I’ve been using dd to clone some disks recently, usually when they use filesystems macOS does not handle natively. macOS is a UNIX operating system; Linux is Unix-like, and their command-line tools are similar without being identical. Homebrew fills in plenty of the gaps. Thanks to Dave Jansen’s dd with progress indication on macOS, I also found a way to give these disk-level clones a proper progress display using Pipe Viewer (pv).

brew install pv

sudo dd if=/dev/rdiskX bs=1m | pv -s 2000G | sudo dd of=/dev/rdiskY bs=1m

The -s 2000G value tells pv the expected amount of data so it can calculate progress; it doesn’t limit how much gets copied. Treat it as a placeholder and match it to the actual size of your source. By default, G means gibibytes, so 2000G is not exactly the same as a drive advertised as 2 TB. And because this is dd: double-check which device is the input and which is the output before pressing Return. The output device will be overwritten.

On macOS, dd also prints its current input and output block counts when it receives SIGINFO, which you can normally request with Control-T in the terminal. I still like pv here because it gives me a continuous progress display.

And now I have some idea of where my clones are up to. Consider it noted down for future reference! 🙂

Sources