doc: setup and support

1 files changed, 55 insertions, 0 deletions

diff --git a/README.md b/README.md
index 3ba80a1..09a4359 100644
--- a/README.md
+++ b/README.md
@@ -1,12 +1,67 @@
 # packer
+
 The rustkrazy image generator.
 
+# Supported hardware
+
+The images created by this program should work on the following machines:
+
+* Raspberry Pi 3 (any model)
+* Raspberry Pi 4 (any model)
+* x86_64 hardware supporting legacy boot
+
+UEFI support (for x86_64) is not planned, but contributions are welcome.
+
 # System package requirements
+
 For the packer to work you need to install the following packages:
 
 * nasm
 * squashfs-tools-ng
+* musl
+* (optional) clang
+* (optional) kernel-headers-musl
+
+If you want to build images for the Raspberry Pi, the aarch64 versions
+of the musl related packages (musl itself and optionally clang and the kernel headers)
+are required as well.
+
+Clang and the kernel headers are needed for some small sys crates to compile.
+Many crates will compile without them but there are a few that won't.
 
 Then, add the musl target:
 
 `rustup target add x86_64-unknown-linux-musl`
+
+# Supported crates
+
+Most Rust crates should compile if the packer is set up correctly.
+Larger sys crates that dynamically link to system libraries
+cannot easily be supported. Most notably OpenSSL is not supported.
+Check if your dependencies offer Cargo features to disable OpenSSL
+and replace it with rustls.
+
+In general simple crates are more likely to work
+but more complex crates can be built if the correct dependencies are installed.
+
+# Building the packer
+
+Make sure you have `cargo-make` installed:
+
+```
+cargo install cargo-make
+```
+
+Since the packer requires the compiled MBR for the x86_64 architecture
+it needs to be built by running:
+
+```
+cargo make
+```
+
+if you want to build x86_64 images.
+
+This assembles the MBR and builds the packer.
+
+You may skip this step if you're only interested in building images
+for the Raspberry Pi.