On Sun, Oct 31, 2010 at 11:12:41 +0100, Alex Bligh <alex@xxxxxxxxxxx> wrote: > I want to generate or extend a large file in an ext4 filesystem allocating > space (i.e. not creating a sparse file) but not actually writing any data. > I realise that this will result in the file containing the contents of > whatever was there on the disk before, which is a possible security problem > in some circumstances, but it isn't a problem here. There isn't going to be a way to do that through the file system, because as you note it is a security problem. What is the high level thing you are trying to accomplish here? Modifying the filesystem offline seems risky and maybe there is a safer way to accomplish your goals. > Supplementary question: can I assume that if a non-sparse file is on disk > and never opened, and never unlinked, then the sectors used to to store > that file's data will never change irrespective of other operations on the > ext4 filesystem? IE nothing is shuffling where ext4 files are stored. I think SSDs will move stuff around at a very low level. They would look like they are at the same place to stuff access the device like a disk, but physically would be stored in a different hardware location. With normal disks, you'd only see this if the device got a read error, but was able to successfully read a marginal sector and remap it to a spare sector. But again, stuff talking to the disk will see it at the same address. _______________________________________________ Ext3-users mailing list Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
