On Wed, 2008-06-25 at 11:02 -0500, Mikkel L. Ellertson wrote: > Patrick O'Callaghan wrote: > > On Wed, 2008-06-25 at 13:31 +0100, Dan Track wrote: > >> Thanks for the heads up on this. If the data blocks don't have > >> anything written into them, then what data is written into them when > >> using dd? if I restore the dd image will the blocks then be in the > >> same state i.e unwritten to? > >> > >> Also following on from this if I create a file using dd let's say 2GB, > >> how does the filesystem know that all these blocks belong to the file > >> myfile.img, and where is the information stored to say that a block > >> has data written into it or not? > > > > It's important to understand that this has nothing to do with 'dd', it's > > simply how the Unix filesystem works, and since Linux is "culturally > > derived" from Unix, it does the same thing. You would see the same > > effect just by using 'cp' or even 'cat'. > > > cp knows how to handle sparse files. From the cp man page: > > By default, sparse SOURCE files are detected by a crude heuristic > and the corresponding DEST file is made sparse as well. That is the > behavior selected by --sparse=auto. Specify --sparse=always to > create a sparse DEST file whenever the SOURCE file contains a long > enough sequence of zero bytes. Use --sparse=never to inhibit > creation of sparse files. > > So I would think that cp would give him a good copy... True. I've been using cp for more than 30 years so I hadn't looked at the man page in the last decade or two :-) poc -- fedora-list mailing list fedora-list@xxxxxxxxxx To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
