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Building the LTSP Server for PXE Boot Thin Clients on Ubuntu 24.04

By lordfrancs3

Building the LTSP Server for PXE Boot Thin Clients on Ubuntu 24.04 In Part 1, we introduced the design for a centralized Linux thin client solution using LTSP, LDAP, NFS, XFCE, Google Chrome kiosk mode, and Apache Guacamole. In this second part, we will build the LTSP server that allows client machines to boot from the network using PXE and iPXE. This article focuses on the LTSP server foundation. The goal is to prepare an Ubuntu 24.04 server, install LTSP, configure network boot services, generate a client image, and test the first PXE boot. LDAP authentication, shared user home directories, desktop behavior, kiosk mode, Guacamole, security hardening, and Ansible automation will be covered in later parts of this series. What We Are Building in This Part The LTSP server will provide the boot environment for thin clients. A client machine will power on, request network boot information, load iPXE, receive the LTSP boot menu, and start the Linux client environment from the LTSP server. The basic boot flow looks like this: Thin Client | | PXE boot request v Network DHCP server | | IP address assignment v LTSP Server with Proxy DHCP | | iPXE boot files v LTSP Client Image | v Linux desktop login screen This setup uses a proxy DHCP model. That means the existing router or DHCP server can continue assigning IP addresses. The LTSP server only provides the network boot details needed by PXE clients. This is useful when you do not want to replace the current DHCP service in an office, classroom, or lab network. Why Use LTSP LTSP provides an integrated solution for network booting Linux clients using iPXE, image management, and centralized configuration. Compared to manually combining PXE, TFTP, NFS, and boot scripts, LTSP simplifies deployment and maintenance by managing these components together. For more details, see: https://ltsp.org/docs/ Why Use Proxy DHCP Proxy DHCP allows integration into existing networks without replacing the current DHCP server. This avoids disruption and reduces the risk of configuration conflicts. Why Use dnsmasq dnsmasq provides proxy DHCP, TFTP, and optional DNS in a single lightweight service. Alternatives such as ISC DHCP and standalone TFTP servers require more complex configuration. Important note: On Ubuntu 24.04, dnsmasq can conflict with the system’s native DNS resolver (systemd-resolved). By default, systemd-resolved listens on port 53, which dnsmasq may also attempt to use if DNS functionality is enabled. In this LTSP setup, dnsmasq is only used for proxy DHCP and TFTP, not DNS. The LTSP helper (ltsp dnsmasq) configures dnsmasq in proxy DHCP mode, which avoids DNS binding. If needed, explicitly disable DNS: sudo nano /etc/dnsmasq.conf Add or confirm: port=0 Then restart dnsmasq: sudo systemctl restart dnsmasq Why Use iPXE iPXE supports advanced boot features such as HTTP booting, scripting, and improved hardware compatibility compared to traditional PXE firmware. Why Use NFS NFS is used to serve the LTSP client image because it is efficient and well-supported for Linux network filesystems. Why Use XFCE XFCE is lightweight and performs well on older or low-resource thin clients. Why Use LightDM LightDM is lightweight and easy to configure for thin client environments. Why Remove Snap Snap is removed to maintain a consistent APT-based package environment and avoid automatic Snap dependencies. Target Environment Item Example value Server OS Ubuntu 24.04 LTS Server hostname ltsp01 Server IP address 192.168.100.137 Network 192.168.100.0/24 Existing DHCP server Router or firewall LTSP mode Proxy DHCP Client boot method PXE or UEFI network boot Client desktop Basic XFCE login screen Browser Google Chrome