 'mkfs.btrfs' version and exit.

-h::
Print help.

UNIT
----
As default the unit is the byte, however it is possible to append a suffix
to the arguments like 'k' for KBytes, 'm' for MBytes...

AVAILABILITY
------------
'btrfs' is part of btrfs-progs. Btrfs filesystem is currently under heavy
development,
and not suitable for any uses other than benchmarking and review.
Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for
further details.

SEE ALSO
--------
`btrfs`(8)