DragonFly On-Line Manual Pages
NEWFS_HAMMER(8) DragonFly System Manager's Manual NEWFS_HAMMER(8)
newfs_hammer -- construct a new HAMMER file system
newfs_hammer -L label [-Efh] [-b bootsize] [-m savesize] [-u undosize]
[-C cachesize[:readahead]] [-V version] special ...
The newfs_hammer utility creates a HAMMER file system on device(s)
special. If multiple devices are specified a single HAMMER file system
is created which spans all of them. Each special will constitute a vol-
ume which the HAMMER file system is built on. The first special speci-
fied becomes the root-volume with volume# 0. HAMMER file systems are
sector-size agnostic, however the DragonFly implementation requires the
sector size to be no larger than 16KB. HAMMER file systems start at a
relative offset of 0 and may only be created under out-of-band disk
labels (disklabel64(5) or gpt(8) labels), or in disklabel32(5) partitions
which do not overlap the label area (have a starting sector greater than
HAMMER file systems are designed for large storage systems, up to 1
Exabyte, and will not operate efficiently on small storage systems. The
minimum recommended file system size is 50GB. HAMMER must reserve 512MB
to 1GB of its storage for reblocking and UNDO/REDO FIFO. In addition,
HAMMER file systems operating normally, with full history retention and
daily snapshots, do not immediately reclaim space when files are deleted.
A regular system maintenance job runs once a day by periodic(8) to handle
HAMMER works best when the machine's normal workload would not otherwise
fill the file system up in the course of 60 days of operation.
The options are as follows:
All HAMMER file systems must be named and names should be unique
on a per-machine basis, although newfs_hammer does not prevent
from making file systems with the same label.
-f Force operation. This is needed for the creation of a HAMMER
file system less than 10GB size or with less than 512MB UNDO/REDO
FIFO. This should not be used under normal circumstances.
-E Use TRIM to erase the device's data before creating the file sys-
tem. The underlying device must have the TRIM sysctl enabled.
Only devices that support TRIM will have such a sysctl option
-h Show usage.
Specify a fixed area in which a boot related kernel and data can
be stored. This area is currently unused. The bootsize is spec-
ified in bytes with a suffix of K, M, G or T.
Specify a fixed area which HAMMER may use as a memory log. This
area is currently unused. The savesize is specified in bytes
with a suffix of K, M, G or T.
Specify the size of the fixed UNDO/REDO FIFO. The undosize is
specified in bytes with a suffix of K, M, G or T. By default
0.1% of the root volume's size is used, with a reasonable minimum
and a reasonable cap. The UNDO/REDO FIFO is used to sequence
meta-data out to the media for instant crash recovery.
Refer to the same option in hammer(8).
Specify the HAMMER file system version to format. By default
newfs_hammer formats the file system using the highest production
version number supported by the HAMMER VFS by checking the
vfs.hammer.supported_version sysctl. If you need to maintain
compatibility with an older version of HAMMER you may specify the
version with this option.
The bootsize, savesize and undosize must be given with a suffix of K, M,
G or T meaning kilobyte, megabyte, gigabyte and terabyte. Lower case can
also be used for suffix.
The newfs_hammer utility exits 0 on success, and >0 if an error occurs.
Create a file system named `HOME' on /dev/ad0s1d:
newfs_hammer -L HOME /dev/ad0s1d
Create a file system named `TEMP' on /dev/ad0s1d and /dev/ad1s1d:
newfs_hammer -L TEMP /dev/ad0s1d /dev/ad1s1d
disklabel32(5), disklabel64(5), HAMMER(5), fdisk(8), gpt(8), hammer(8),
The newfs_hammer utility first appeared in DragonFly 1.11.
Matthew Dillon <email@example.com>
DragonFly 4.7 December 16, 2016 DragonFly 4.7