Create PXE bootable Proxmox installation

2020-10-26: successfully pxe-installed 6.2
2019-12-30: successfully pxe-installed 6.1
2018-08-27: successfully pxe-installed 5.2
2017-07-11: successfully pxe-installed 5.0 (despite #1)
2017-06-07: successfully ipxe-installed 4.4
2016-12-13: successfully pxe-installed 4.4
2016-09-27: successfully pxe-installed 4.3

Preparation

download Proxmox VE ISO Installer from Proxmox into a folder somewhere (e.g. /tmp/pve-iso)
run the script pve-iso-2-pxe.sh with the path to the ISO file as parameter (you need to be root or sudo for the loop mount)
the linux26 and initrd.iso.img (including ISO) will copied to the sub-directory pxeboot

iPXE (recommended)

copy/move linux26 and initrd.iso.img to a directory of your webserver (e.g. /var/www/proxmox/${version})

mofiy the ip adress of the server in the following ipxe bootscripct according to your setup:

#!ipxe
dhcp
set serverip http://192.168.1.1 //Modify this to match the ip adress or domain of your webserver
set pveversion 6.2 //Modify this to match the version you want to install
set opts "vga=791 video=vesafb:ywrap,mtrr ramdisk_size=16777216 rw quiet initrd=initrd.iso.img"
menu Please choose an operating system to boot
    item normal Install Proxmox
    item debug Install Proxmox (Debug Mode)
choose --default normal --timeout 5000 target && goto ${target}
:debug
    set kernel "${webserver}/proxmox/${pveversion}/linux26 ${opts} splash=verbose proxdebug"
    goto init
:normal
    set kernel "${webserver}/proxmox/${pveversion}/linux26 ${opts} splash=silent"
    goto init
:init
initrd ${webserver}/proxmox/${pveversion}/initrd.iso.img
chain ${kernel}

embed the bootscript into your ipxe build or start the script from ipxe using the chain command
be happy and think about supporting the great guys at Proxmox!

PXE (HTTP - faster)

on your PXE server, use lpxelinux.0 as pxelinux.0 (overwrite or set filename via DHCP option)
copy/move linux26 and initrd.iso.img to a directory of your webserver (e.g. /var/www/proxmox/${version})

add the following lines to your PXE config file (mind the important parameter ramdisk_size or the initrd won't fit into default memory):

label proxmox-install-http
        menu label Install Proxmox HTTP
        linux http://${webserver}/proxmox/${version}/linux26
        initrd http://${webserver}/proxmox/${version}/initrd.iso.img
        append vga=791 video=vesafb:ywrap,mtrr ramdisk_size=16777216 rw quiet splash=silent
        
label proxmox-install-http
        menu label Install Proxmox HTTP (Debug)
        linux http://${webserver}/proxmox/${version}/linux26
        initrd http://${webserver}/proxmox/${version}/initrd.iso.img
        append vga=791 video=vesafb:ywrap,mtrr ramdisk_size=16777216 rw quiet splash=silent proxdebug

be happy and think about supporting the great guys at Proxmox!

PXE (TFTP)

on your PXE server, create a directory proxmox/${version} in your PXE root directory (e.g. /var/lib/tftpboot/ or /srv/pxe/)
copy/move linux26 and initrd.iso.img to this directory