Add install instructions for package managers

docs/build/install.md

@@ -1,3 +1,12 @@
+This document contains instructions for installing rippled.
+The APT package manager is common on Debian-based Linux distributions like
+Ubuntu,
+while the YUM package manager is common on Red Hat-based Linux distributions
+like CentOS.
+Installing from source is an option for all platforms,
+and the only supported option for installing custom builds.
+
+
 ## From source
 
 From a source build, you can install rippled and libxrpl using CMake's
@@ -11,3 +20,140 @@ The default [prefix][1] is typically `/usr/local` on Linux and macOS and
 `C:/Program Files/rippled` on Windows.
 
 [1]: https://cmake.org/cmake/help/latest/variable/CMAKE_INSTALL_PREFIX.html
+
+
+## With the APT package manager
+
+1. Update repositories:
+
+        sudo apt update -y
+
+2. Install utilities:
+
+        sudo apt install -y apt-transport-https ca-certificates wget gnupg
+
+3. Add Ripple's package-signing GPG key to your list of trusted keys:
+
+        sudo mkdir /usr/local/share/keyrings/
+        wget -q -O - "https://repos.ripple.com/repos/api/gpg/key/public" | gpg --dearmor > ripple-key.gpg
+        sudo mv ripple-key.gpg /usr/local/share/keyrings
+
+
+4. Check the fingerprint of the newly-added key:
+
+        gpg /usr/local/share/keyrings/ripple-key.gpg
+
+    The output should include an entry for Ripple such as the following:
+
+        gpg: WARNING: no command supplied.  Trying to guess what you mean ...
+        pub   rsa3072 2019-02-14 [SC] [expires: 2026-02-17]
+            C0010EC205B35A3310DC90DE395F97FFCCAFD9A2
+        uid           TechOps Team at Ripple <[email protected]>
+        sub   rsa3072 2019-02-14 [E] [expires: 2026-02-17]
+
+
+    In particular, make sure that the fingerprint matches. (In the above example, the fingerprint is on the third line, starting with `C001`.)
+
+4. Add the appropriate Ripple repository for your operating system version:
+
+        echo "deb [signed-by=/usr/local/share/keyrings/ripple-key.gpg] https://repos.ripple.com/repos/rippled-deb focal stable" | \
+            sudo tee -a /etc/apt/sources.list.d/ripple.list
+
+    The above example is appropriate for **Ubuntu 20.04 Focal Fossa**. For other operating systems, replace the word `focal` with one of the following:
+
+    - `jammy` for **Ubuntu 22.04 Jammy Jellyfish**
+    - `bionic` for **Ubuntu 18.04 Bionic Beaver**
+    - `bullseye` for **Debian 11 Bullseye**
+    - `buster` for **Debian 10 Buster**
+
+    If you want access to development or pre-release versions of `rippled`, use one of the following instead of `stable`:
+
+    - `unstable` - Pre-release builds ([`release` branch](https://github.com/ripple/rippled/tree/release))
+    - `nightly` - Experimental/development builds ([`develop` branch](https://github.com/ripple/rippled/tree/develop))
+
+    **Warning:** Unstable and nightly builds may be broken at any time. Do not use these builds for production servers.
+
+5. Fetch the Ripple repository.
+
+        sudo apt -y update
+
+6. Install the `rippled` software package:
+
+        sudo apt -y install rippled
+
+7. Check the status of the `rippled` service:
+
+        systemctl status rippled.service
+
+    The `rippled` service should start automatically. If not, you can start it manually:
+
+        sudo systemctl start rippled.service
+
+8. Optional: allow `rippled` to bind to privileged ports.
+
+    This allows you to serve incoming API requests on port 80 or 443. (If you want to do so, you must also update the config file's port settings.)
+
+        sudo setcap 'cap_net_bind_service=+ep' /opt/ripple/bin/rippled
+
+
+## With the YUM package manager
+
+1. Install the Ripple RPM repository:
+
+    Choose the appropriate RPM repository for the stability of releases you want:
+
+    - `stable` for the latest production release (`master` branch)
+    - `unstable` for pre-release builds (`release` branch)
+    - `nightly` for experimental/development builds (`develop` branch)
+
+    *Stable*
+
+        cat << REPOFILE | sudo tee /etc/yum.repos.d/ripple.repo
+        [ripple-stable]
+        name=XRP Ledger Packages
+        enabled=1
+        gpgcheck=0
+        repo_gpgcheck=1
+        baseurl=https://repos.ripple.com/repos/rippled-rpm/stable/
+        gpgkey=https://repos.ripple.com/repos/rippled-rpm/stable/repodata/repomd.xml.key
+        REPOFILE
+
+    *Unstable*
+
+        cat << REPOFILE | sudo tee /etc/yum.repos.d/ripple.repo
+        [ripple-unstable]
+        name=XRP Ledger Packages
+        enabled=1
+        gpgcheck=0
+        repo_gpgcheck=1
+        baseurl=https://repos.ripple.com/repos/rippled-rpm/unstable/
+        gpgkey=https://repos.ripple.com/repos/rippled-rpm/unstable/repodata/repomd.xml.key
+        REPOFILE
+
+    *Nightly*
+
+        cat << REPOFILE | sudo tee /etc/yum.repos.d/ripple.repo
+        [ripple-nightly]
+        name=XRP Ledger Packages
+        enabled=1
+        gpgcheck=0
+        repo_gpgcheck=1
+        baseurl=https://repos.ripple.com/repos/rippled-rpm/nightly/
+        gpgkey=https://repos.ripple.com/repos/rippled-rpm/nightly/repodata/repomd.xml.key
+        REPOFILE
+
+2. Fetch the latest repo updates:
+
+        sudo yum -y update
+
+3. Install the new `rippled` package:
+
+        sudo yum install -y rippled
+
+4. Configure the `rippled` service to start on boot:
+
+        sudo systemctl enable rippled.service
+
+5. Start the `rippled` service:
+
+        sudo systemctl start rippled.service