Ltsp-manager/Preparation

Operating system
Currently, LTSP Manager is only available in recent Debian and Ubuntu releases. You'll need a desktop environment, so download the "desktop" and not the "server" .iso of those distributions.

If you have some 32bit clients, download the 32bit .iso, because the server installation is used as a template for the clients. Note that there's a kernel bug that causes issues on 32bit installations with > 8 GB RAM, so don't use 32bit when you have more than 8 GB RAM. On the other hand, if all your clients are 64bit, download the 64bit .iso.

Some desktop environments require OpenGL, which runs rather slow in LTSP thin clients. Namely, avoid Unity, Gnome 3 and Cinnamon if any of your clients boots in thin mode. The MATE desktop environment is a good choice if you have some thin clients. On the other hand, if all your clients boot in fat mode, you can use any desktop environment you like.

For example, you can install your server using this live CD.

Hardware specifications
Clients that have less than 500 MB RAM are automatically booted in "thin client mode". That means that all processes run on the server and the "screen" is transfered to the clients. And that in turn means that you need a good server because all the user applications will run there.

Clients that have more than 500 MB RAM are automatically booted in "fat client mode". That means that all processes run on the clients, and only the "disk data" comes from the server (i.e. the clients are of course diskless). And that in turn means that you don't need a good server.

The recommended method to run LTSP is with fat clients. Only use the thin client mode if you have ancient hardware like Pentium 3 (256 RAM minimum). The "500 MB RAM" limit is configurable via the FAT_RAM_THRESHOLD lts.conf variable.

Some formulas for the server specifications are: For example, for 10 thin clients you'd need 4500 MB RAM and 4500 passmark score, while for 10 fat clients you'd need 1800 MB RAM and 1800 passmark score.
 * RAM: 1500 + (30*N_FAT_CLIENTS) + (300*N_THIN_CLIENTS) MB RAM.
 * CPU: 1500 + (30*N_FAT_CLIENTS) + (300*N_THIN_CLIENTS) in [passmark points].

Network
You should use gigabit networking, at least in the server <=> switch connection. The clients <=> switch connection can be 100 Mbps without significant performance loss. But if you have mixed speed (1000/100) connections, try to put all the clients and the server in the same switch, i.e. avoiding chaining switches.

Traditionally, LTSP proposed a 2-NIC setup, with one interface facing the Internet and the other facing an "internal" switch where the LTSP clients are. LTSP Manager automatically supports this setup if you set the "internal" NIC IP to 192.168.67.1. But the most common setup, which is also the recommended one, is to have only one NIC, one switch, one subnet, and a router that runs a DHCP server. LTSP Manager automatically configures the LTSP server in "proxyDHCP" mode so that it sends the boot filename to the clients, but leaves the IP lease management to the router.