UEFI Boot has been supported on Dell PowerEdge servers since Generation 11 (~2010). But network booting via a PXE ROM to provision an OS is not a well know and established procedure, so I’ve been lazy and always placed my Dell PowerEdge servers in Legacy BIOS mode. Recently I was struggling with a R730 not accepting keyboard input on the PXELINUX menu, which felt like an issue with “Legacy USB emulation” not being enabled in the BIOS, but I couldn’t find any such setting. Therefore I decided it was time to bite the bullet and get UEFI Network boot working.

My first hurdle was not getting a IP from the DHCP server when attempting to network boot. The process went by so quickly, it felt like it wasn’t even waiting for a DHCP lease. With some help from our friendly local DHCP admin, we confirmed that it wasn’t even requesting one.

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Booting from PXE Device 1: Integrated NIC 1 Port 1 Partition 1
PXE: No media detected.
Boot Failed: PXE Device 1: Integrated NIC 1 Port 1 Partition 1

This particular server came with a “QLogic 57800 2x10Gb BT + 2x1Gb” network card. It turned out the firmware needed updating to make the network book functional. Downloading QLogic FastLinQ Network Adapter Device Firmware version 08.07.26 and applying it via the iDRAC solved the problem.

It is common to use pxelinux.0 as a bootloader for BIOS PXE ROM boots and traditionally your tftp root might look something like this:

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/var/lib/tftpboot
├── menu.c32
├── pxelinux.0
├── pxelinux.cfg
│   ├── default
│   └── 00:11:22:33:44:55
└── CentOS-7-x86_64
    ├── initrd.img
    ├── upgrade.img
    └── vmlinuz

pxelinux.0 and *.c32 are BIOS specific and therefore we need to supplement them with EFI compatible versions. All the required files can be found in the syslinux distribution hosted in the Kernel archives . At the time of writing, the latest version was 6.03.

  • For the bootloader, we require:
    • efi32/syslinux.efi from efi32/efi/syslinux.efi
    • efi32/ldlinux.e32 from efi32/com32/elflink/ldlinux/ldlinux.e32
    • efi64/syslinux.efi from efi64/efi/syslinux.efi
    • efi64/ldlinux.e64 from efi64/com32/elflink/ldlinux/ldlinux.e64
  • For the boot menu, we require:
    • efi32/menu.c32 from efi32/com32/menu/menu.c32
    • efi32/libutil.c32 from efi32/com32/libutil/libutil.c32
    • efi64/menu.c32 from efi64/com32/menu/menu.c32
    • efi64/libutil.c32 from efi64/com32/libutil/libutil.c32

The magic is that your pxelinux.cfg loads c32 modules relative to the bootloader directory (e.g. default menu.c32), therefore it’s possible to make a shared pxelinux.cfg configs as long as all the required modules have their own version relative to the bootloader. With a bit of reshuffling of the BIOS bootloaders and a sprinkling of symlinks, we end up with something like this:

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 /var/lib/tftpboot
 ├── bios
 │   ├── CentOS-7-x86_64 -> ../CentOS-7-x86_64
 │   ├── menu.c32
 │   ├── pxechain.com
 │   ├── pxelinux.0
 │   ├── pxelinux.cfg -> ../pxelinux.cfg
 ├── CentOS-7-x86_64
 │   ├── initrd.img
 │   ├── upgrade.img
 │   └── vmlinuz
 ├── efi32
 │   ├── CentOS-7-x86_64 -> ../CentOS-7-x86_64
 │   ├── ldlinux.e32
 │   ├── libutil.c32
 │   ├── menu.c32
 │   ├── pxelinux.cfg -> ../pxelinux.cfg
 │   └── syslinux.efi
 ├── efi64
 │   ├── CentOS-7-x86_64 -> ../CentOS-7-x86_64
 │   ├── ldlinux.e64
 │   ├── libutil.c32
 │   ├── menu.c32
 │   ├── pxelinux.cfg -> ../pxelinux.cfg
 │   └── syslinux.efi
 └─── pxelinux.cfg
     ├── default
     └── 00:11:22:33:44:55

We then need the DHCP server to pass the correct bootloader filename to the client. As per BIOS PXE booting, efi expects to use the filename DHCP option. Therefore we need to pass one of the following DHCP options depending on the type of client. This could either be done manually on a per client basis, or with a conditional on the vendor-class-identifier:

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if substring (option vendor-class-identifier, 15, 5) = "00000" {
  filename "bios/pxelinux.0";
} elsif substring (option vendor-class-identifier, 15, 5) = "00006" {
  filename "efi32/syslinux.efi";
} else {
  filename  "efi64/syslinux.efi";
}

Finally, you need to make sure your Linux install creates a suitable EFI partition. For anaconda installers using a kickstart file, it’s a simple as adding the following to your parition definition

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part /boot/efi --fstype vfat --size=200