sfdisk is a script-oriented tool for partitioning any block
device. It runs in interactive mode if executed on a terminal
(stdin refers to a terminal).
Since version 2.26 sfdisk supports MBR (DOS), GPT, SUN and SGI
disk labels, but no longer provides any functionality for CHS
(Cylinder-Head-Sector) addressing. CHS has never been important
for Linux, and this addressing concept does not make any sense
for new devices.
sfdisk protects the first disk sector when create a new disk
label. The option --wipe always disables this protection. Note
that fdisk(8) and cfdisk(8) completely erase this area by
default.
sfdisk (since version 2.26) aligns the start and end of
partitions to block-device I/O limits when relative sizes are
specified, when the default values are used or when
multiplicative suffixes (e.g., MiB) are used for sizes. It is
possible that partition size will be optimized (reduced or
enlarged) due to alignment if the start offset is specified
exactly in sectors and partition size relative or by
multiplicative suffixes.
The recommended way is not to specify start offsets at all and
specify partition size in MiB, GiB (or so). In this case sfdisk
aligns all partitions to block-device I/O limits (or when I/O
limits are too small then to megabyte boundary to keep disk
layout portable). If this default behaviour is unwanted (usually
for very small partitions) then specify offsets and sizes in
sectors. In this case sfdisk entirely follows specified numbers
without any optimization.
sfdisk does not create the standard system partitions for SGI and
SUN disk labels like fdisk(8) does. It is necessary to explicitly
create all partitions including whole-disk system partitions.
sfdisk uses BLKRRPART (reread partition table) ioctl to make sure
that the device is not used by system or other tools (see also
--no-reread). It's possible that this feature or another sfdisk
activity races with udevd. The recommended way how to avoid
possible collisions is to use --lock option. The exclusive lock
will cause udevd to skip the event handling on the device.
The sfdisk prompt is only a hint for users and a displayed
partition number does not mean that the same partition table
entry will be created (if -N not specified), especially for
tables with gaps.
