[PULL 2/9] docs/orangepi: Add instructions for resizing SD image to power of two

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

From: Niek Linnenbank <nieklinnenbank@gmail.com>

SD cards need to have a size of a power of two.
Update the Orange Pi machine documentation to include
instructions for resizing downloaded images using the
qemu-img command.

Signed-off-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20200712183708.15450-1-nieklinnenbank@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 docs/system/arm/orangepi.rst | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/docs/system/arm/orangepi.rst b/docs/system/arm/orangepi.rst
index c41adad488..6f23907fb6 100644
--- a/docs/system/arm/orangepi.rst
+++ b/docs/system/arm/orangepi.rst
@@ -127,6 +127,16 @@ can be downloaded from:
 Alternatively, you can also choose to build you own image with buildroot
 using the orangepi_pc_defconfig. Also see https://buildroot.org for more information.
 
+When using an image as an SD card, it must be resized to a power of two. This can be
+done with the qemu-img command. It is recommended to only increase the image size
+instead of shrinking it to a power of two, to avoid loss of data. For example,
+to prepare a downloaded Armbian image, first extract it and then increase
+its size to one gigabyte as follows:
+
+.. code-block:: bash
+
+  $ qemu-img resize Armbian_19.11.3_Orangepipc_bionic_current_5.3.9.img 1G
+
 You can choose to attach the selected image either as an SD card or as USB mass storage.
 For example, to boot using the Orange Pi PC Debian image on SD card, simply add the -sd
 argument and provide the proper root= kernel parameter:
@@ -213,12 +223,12 @@ Next, unzip the NetBSD image and write the U-Boot binary including SPL using:
   $ dd if=/path/to/u-boot-sunxi-with-spl.bin of=armv7.img bs=1024 seek=8 conv=notrunc
 
 Finally, before starting the machine the SD image must be extended such
-that the NetBSD kernel will not conclude the NetBSD partition is larger than
-the emulated SD card:
+that the size of the SD image is a power of two and that the NetBSD kernel
+will not conclude the NetBSD partition is larger than the emulated SD card:
 
 .. code-block:: bash
 
-  $ dd if=/dev/zero bs=1M count=64 >> armv7.img
+  $ qemu-img resize armv7.img 2G
 
 Start the machine using the following command:
 
-- 
2.21.3