Refer to https://tech.wandersick.com/2016/06/scripted-boot-to-windows-pe-using-hp.html

winpe_boot_ilo_uefi.ps1

# Version: 1.0
# Last Update: 20 Oct 2015
# iLO Cmdlet Version (at the time): 1.2
# Author: wandersick (http://tech.wandersick.com)

$iloIP = "HP_iLO_IP_addr"
$iloUserName="administrator"
$iloPassword="********"
$isoUrl ="http://web_srv_IP_addr/winpe.iso"

# Mount Windows PE iso
Mount-HPiLOVirtualMedia -Server $iloIP -user $iloUserName -pass $iloPassword -Device CDROM -ImageURL $isoUrl

# Connect the virtual media on next boot (change BOOT_ONCE to CONNECT to connect the media now and leave it mounted even after the next boot)

Set-HPiLOVMStatus -Server $iloIP -user $iloUserName -pass $iloPassword -Device CDROM -VMBootOption BOOT_ONCE

# Verify the above commands by PowerShell (This is equivalent to shell command "vm cdrom get")
# Get-HPiLOVMStatus -Server $iloIP -user $iloUserName -pass $iloPassword -Device CDROM
# Where BOOT_OPTION: BOOT_ONCE and IMAGE_URL: http://....iso

# As boot order cannot be modified during POST, instead of setting boot order and reboot the server with ‘Reset’ (i.e. Reset-HPiLOServer -Server $iloIP -user $iloUserName -pass $iloPassword), this script attempts to perform a power-off of the HOLD type, set boot order and then power it back on to continue booting.

# Power OFF the server (Force)

Set-HPiLOVirtualPowerButton -Server $iloIP -user $iloUserName -pass $iloPassword -PressType HOLD

# UEFI - Boot from ISO URL on next boot (This is not the preferred method. See Persistent Boot method below.)

# BootCustom = UEFI Target

# Boot0008 = Generic USB Device (iLO attempts booting from all possible USB devices)
# Set-HPiLOOneTimeBootOrder -Server $iloIP -user $iloUserName -pass $iloPassword -Device BootCustom -BootCustomName Boot0008

# UEFI - Persistent Boot (Preferred)

Set-HPiLOPersistentBootOrder -Server $iloIP -user $iloUserName -pass $iloPassword -BootOrder Boot0008

# Power ON the server

Set-HPiLOHostPower -Server $iloIP -user $iloUserName -pass $iloPassword -HostPower "Yes"