Rename second-edition subfolder to `edition-2

blog/content/edition-2/extra/_index.md

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+title = "Extra Content"
+insert_anchor_links = "left"
+render = false
+sort_by = "weight"
+page_template = "edition-2/extra.html"
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blog/content/edition-2/extra/building-on-android/index.md

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+title = "Building on Android"
+weight = 3
+aliases = ["second-edition/extra/building-on-android/index.html"]
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+
+I finally managed to get `blog_os` building on my Android phone using [termux](https://termux.com/). This post explains the necessary steps to set it up.
+
+<!-- more -->
+
+<img src="building-on-android.png" alt="Screenshot of the compilation output from android" style="height: 50rem;" >
+
+
+### Install Termux and Nightly Rust
+
+First, install [termux](https://termux.com/) from the [Google Play Store](https://play.google.com/store/apps/details?id=com.termux) or from [F-Droid](https://f-droid.org/packages/com.termux/). After installing, open it and perform the following steps:
+
+- Install fish shell, set as default shell, and launch it:
+    ```
+    pkg install fish
+    chsh -s fish
+    fish
+    ```
+
+    This step is of course optional. However, if you continue with bash you will need to adjust some of the following commands to bash syntax.
+
+- Install some basic tools:
+    ```
+    pkg install wget tar
+    ```
+
+- Add the [community repository by its-pointless](https://wiki.termux.com/wiki/Package_Management#By_its-pointless):
+    ```
+    wget https://its-pointless.github.io/setup-pointless-repo.sh
+    bash setup-pointless-repo.sh
+    ```
+
+- Install cargo and a nightly version of rustc:
+    ```
+    pkg install rustc cargo rustc-nightly
+    ```
+
+- Prepend the nightly rustc path to your `PATH` in order to use nightly (fish syntax):
+    ```
+    set -U fish_user_paths $PREFIX/opt/rust-nightly/bin/ $fish_user_paths
+    ```
+
+Now `rustc --version` should work and output a nightly version number.
+
+### Install Git and Clone blog_os
+
+We need something to compile, so let's download the `blog_os` repository:
+
+- Install git:
+    ```
+    pkg install git
+    ```
+
+- Clone the `blog_os` repository:
+    ```
+    git clone https://github.com/phil-opp/blog_os.git
+    ```
+
+If you want to clone/push via SSH, you need to install the `openssh` package: `pkg install openssh`.
+
+### Install Xbuild and Bootimage
+
+Now we're ready to install `cargo xbuild` and `bootimage`
+
+- Run `cargo install`:
+    ```
+    cargo install cargo-xbuild bootimage
+    ```
+
+- Add the cargo bin directory to your `PATH` (fish syntax):
+    ```
+    set -U fish_user_paths ~/.cargo/bin/ $fish_user_paths
+    ```
+
+Now `cargo xbuild` and `bootimage` should be available. It does not work yet because `cargo xbuild` needs access to the rust source code. By default it tries to use rustup for this, but we have no rustup support so we need a different way.
+
+### Providing the Rust Source Code
+
+The Rust source code corresponding to our installed nightly is available in the [`its-pointless` repository](https://github.com/its-pointless/its-pointless.github.io):
+
+- Download a tar containing the source code:
+    ```
+    wget https://github.com/its-pointless/its-pointless.github.io/raw/master/rust-src-nightly.tar.xz
+    ```
+
+- Extract it:
+    ```
+    tar xf rust-src-nightly.tar.xz
+    ```
+
+- Set the `XARGO_RUST_SRC` environment variable to tell cargo-xbuild the source path (fish syntax):
+    ```
+    set -Ux XARGO_RUST_SRC ~/rust-src-nightly/rust-src/lib/rustlib/src/rust/src
+    ```
+
+Now cargo-xbuild should no longer complain about a missing `rust-src` component. However it will throw an I/O error after building the sysroot. The problem is that the downloaded Rust source code has a different structure than the source provided by rustup. We can fix this by adding a symbolic link:
+
+```
+ln -s ~/../usr/opt/rust-nightly/bin ~/../usr/opt/rust-nightly/lib/rustlib/aarch64-linux-android/bin
+```
+
+Now `cargo xbuild --target x86_64-blog_os.json` and `bootimage build` should both work!
+
+I couldn't get QEMU to run yet, so you won't be able to run your kernel. If you manage to get it working, please tell me :).