USB vs PXE installer

Although our advanced usage documentation covers imaging via PXE, you will get your first box up and running quicker with less fuss using the USB installer. It’s also useful to bootstrap the PXE server.

We try to make the processes similar, and use as many of the same files as is practical.

In both cases the installer will install a preseeded image, reboot, run ansible and reboot again.

Hosting Files

Both USB and PXE booted installers need to get configuration files from somewhere.

The PXE solution is very opinionated. The PXE server controls all the things, hosts the files, we can assume it will work just fine.

The USB solution needs to make use of the exiting network.

There are many simple solutions, but they all have their downsides and your lan setup may make some easy or impossible. This section describes a few of the solutions. For more details see the Debian preseed page.

You will know you are having problems when the installer says: Failed to retrieve the preconfiguration file

There are 2 parts: where to host the files, and how the installer will reference them.

The default for USB is to run http_server.sh at the end of mk_usb_installer.sh and pass $hostname:8007 to the installer. This will work if the installer can resolve hostname.domain and wget the files from it.

If it can’t resolve, it may be the domain. Try .local or r use the IP address: 1.2.3.4:8007.

You can also host the files on some other server, using some other protocol, or put the files on the usb stick (this will requires editing some scripts to replace wget with cp.)

FAQ like things

PXE and USB are both boot devices which boot the same kernel, installer, which use the same preseed files and ansible playbooks to build up a box.

The goal is for both to share as much as possible, but there are some differences resulting in some duplication of settings and different behavior.

Both require a basic connection to the Internet.

Both take about the same amount of time (most of the time is spent downloading and decompressing .debs and writing to disk. Installing to an SSD is the best way to speed this up.

Differences:

PXE relies on a DHCP server sending parameters that reference a TFTP server.

PXE assumes the same server will host DHCP, TFTP and HTTP (sort of.)

PXE assumes you either know what disk is going to be wiped, or you don’t care and will try again if you get it wrong.

PXE can be 100% managed with ansible inventory files. (once you get it up and running, which is best done with a USB install.)

PXE requires collecting mac addresses and assigning hostnames in the ansible inventory files.

USB will prompt for some networking and disk parameters, and the HTTP server is configurable.

USB installer needs to get files from a local http server. Setting up the server is easy, resolving it from the installer doesn’t always “just work”.

Both support UEFI, but some systems won’t do UEFI PXE, in that case you have to use USB if you want an UEFI install.

USB is easier to get started with, PXE is nicer to work with.