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Comment by nikisweeting | Hacker News Reader

Article is pretty unclear, "copying" can mean many things to many different people:

    cp -r / /Volumes/Clone  # this never worked

    # what about rsync, does this still work?
    rsync --acls --archive --hard-links --one-file-system --sparse --xattrs / /Volumes/CLONE
    sudo bless -folder /Volumes/CLONE/System/Library/CoreServices

    # what about block-level copying, does this still work?
    sudo dd if=/dev/rdisk2 of=/dev/rdisk4 bs=1m conv=notrunc

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It’s documented in their older blog posts, I believe they use the ‘asr’ utility to copy the OS install. The many partitions that make up a macOS install means that cp or rsync isn’t enough. dd would do it, but at great cost in flexibility (can’t back up to a smaller disk, or select files) and speed

> dd would do it, but at great cost in flexibility (can’t back up to a smaller disk, or select files) and speed

I mean if we are talking about copying the whole OS or disk, that is a very macro operation. The fine-tuning can be done at the target location after copy like removing unwanted files/resizing partitions etc. No idea how slow would dd be but I thought you could specify larger blocksize for better performance (hoping someone more knowledgeable on dd can add their views).

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