creating filesystem images

Gary W. Swearingen garys at
Wed Aug 24 17:45:34 GMT 2005

David Kelly <dkelly at> writes:

> The advantage of dump/restore is that only the necessary data is
> written. With dd all the unused blocks on the media are also written,
> including the filesystem, which will probably work on the larger card.

If you don't mind educating me further for no particular need...

I've long known about the UNIX concept of everything being a string of
bytes, but came to the conclusion early in my Linux days that disks
couldn't be used as a filesystem after a "dd" unless their cylinders
were the same size (or maybe it was just tracks).  Has this all gone
away with FreeBSD's removal of "block devices" and/or with LBA disks?

Can I get always (excepting un-related problems) get usable
filesystems after "dd if=/dev/ad1 of=/dev/ad1 bs=<almost anything>b"?
As a separate issue, some boot stuff can get messed up, right?  Or do
partition tables use LBA now too?  Seems like they'd have to, but I
don't remember reading about it anywhere.

> Tar or pax are not bad choices in addition to dump/restore.

bsdtar yes, but pax and gtar (tar in 4.x?) don't handle file flags,
if OP needs those.

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