Document the trivial dd alternative when creating an SD image to avoid Etcher
**Is your feature request related to a problem? Please describe:**
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I didn’t trust giving _unknown to me_ 3rd party software elevated rights to copy your img onto an SD card

**Describe the solution you'd like:**
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Include the simple dd command alternative to Etcher

**Describe alternatives you've considered:**
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sudo dd if=Raspbian-Homebridge.img  of=/dev/disk4 _(where 4 is the appropriate device)_

**Additional context:**
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Agreed, I have to use elevated rights for block writes, but I trust dd already installed (on my MacOS). A one line alternative would help cautious users to adopt your great s/w.

It was a tedious Google search to find the alternative, I hope this feature rich request might help others. (Credit to https://www.reddit.com/r/homebridge/comments/dlct5d/homebridge_experience_with_raspberry_pi_zero_wh/ for the solution)
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