Syslinux - Jan 2017 - Possible to persist data across reboots from Lua?

I'd like to be able to save a boolean value across reboots. I believe
that being able to store to the auxiliary data vector would satisfy
this need, but I'm using syslinux and that doesn't seem to be
implemented. While I'm currently using a Lua script, I'm not tied to
it, so if there's a way to read and write any persistent filesystem or
disk, I'd be happy to switch. Reading through the source code, it
seems like most filesystem operations are read-only and I couldn't
find any information on the wiki. If this is possible, could you point
me to an example or where to read up?

Thanks,
Frank

Frank Hunleth via Syslinux <syslinux at zytor.com> writes:
> I'd like to be able to save a boolean value across reboots. I believe
> that being able to store to the auxiliary data vector would satisfy
> this need, but I'm using syslinux and that doesn't seem to be
> implemented.
It's implemented in the Syslinux API, just not exported to Lua.
> While I'm currently using a Lua script, I'm not tied to it, so if
> there's a way to read and write any persistent filesystem or disk,
I'd
> be happy to switch.
I think the best would be adding Lua bindings for syslinux_getadv(),
syslinux_setadv(), syslinux_adv_write(), syslinux_adv_size() and the
BOOTONCE and MENUSAVE tags.  And define some policy for allocating new
tags... which is the hard part.
> Reading through the source code, it seems like most filesystem
> operations are read-only
Yes, the filesystem drivers in Syslinux are read-only.
-- 
Feri

On Fri, Jan 27, 2017 at 7:54 AM, Ferenc W?gner <wferi at niif.hu>
wrote:
> Frank Hunleth via Syslinux <syslinux at zytor.com> writes:
>
>> I'd like to be able to save a boolean value across reboots. I
believe
>> that being able to store to the auxiliary data vector would satisfy
>> this need, but I'm using syslinux and that doesn't seem to be
>> implemented.
>
> It's implemented in the Syslinux API, just not exported to Lua.
>
>> While I'm currently using a Lua script, I'm not tied to it, so
if
>> there's a way to read and write any persistent filesystem or disk,
I'd
>> be happy to switch.
>
> I think the best would be adding Lua bindings for syslinux_getadv(),
> syslinux_setadv(), syslinux_adv_write(), syslinux_adv_size() and the
> BOOTONCE and MENUSAVE tags.  And define some policy for allocating new
> tags... which is the hard part.
Thanks. That points me in the right direction for where to look.

Frank
>
>> Reading through the source code, it seems like most filesystem
>> operations are read-only
>
> Yes, the filesystem drivers in Syslinux are read-only.
> --
> Feri


-- 
Frank Hunleth
Troodon Software LLC
Embedded Software Development
http://troodon-software.com/