[yocto] [rauc] create a rescue image

[Mike Looijmans]

On 26-03-19 11:02, jairo wrote:
> El mar, 26-03-2019 a las 09:14 +0100, Patrick Boettcher escribió:
>> On Tue, 26 Mar 2019 09:05:47 +0100
>> jairo <jairo at futurasmus-knxlab.es> wrote:
...
> Yes, I know, it is somewhat risky, but I have only 512MB of nand
> memory, and we are getting a lot of software. I think we have to
> evaluate the move to a hardware with more memory, at the moment is what
> we have. I think it is practically impossible to put 2 systems in so
> little memory.

With NAND you'll probably have a filesystem (jffs2 or UBI) in place. With 
that, you could just use a package manager like opkg to update sofware. If the 
box has a network connection, just running "opkg update && opkg upgrade" will 
install the current releases with the minimum effort. We've been using this on 
a million boxes and it works fine (until someone decides to patch libc and you 
get a 300+ package upgrade).

Linux is also capable of upgrading a running system. Basically, copy some 
executables to a tmp filesystem, remount everything read-only, and change root 
to the tmp part. Then you can rewrite partitions and reboot.

In any case, you should have a u-boot configuration that allows it to be 
debricked. Typically a USB stick or DFU will do nicely if your board has USB. 
Or even serial...