add installing erlang page

Home.md

@@ -1,12 +1,19 @@
 # Gajumaru Wiki: Home
 
-## Quick Reference
+## Contents
 
-1. [[API Encoding]]: `ak_...` etc garbage explained
+### IT Support
-2. [[BaseN]]: Given `xy_ABCD`, what is the `ABCD`
+
-3. [[RLP]]: If the binary `ABCD` is some data with fields (e.g. a transaction),
+- [[Installing Erlang]]
+
+### Serialization
+
+- [[API Encoding]]: `ak_...` etc garbage explained
+- [[BaseN]]: Given `xy_ABCD`, what is the `ABCD`
+- [[RLP]]: If the binary `ABCD` is some data with fields (e.g. a transaction),
   how to destructure the binary data to fields
-4. [[Serializations]]: Conventions for field order in Gajumaru data structures
+- [[Serializations]]: Conventions for field order in Gajumaru data structures
+
 
 ## Principles
 

Installing-Erlang.md

@@ -0,0 +1,65 @@
+# Installing Erlang and zx/zomp
+
+Last updated: September 23, 2025 (PRH).
+
+## Linux
+
+### Ubuntu
+
+Source: [*Building Erlang 26.2.5 on Ubuntu 24.04*](https://zxq9.com/archives/2905)
+
+Adapt this to your Linux distribution.
+
+1.  **Install necessary build tools**
+
+    ```bash
+    sudo apt update
+    sudo apt upgrade
+    sudo apt install \
+        gcc curl g++ dpkg-dev build-essential automake autoconf \
+        libncurses-dev libssl-dev flex xsltproc libwxgtk3.2-dev \
+        wget vim git
+    ```
+
+2.  **Put [Kerl](https://github.com/kerl/kerl) somewhere
+    in your `$PATH`**. This is a tool to build Erlang releases.
+
+    ```bash
+    wget -O ~/bin/kerl https://raw.githubusercontent.com/kerl/kerl/master/kerl
+    chmod u+x ~/bin/kerl
+    ```
+
+3.  **Build Erlang from source using Kerl**
+
+    ```bash
+    kerl update releases
+    ## use the most recent one that looks stable
+    ## you do need to type the number twice, that's not a typo
+    kerl build 28.1 28.1
+    kerl install 28.1 ~/.erts/28.1
+    ```
+
+4.  **Put Erlang in your `$PATH`**
+
+    Update .bashrc or .zshrc or whatever with the following line:
+
+    ```bash
+    . $HOME/.erts/28.1/activate
+    ```
+
+
+5.  **Install zx**
+
+    ```bash
+    wget -q https://zxq9.com/projects/zomp/get_zx && bash get_zx
+    ```
+
+6.  **Test zx works**
+
+    zx installs itself to `~/bin`, so make sure that's in your
+    `$PATH`.
+
+    ```bash
+    zx run erltris
+    ```
+