Stable in a later part Snap Not used Replace the sample IP addresses with your own network values. Ubuntu 24.04 LTS is supported with standard security maintenance until 31 May 2029. See: https://documentation.ubuntu.com/release-notes/24.04/ Before You Start You need: One Ubuntu 24.04 server At least one test client or virtual machine that can boot from PXE A wired network connection An existing DHCP server on the network Internet access on the LTSP server Root or sudo access Step 1: Prepare the Ubuntu 24.04 Server Start with a clean Ubuntu 24.04 installation. Update the system: sudo apt update sudo apt upgrade -y Install basic tools: sudo apt install -y software-properties-common curl wget gnupg ca-certificates Set the hostname: sudo hostnamectl set-hostname ltsp01 Check the IP address: ip addr Step 2: Remove Snap from the Base Server Remove Snap: sudo apt purge snapd -y sudo apt autoremove --purge -y Prevent Snap from being reinstalled: cat <<'EOF' | sudo tee /etc/apt/preferences.d/nosnap.pref Package: snapd Pin: release * Pin-Priority: -10 EOF Step 3: Add the LTSP PPA sudo add-apt-repository ppa:ltsp/ppa -y sudo apt update See: https://ltsp.org/docs/installation/ Step 4: Install LTSP and Required Packages sudo apt install --install-recommends -y \ ltsp ltsp-binaries dnsmasq nfs-kernel-server \ openssh-server squashfs-tools ethtool net-tools epoptes \ lightdm lightdm-gtk-greeter xfce4 \ xserver-xorg-core xinit x11-xserver-utils Add your admin user to epoptes: sudo gpasswd -a administrator epoptes Step 5: Configure LightDM for XFCE sudo mkdir -p /etc/lightdm/lightdm.conf.d sudo nano /etc/lightdm/lightdm.conf.d/50-xfce.conf [Seat:*] greeter-session=lightdm-gtk-greeter greeter-hide-users=true greeter-show-manual-login=true user-session=xfce allow-guest=false Restart: sudo systemctl restart lightdm Step 6: Configure LTSP Proxy DHCP sudo ltsp dnsmasq sudo systemctl restart dnsmasq Step 7: Generate the LTSP Client Image sudo ltsp image / See: https://ltsp.org/man/ltsp/ Step 8: Generate the iPXE Boot Menu sudo ltsp ipxe Step 9: Configure NFS for LTSP sudo ltsp nfs sudo systemctl restart nfs-kernel-server Step 10: Generate the LTSP Initrd Configuration sudo ltsp initrd See: https://ltsp.org/man/ltsp.conf/ Step 11: Check the LTSP Services systemctl status dnsmasq --no-pager systemctl status nfs-kernel-server --no-pager systemctl status ssh --no-pager Step 12: Boot the First PXE Client Set client boot order: Network Boot / PXE Boot first Disk boot second The client should reach the LightDM login screen. Step 13: Create a Temporary Local Test User sudo adduser testuser Rebuild: sudo ltsp image / sudo ltsp initrd Step 14: Updating the LTSP Image After Changes sudo ltsp image / If configuration changes: sudo ltsp initrd Troubleshooting The client does not get an IP address Check the DHCP server. The client gets an IP address but does not boot LTSP Check dnsmasq. dnsmasq fails to start Ensure port=0 is set in /etc/dnsmasq.conf. The client boots but fails to load the image Check NFS. The client reaches the login screen but login fails Use a local test user. Changes do not appear on the client Rebuild the LTSP image. What We Completed We built the base LTSP server on Ubuntu 24.04. What Comes Next Part 3 will cover centralized authentication and user home directories. References LTSP Documentation https://ltsp.org/docs/ LTSP Installation Guide https://ltsp.org/docs/installation/ LTSP Manual https://ltsp.org/man/ltsp/ LTSP Configuration Manual https://ltsp.org/man/ltsp.conf/ Ubuntu 24.04 LTS Release Notes https://documentation.ubuntu.com/release-notes/24.04/ Ubuntu Server Documentation https://documentation.ubuntu.com/server/ Ubuntu Chromium Browser Package https://packages.ubuntu.com/noble/chromium-browser Google Linux Software Repositories https://www.google.com/linuxrepositories/