Manual browser: mmcformat(8)

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


mmcformatformat optical media


mmcformat [-BDFGHhIMOpRrSsw] [-b blockingnr] [-c cert-num] special


The mmcformat utility formats optical media conforming to the MMC standard. This includes CD, DVD, and Blu-Ray (BD) media.

The options are as follows:

Blank media when possible before formatting it.
-b blockingnr
Explicitly select packet size in sectors (for CD-RW only). It is not recommended to change this from its default of 32.
-c cert-num
Certify media for DVD-RAM / DV-RE. The argument cert-num specifies:
no certification
full certification
quick certification
Debug mode. Print all SCSI/ATAPI command errors.
Format media.
Grow last CD-RW/DVD-RW session.
Show help and print formatting choices for the inserted media.
Show help and print formatting choices for the inserted media.
Show help and print formatting choices for the inserted media.
Select MRW (Mount Rainier) error correcting background format.
Old style CD-RW formatting; recommended for CD-RW.
Explicitly set packet format.
Restart previously stopped MCD-MRW or DVD+RW background format.
Recompile defect list for DVD-RAM.
Grow spare space DVD-RAM / BD-RE.
Format DVD+MRW / BD-RE with extra spare space.
Wait until completion of background format.


Due to the enormous varieties in optical media, mmcformat is made as generic as possible. This can result in confusion.


mmcformat -B -O /dev/rcd0d

Blanks and then formats a CD-RW disc using the “old style” format command. It is recommended to use this “old style” command unless your drive reports that it's not supported; in that case, resort to the default -F. Note that a CD-RW disc can be reformatted without being blanked. Blanking switches between sequential and fixed packet writing by erasing the disc. This can also help to revive old discs.

mmcformat -F -M /dev/rcd0d

Format a CD-RW or a DVD+RW to use MRW (Mount Rainier). This format tries to hide media flaws as much as possible by relocation.




The mmcformat command first appeared in NetBSD 5.0.


Reinoud Zandijk <>


mmcformat could be merged with scsictl(8) but that tool is very hard disk oriented.
May 9, 2008 NetBSD 7.0