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docs/alpha/components/mhvtl/mhvtl-Installation-Guide.md

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+# mhvtl Installation and Configuration Guide for Ubuntu 24.04
+
+## 1. Introduction
+
+This guide provides step-by-step instructions for installing the mhvtl (Virtual Tape Library) from source on Ubuntu 24.04. The configuration files will be moved to a custom directory: `/opt/calypso/conf/mhvtl`.
+
+**Disclaimer:** Installing `mhvtl` involves compiling a kernel module. This process is complex and can be risky. If your kernel is updated, you will need to recompile and reinstall the `mhvtl` kernel module. Proceed with caution and at your own risk.
+
+## 2. Prerequisites
+
+First, update your package lists and install the necessary build tools and libraries.
+
+```bash
+sudo apt-get update
+sudo apt-get install -y git build-essential lsscsi sg3-utils zlib1g-dev liblzo2-dev linux-headers-$(uname -r)
+```
+
+## 3. Shell Environment
+
+Ubuntu uses `dash` as the default shell, which can cause issues during the `mhvtl` compilation. Temporarily switch to `bash`.
+
+```bash
+sudo rm /bin/sh
+sudo ln -s /bin/bash /bin/sh
+```
+
+## 4. Download and Compile
+
+### 4.1. Download the Source Code
+
+Clone the `mhvtl` repository from GitHub.
+
+```bash
+git clone https://github.com/markh794/mhvtl.git
+cd mhvtl
+```
+
+### 4.2. Compile and Install the Kernel Module
+
+```bash
+cd kernel
+make
+sudo make install
+sudo depmod -a
+sudo modprobe mhvtl
+```
+
+### 4.3. Compile and Install User-Space Daemons
+
+```bash
+cd ..
+make
+sudo make install
+```
+
+## 5. Configuration
+
+### 5.1. Create the Custom Configuration Directory
+
+Create the new configuration directory and move the default configuration files.
+
+```bash
+sudo mkdir -p /opt/calypso/conf/mhvtl
+sudo mv /etc/mhvtl/* /opt/calypso/conf/mhvtl/
+sudo rm -rf /etc/mhvtl
+```
+
+### 5.2. Systemd Service Configuration
+
+The `mhvtl` installation includes a systemd service file. We need to create an override file to tell the service to use the new configuration directory. The `mhvtl` service file typically uses an environment variable `VTL_CONFIG_PATH` to specify the configuration path.
+
+```bash
+sudo mkdir -p /etc/systemd/system/mhvtl.service.d
+sudo bash -c 'cat > /etc/systemd/system/mhvtl.service.d/override.conf <<EOF
+[Service]
+Environment="VTL_CONFIG_PATH=/opt/calypso/conf/mhvtl"
+EOF'
+```
+
+## 6. Starting and Verifying Services
+
+Reload the systemd daemon, start the `mhvtl` services, and check their status.
+
+```bash
+sudo systemctl daemon-reload
+sudo systemctl enable mhvtl.target
+sudo systemctl start mhvtl.target
+sudo systemctl status mhvtl.target
+```
+
+You can also use `lsscsi -g` to see if the virtual tape library is recognized.
+
+## 7. Reverting Shell
+
+After the installation is complete, you can revert the shell back to `dash`.
+
+```bash
+sudo dpkg-reconfigure dash
+```
+
+Select "No" when asked to use `dash` as the default shell.