Date: Sun, 08 Jul 2012 23:27:23 -0400 From: "Thomas Mueller" <mueller23@insightbb.com> To: freebsd-questions@freebsd.org Cc: Carmel <carmel_ny@hotmail.com>, Polytropon <freebsd@edvax.de> Subject: Re: Format a USB flash drive using gpart Message-ID: <47.B3.06836.B9F4AFF4@smtp02.insight.synacor.com>
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On Sat, 07 Jul 2012 17:45:17 -0400, Thomas Mueller wrote: > Does a USB flash drive also work as a giant floppy, no partitions? > Can you make a flash drive bootable when nonpartitioned and > formatted that way? Polytropon responded: > Yes, that's exactly what my advice was aiming to, but let's > try to keep the terminology clean: You cannot do without > partitions. A partition carries a file system. > You _can_ do without slices. A slice holds one or more partitions. > A slice is a "DOS primary partition". Omitting it is called > "dedicated mode". There may be some circumstances where a > dedicated disk doesn't boot. Personally I haven't met one, > but it's still possible due to BIOSes expecting MS-DOS-alike > structures. > For the file system side, it's just a matter of having > created one partition covering the whole disk, newfs and > tunefs it, and install the boot code. Wojciech Puchar did > already explain how this works and which tools are involved. > However, there _is_ a way to make a "giant floppy without a > file system" (as you said without partitions, and I'll take > that literally): You can use tar, "the universal file system > that isn't a file system" to write data to the USB stick. > Writing stuff: > # tar cf /dev/da0 /my/files > Reading stuff: > # tar xf /dev/da0 > This works, but it may appear that no other system can read it. > If you consider using it for FreeBSD only, no problem. The big > advantage: You don't need to mount and umount the stick. > I'm assume _that_ construct cannot be booted. You mean the non-subdivided 1.44 MB or other capacity of a floppy is called a partition? Same question for CDs? One does not usually think of something that can't be created by subdividing as a partition. Also, a file system can be contained in an image file. Or is this a virtual partition? Might # tar xf /dev/da0 work in other BSDs or even other (quasi-)Unixes including Linux, using the appropriate device name where applicable in place of da0? While that particular construst could probably not be booted, it is possible to boot from a floppy or image file that does not contain a file system. Some of the disk images on the System Rescue CD (sysresccd.org) are not viewable/mountable as file systems. Tom
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