New subject: [Bug 891467] Need a section in the install guide regarding pxe booting on UEFI systems

Wednesday, 2 January 2013

Product: Fedora Documentation
https://bugzilla.redhat.com/show_bug.cgi?id=891467

            Bug ID: 891467
           Summary: Need a section in the install guide regarding pxe
                    booting on UEFI systems
           Product: Fedora Documentation
           Version: devel
         Component: uefi-secure-boot-guide
          Severity: unspecified
          Priority: unspecified
          Reporter: jreed(a)redhat.com
        Depends On: 871565

+++ This bug was initially created as a clone of Bug #871565 +++

Description of problem:
Fedora 18 will see greater use of UEFI systems, and as such we should round out
our documentation regarding how to boot UEFI systems via other common methods
besides those already addressed.  Most notably the use of pxe boot in UEFI
environments will now be available with secure boot enabled via both ipv4 and
ipv6 the by using shim layer code:
https://github.com/mjg59/shim

We should further document how to boot a system and setup a pxe server to allow
booting UEFI systems in this manner

--- Additional comment from Jack Reed on 2012-11-12 01:01:52 EST ---

Thanks Neil.

Are you able to give me some details on how the procedure for setting up a PXE
server for EFI would need to be changed to account for this?

http://docs.fedoraproject.org/en-US/Fedora/17/html/Installation_Guide/s1-...

And I expect the "Booting from the Network using PXE" section needs to be
tweaked to account for EFI as well:

http://docs.fedoraproject.org/en-US/Fedora/17/html/Installation_Guide/sn-...

Are you able to tell me how this process differs on EFI systems? 

And what else would you like included here or elsewhere, particularly with
regard to secure boot being enabled via via both ipv4 and ipv6 the by using
shim layer code? I'm unclear on how this affects the procedure/s.

And what are the other common methods that are not addressed that you would
like to see covered?

--- Additional comment from Neil Horman on 2012-12-18 11:19:16 EST ---

Jack
I'm sorry, the description above isn't complete.  The additional need for
documentation here is not exclusively to support UEFI systems, but to support
them using PXE for IPV4 and IPV6 using non secureboot and secureboot
environments.  The documentation you have covers IPV4 in a non-secureboot
environment.  I'll try to touch on the general changes that need to be made in
each case:

PXE+UEFI+IPV4+NO Secureboot - You're good to go, no changes need to be made

PXE+UEFI+IPV6+No Secureboot - the server dhcp6 option is not filename, you need
to instead specify bootfile-url option, which is a text string of the form:
bootfile-url="tftp://[ipv6-address-in-brackets]/path/to/grub.efi

PXE+UEFI+[IPv4|IPV6]+Secureboot - You can't boot grub directly with secureboot
enabled, as its unsigned.  We're in the process of getting the shim utility:
https://github.com/mjg59/shim
It will be signed and needs to be specified as the filename option or the
bootfile-url option on the dhcp server.  The shim utility will be downloaded,
validated, and then it will be responsible for downloading the actual grub
image (which must be named grub.efi or grubx64.efi and be tftp-able from the
same location that the shim image was located at)

So, I'm not sure at how you're looking to organize the docs for fedora (if you
want to document secureboot booting procedures separately from non-secureboot
environments or not), but thats the information that I was hoping to cover in
this bz.  If you feel like you have all that information in various locations,
and can ennumerate them here, I think that would satisfy this bz in my mind. 
If any of it is missing however, and can be added, I would greatly appreciate
it.  I've got some virtual qemu guests setup to run an IPv6+UEFI+secure boot
emulated environment here which you're welcome to poke around with to help
flesh out the instructions if need be.  And of course, I'm happy to answer any
further quesstions you might have here.

Thanks!
Neil

--- Additional comment from Jack Reed on 2012-12-19 00:31:51 EST ---

Thanks for this, Neil. Having the distinct requirements for each use case
outlined is really useful.

However, I'm still not clear on the context or exact format of these
configuration changes. Are they made in /etc/dhcp/dhcpd.conf, a sample of which
is provided in step 4 of the following?

http://docs.fedoraproject.org/en-US/Fedora/17/html/Installation_Guide/s1-...

