Grub2 tries to load filename with trailing dash character

sebbernard · May 25, 2018, 9:44am

We’re trying to provision a DL380G9 with a UEFI PXE Boot.

When creating a new machine for provisionning, grub.cfg is not loaded as expected.
The file grub.cfg-1- is correctly generated.

After a quick debug with tcpdump and debug log, I observed the firmware is trying to load a grub.cfg-- (note the trailing dash) file which is effectively not found.
Adding a trailing dash at the end of file fixes the problem.

boot loader is grub2/grubx64.efi from foreman-bootloaders.

I wonder if I didn’t do a mistake in the tftp setup. Where does this trailing dash come from ?

lzap · May 25, 2018, 8:32pm

It is a bug in grub2 (actually bug in Red Hat downstream patch). Two options:

A) Apply a workaround in grub2 config file which we ship in 1.17+ I think (you can easily edit the template):

github.com

theforeman/community-templates/blob/82e8d1bad20ab9bd770c26da9bc5f3ed3fbdcfa0/provisioning_templates/PXEGrub2/pxegrub2_global_default.erb#L11-L19


# On Debian/Ubuntu grub2 does not have patch for loading MAC-based configs. Also due to bug
# in RHEL 7.4 files are loaded with an extra ":" character at the end. This workarounds both
# cases, make sure "regexp.mod" file is present on the TFTP. For more info see:
# https://bugzilla.redhat.com/show_bug.cgi?id=1370642#c70
insmod regexp
regexp --set=1:m1 --set=2:m2 --set=3:m3 --set=4:m4 --set=5:m5 --set=6:m6 '^([0-9a-f]{1,2})\:([0-9a-f]{1,2})\:([0-9a-f]{1,2})\:([0-9a-f]{1,2})\:([0-9a-f]{1,2})\:([0-9a-f]{1,2})' "$net_default_mac"
mac=${m1}-${m2}-${m3}-${m4}-${m5}-${m6}
configfile=/grub2/grub.cfg-01-$mac
source "$configfile"

B) Update your OS to have fixed grub2 and redeploy grub2 onto TFTP (our installer creates a copy or calls grub2-mknet if I remember correctly so do that). If on RHEL that’d be 7.5:

https://bugzilla.redhat.com/show_bug.cgi?id=1483740

Broken grub2 is from RHEL 7.4.

sebbernard · May 26, 2018, 10:03pm

Thanks for the information.
I took the grubx64.efi from the version available in the foreman-bootloaders-redhat rpm package availble from the foreman yum repository.
I thought those provided were the prefered version to work with.
The package have to be updated with good known working version.

lzap · May 28, 2018, 6:53am

We stopped using this since in RHEL 7.4 grub2 is now shipped in noarch packages for all supported architectures. Just update the OS on smart-proxy, delete the EFI file and re-run the installer to regenerate it via grub-mknetdir.

I have updated the README to reflect this as I don’t plan keep extracting the bootloaders in the future. If anyone can takeover, that’d be appreciated because getting those might be tricky.