4 ms·
Wouldn't dd'ing /dev/zero create an FS hole in your target file on many file systems? A similar (but maybe not isomorphic) situation in the Michael Kerrisk book
by tomsthumb 9y ago
Wouldn't dd'ing /dev/zero create an FS hole in your target file on many file systems? A similar (but maybe not isomorphic) situation in the Michael Kerrisk book is one of the excercises, and I'd bet ZFS does similar but suddenly we've assumed a lot of context.
- exikyut 9y agoGood question. The 0th-step answer is that the people using `dd` are generally going to be using all OS defaults, including for the filesystem. For what it's worth, I know that dd'ing /dev/zero makes df show a smaller value. AFAIK, df (for ext4 in my case) isn't reading a logical abstraction of capacity as arbitrarily decided upon by a bunch of layers, but is straightforwardly reporting the free blocks on disk.