If so, I assume that 'filename "pxelinux/bootia32.efi";' should be
replaced
with 'bootfile-url="tftp://[ipv6-address-in-brackets]/path/to/grub.efi' (in
the
second use case you outline) or whatever is required for the third use case. Is
that correct?

But the config file in step 4 is only an example, and the filename strings in
it are relevant in case certain conditions are met, whereas the filename and
bootname-url strings you're referring to are perhaps uniform rather than
conditional.

Would you mind providing quick edited versions of that sample config file that
incorporate these IPv6 and IPv4/6 Secureboot strings? (I'm particularly unclear
on how to configure the latter.) Assuming that's where the editing needs to be
done, of course.

If it is, then explaining what is needed for IPv6 and SecureBoot in the
'Configuring for EFI' procedure may be enough, as opposed to breaking them off
into another procedure. If the steps prove too difficult to integrate though, I
will break them off.

That said, you might be interested in an F18 draft document I've just been
reminded of:
http://docs.fedoraproject.org/en-US/Fedora_Draft_Documentation/0.1/html-s...

It's only in the early stages, but the material you want to add may also be
beneficial here. Or you may feel that it is best suited to that guide alone. I
don't have the perspective on the applicability of this new material to gauge
that, so let me know what you think.

--- Additional comment from Neil Horman on 2012-12-19 09:11:43 EST ---

Sure, I'll attach my sample configs in a bit.

To answer your specific questions above:

1) When configuring pxe for IPv6 vs. IPv4, the dhcp server configuration needs
to change.  Specifially, when using ipv4 you need to specify the filename dhcp
option, exactly as it appears in the current netboot document you reference
above

When configuring pxe for ipv6 (weather or not you use secure boot, or UEFI for
that matter), in addition to modifying the dhcp server configuration to serve
ipv6 addresses, pxe support requires that you, instead of using the filename
dhcp option to specify the file to download, you instead use the bootfile-url
option, which is formatted as I noted above (its also expanded on in the
dhcp-options man page).

Note this change is orthogonal to any changes required to enable secureboot
over pxe.  This is just the change needed to support ipv6 pxe boot.  As you not
above, your configuration example is just that, an example.  I don't know if
you want to expand on it to demonstrate how pxe works differently with ipv6. 
If you do however (and I think it would be a good idea), the bootfile-url
option is what you need to document.

2) Secureboot, when enabling secureboot, you have to make some additional
changes.  Specifically you have to specify a special file to download (not just
the grub bootloader).  This is because grub won't be signed with the master
key.  The shim utility I mentioned before will.  If you're trying to boot a
system via pxe in UEFI secure boot mode using ipv4, you have to use the
filename dhcp option to specify that the shim utilty file be downloaded,
whereas if you are booting a system via pxe in UEFI secure boot mode over ipv6,
then you need to specify the shim utilty file on the dhcp server using the
bootfile-url option.  Note that if you are _not_ in secure boot mode, then you
can specify any pxe boot file that you want on the server.  Thats the meat of
the change here: When in secure boot mode you need to specify the shim utilty
as the file to download via tftp, as opposed to operating in non-secure-boot
mode, when you can download and run any arbitrary file.

Looking at your Secure boot page, I think thats a good start.  Perhaps thats
how this documentation should be split up - item (1) above can be edited into
the netboot documentation, to show how the dhcp server config changes when
using ipv6, and item (2) can be discussed in the secure boot page (since the
shim utiltiy is requried when using secure boot, regardless of weather your
booting locally or via pxe).

I'll attach my sample dhcpd6.conf file in just a moment.

--- Additional comment from Neil Horman on 2012-12-19 09:49:06 EST ---

Created attachment 666108
sample dhcpd6.conf file

Heres my example dhcpd6.conf file, which uses the bootfile-url option.  Note
that it specifies the shim.efi utility.  This setup was used to boot a system
in secure boot mode. If we weren't in secure boot mode, we could download any
file we wanted.  As it is, the shim utility is signed, alowing it to be run in
secure boot mode.  Once its validated, it will attempt to download the
grubx[32|64].efi file from the same location it was downloaded from.

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[Bug 891467] New: Need a section in the install guide regarding pxe booting on UEFI systems