So apparently fdatasync is like fsync but doesn't sync the metadata, I can understand what the metadata refers to in case of like copying a file, but what if you are just zeroing a drive or writing random bytes to it? What does metadata mean?

1 Answer 1


In case you are writing to a block device, the inode is most likely stored in an virtual filesystem so there will never be any updates caused by dd, fsync would effectively be treated identically to fdatasync by the kernel. for normal files dd doesn't really set any metadata directly, only indirectly by virtue of dd's activity will the metadata will change (notably mtime and atime).

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