[syslinux] Getting HTTP path-prefix to work with syslinux.efi

[Alexander Perlis]

 >> None of Dell OptiPlex 990 (firmware A19), 9010 (firmware A22),
 >> nor 9020 (firmware A16) seem have a built-in EFI shell option,
 >> but in all three cases I had success running the external EFI
 >> shell from github.com/tianocore/edk2/tree/master/EdkShellBinPkg
 >> (naming it /efi/boot/bootx64.efi on a FAT USB stick).
 >
 > Examining a 9020 I have access to, I'm guessing that depends on what's
 > on the HDD.

Ah yes, I suppose my original HDD contents (long gone) might have had a 
shell EFI on it.


 >> What does it mean for TCPv4Sb to be listed under "guid" yet not
 >> under "dh -p Net"? Curiously, on the OptiPlex 990, the "dh -p Net"
 >> output is bizarrely essentially empty:
 >
 > It means it understands what alias to assign for the GUID but might
 > not have a binding for it or placed it elsewhere.  The following would
 > find the binding if it existed elsewhere.
 >
 > dh -p TCPv4Sb

Unfortunately for me the binding doesn't exist elsewhere. Output below.


Dell OptiPlex 990 A19 (EFI 2.0 Revision 4.632 American Megatrends):

Shell> dh -p Net
Handle dump by protocol 'Net'

Shell> dh -p TCPv4Sb
Handle dump by protocol 'TCPv4Sb'



Dell OptiPlex 9010 A22 (EFI 2.31 Revision 4.653 American Megatrends):

Shell> dh -p Net
Handle dump by protocol 'Net'

   326: DevPath (..9,0x0)/MAC(xxxxxxxxxxxx,0x0))Net MNPSb ARPSb DHCPv4Sb
IPv4Sb IPv4Config UDPv4Sb MTFTPv4Sb HiiConfAccess

Shell> dh -p TCPv4Sb
Handle dump by protocol 'TCPv4Sb'



Dell OptiPlex 9020 A16 (EFI 2.31 Revision 4.653 American Megatrends):

Shell> dh -p Net
Handle dump by protocol 'Net'

   335: DevPath (..9,0x0)/MAC(xxxxxxxxxxxx,0x0))Net MNPSb ARPSb DHCPv4Sb
TCPv4Sb IPv4Sb IPv4Config UDPv4Sb MTFTPv4Sb HiiConfAccess

Shell> dh -p TCPv4Sb
Handle dump by protocol 'TCPv4Sb'

   32F: DevPath (..9,0x0)/MAC(xxxxxxxxxxxx,0x0))Net MNPSb ARPSb DHCPv4Sb 
TCPv4Sb IPv4Sb IPv4Config UDPv4Sb MTFTPv4Sb HiiConfAccess



 > The observed behavior is inline with my
 > expectations for this output.

I appreciate having now learned about EFI shells and how to dig deeper 
to an explanation of the behavior.

Alas, it looks like I'll have to keep my 990 and 9010 in BIOS mode, and 
start using EFI with the 9020 and newer, at least until I have a chance 
to try something like the ipxe snponly that you suggested.

My actual motivation pursuing EFI is to ultimately get newer Macs to EFI 
pxe boot to our pxe server menu (which we use for media installation), 
since for Macs we don't have the BIOS alternative. I just wanted to 
first tackle our Dell EFI systems before chewing on the Mac EFI.

Thanks,
Alex