Install Yocto image and backup


JH
 

Apology if it is an off topic, I could not find proper mailing lists
to ask questions.

I built Yocto Linux kernel and installed Yocto image to MTD NAND
storage in an iMAX6 device, because we designed RO for the kernel and
root file system, RW for applications, we can update applications OTA
but we cannot update kernel and root file system OTA. My supervisor
asked if we need to have a dual NAND storage to backup the kernel and
root file image, if the NAND bad sector occurred in the primary image,
it can be booted from the secondary backup image. I understand where
the concerns come from, but I am not clear if it is necessary or if it
is a common practice to perform NAND backup storage, appreciate your
insight advice.

Thank you very much.

Kind regards,

- jupiter


JH
 

Hi Alexander,

Thanks for your advice.

In my opinion two things are common practice:

1) Using a layer on top of raw NAND, like UBI/UBIFS nowadays, so bad blocks
can be handled properly in a layer below your rootfs.
Yes, the UBI/UBIFS is used in NAND partitions, I guess you alluded
there is no need use the backup, right?

2) Using an A/B scheme for updating and using a well tested framework for
that (instead of self written shell scripts). You don't need another NAND chip
for that, just multiple partitions. You can still have your kernel/rootfs read-only at runtime.
If I do need to use a backup, it won't need another NAND chip, it will
be another UBI/UBIFS partition. But I would like as simple as possible
if no backup is a common practice.

Thank you very much.

Kind regards,

- jupiter


Matthias Schoepfer
 

Hi!

On 11/2/20 10:16 AM, JH wrote:
If I do need to use a backup, it won't need another NAND chip, it will
be another UBI/UBIFS partition. But I would like as simple as possible
if no backup is a common practice.
The A/B partitioning is very common and I would argue, it is the simplest way if you want you OTA Update to be safe in regards of any errors (user unplugging etc.) that may happen during write / switching to new software. If you can spare the extra partitions on your NAND, my advice would be to do it exactly that way, and use a common tool for that (i.e. swupate, rauc, ... ).

Regards,

  Matthias


JH
 

Thanks Matthias,

The A/B partitioning is very common and I would argue, it is the
simplest way if you want you OTA Update to be safe in regards of any
errors (user unplugging etc.) that may happen during write / switching
to new software. If you can spare the extra partitions on your NAND, my
advice would be to do it exactly that way, and use a common tool for
that (i.e. swupate, rauc, ... ).
We don't have OTA update for RO kernel and rootfs yet, I'll take the
advice for running OTA A/B partitioning when the requirement is
coming.

Thank you all for your kind responses.

Kind regards,

- jupiter


JH
 

Hi Alexander,

Thanks for your clarification.

If your kernel and rootfs partition is just one UBIFS in a bigger UBI volume,
then no. Single bad blocks affecting the UBIFS partitions would be handled
by the underlying UBI. You should however consider using ubihealthd or
something similar to become aware of badblocks over time and handle them before it's
too late and you can not boot from the rootfs anymore, especially if it is read only and not
touched for writing in normal operation.
Yes, I use one UBIFS for 4 partitions, RO rootfs, RO kernel, RO DTB
and RW application, no write for RO partitions, that should be safe, I
feel relieved.

your device is somehow connected to a network. So what I suggested was having
two rootfs partitions. One is active and the device boots from it (A), and the
other one acts as inactive (B). When you update, write the new rootfs to the
inactive partition and then just switch over and boot B instead. You might add
a third partition for recovery or factory reset. Only the active partition
would be used in the running system and can still be readonly there.
The reason we don't update kernel and rootfs because the size of
kernel and rootfs is too large, it is hard to download 60MB image OTA
via 4G CAT M1. If we are going to change to use 4G CAT1 or higher
speed, I'll use either RAUC or SWUpdate, which one is the most popular
for embedded system using uboot and UBFIS?

Thank you very much.

Kind regards,

- jupiter


Richard Weinberger
 

On Tue, Nov 3, 2020 at 10:17 AM JH <jupiter.hce@...> wrote:
The reason we don't update kernel and rootfs because the size of
kernel and rootfs is too large, it is hard to download 60MB image OTA
via 4G CAT M1. If we are going to change to use 4G CAT1 or higher
speed, I'll use either RAUC or SWUpdate, which one is the most popular
for embedded system using uboot and UBFIS?
You don't need a full download.
In the past I've used binary diffs with great success.

So if the update size is your biggest concern, the tradeoff of
computing and applying
the binary diff might be worth it.

--
Thanks,
//richard