On 02/02/2016 08:05 AM, Simon Hobson wrote:
> Exposing my ignorance here, what would need to write to the EFI stuff ? That article quotes someone as saying mounting it read-only would break some userspace stuff - so what would it break and why does it need to write there ?
> Not having actually dealt with EFI other than as a user, I don't recall stuff having to write to BIOS settings !
>

I'm not familiar with EFI, either, but these were mentioned as needing to
write to the EFI partition:
grub
efibootmgr
systemctl


Here's Poettering's last post on the github page -
https://github.com/systemd/systemd/issues/2402

"To make this very clear: we actually write to the EFI fs in systemd.
Specifically, when you issue "systemctl reboot --firmware" we'll set the
appropriate EFI variable, to ask for booting into the EFI firmware setup.
And because we need it writable we'll mount it writable for that."

Since I don't know what he's talking about, I checked the systemctl man
page, and here's what it says about the "firmware" argument to the reboot
command:

"If the optional argument arg is given, it will be passed as the
optional argument to the reboot(2) system call. The value is architecture
and firmware specific. As an example, "recovery" might be used to trigger
system recovery, and "fota" might be used to trigger a “firmware over the
air” update."

At least the paragraph above that does give a warning not to run
'systemctl reboot --force --force', which I suppose exists in case you
can't reach the power cord and really want to pull it.

I haven't seen anything mentioned that would require writing to the EFI
under ordinary circumstances.

fsr