# uname -a
Linux <snip> 5.4.46 #1-NixOS SMP Wed Jun 10 18:24:58 UTC 2020 x86_64 GNU/Linux
# sfdisk --version
from util-linux 2.35.1
# sfdisk --unit=S  --dump /dev/sda | tee out.dump
label: dos
label-id: 0x6aacd6ae
device: /dev/sda
unit: sectors
sector-size: 512

/dev/sda1 : start=        2048, size=   122875904, type=83
# sfdisk --force /dev/sda < out.dump
Checking that no-one is using this disk right now ... FAILED

This disk is currently in use - repartitioning is probably a bad idea.
Umount all file systems, and swapoff all swap partitions on this disk.
Use the --no-reread flag to suppress this check.

Disk /dev/sda: 300 GiB, 322122547200 bytes, 629145600 sectors
Disk model: PersistentDisk  
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x6aacd6ae

Old situation:

Device     Boot Start       End   Sectors  Size Id Type
/dev/sda1        2048 122877951 122875904 58.6G 83 Linux

>>> Script header accepted.
>>> Script header accepted.
>>> Script header accepted.
>>> Script header accepted.
>>> line 5: unsupported command

New situation:
Disklabel type: dos
Disk identifier: 0x6aacd6ae

Device     Boot Start       End   Sectors  Size Id Type
/dev/sda1        2048 122877951 122875904 58.6G 83 Linux
Leaving.