message: doc: Switch back to instructions that use .tar.xz
diff: @@ -8,9 +8,9 @@ Writing the image on the SD card will take about 15 to 20 minutes for a 16GB ima
  ~~~sh
  sudo apt-get install xz-utils
  ~~~
  -* Unpack the .xz archive
  +* Unpack the .tar.xz archive
  ~~~sh
  - unxz name-of-the-image.xz
  + tar -xf name-of-the-image.tar.xz
  ~~~
  * Write the image on the SD card
  ~~~sh
  @@ -29,6 +29,6 @@ Note 2: It is very likely that the **dd** command will have to be executed with
  ## Windows
  -* Unpack the .xz archive using [7-Zip](https://www.7-zip.org/)
  +* Unpack the .tar.xz archive using [7-Zip](https://www.7-zip.org/)
  * Install the [balenaEtcher](https://www.balena.io/etcher/) app
  * Write the .img file to the SD card using the balenaEtcher app
  