[DO NOT MERGE YET] README: Booting from the external microSD card

[Velsoth]

Howdy.

I have recently acquired a Kobo Aura which does not have an internal microSD card, but instead a embedded BGA chip for storage.

After scouring the internet looking for documentation on how to boot from the external microSD I was able to get okreader running from it without any apparent issues.

This PR documents the most important steps I took in order to accomplish this and I would like some feedback on a few issues.

For instance, I do not know if the process through which one acquires a shell should be detailed in the README as most of the documentation and tools I came across didn't seem particularly trustworthy.

Is there a way to access a terminal emulator on Nikel? What is the recommended way to get an SSH or Telnet daemon on Nikel?

Additionally I came across some difficulties when booting from a formatted rootfs.

Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(179,9)

It seems likely that my mkfs.ext4 was including some options the ereader didn't like, or maybe I was doing something wrong, so for my installation I opted to purge all files from it instead of formatting. I believe this would affect anyone doing an internal microSD install as well.

Also, I have previously documented the cloning of the internal memory with netcat via telnet, but I believe its faster to do it directly.

Is anyone willing to try this out?

Thanks for your time and for maintaining okreader.

[klundry]

Hi, I've attempted to follow these instructions with my Aura and I'm not sure where I've gone wrong. When I attempt to boot from sd card I get a blank white screen and then have to hard power off to boot back to the stock internal firmware. I'm going to give it another shot starting from the beginning before I declare that it doesn't work.

I would like some clarification about the part where you use a hex editor. Do I need to edit the file with a hex editor and then also run this command "printf '\x01' | dd of=ereader.hwconfig bs=1 seek=63 count=1 conv=notrunc" after? I'm also not sure I correctly edited the file with the hex editor. I used hexcurse, hit Ctrl-g to goto 0x3F, hit the number 1 and saved.

[prokinkd]

@Velsoth
Hi. I was able to successfully install okreader on two Kobo Aura N514 devices following this guide.

I used https://github.com/S-trace/kobo-aura-remote to gain SSH access.
I had to use -oKexAlgorithms=+diffie-hellman-group1-sha1 option when connecting to the device from Ubuntu 18.04 over SSH, because, apparently, kobo-aura-remote provides outdated binaries.
Another caveat is that devices seemed to disconnect from Wi-Fi regardless of timeout settings. It caused SSH shell to freeze and not respond, but was not affecting the copy progress. Reconnecting to Wi-Fi, or switching Wi-Fi on/off restored SSH connecton.

I wasn't able to boot with freshly created ext4 partition too, it ended with boot led blinking abruption and blank white screen. Using first partition (rootfs) from dumped internal memory worked fine.
I applied couple of tweaks on it to reduce writes:
tune2fs -O ^has_journal /dev/<okreader-root-partition> -- disable journaling
tune2fs -E mount_opts=noatime /dev/<okreader-root-partition> -- disable file access time recording
e2fsck -f /dev/<okreader-root-partition> -- make sure that everything is OK

@klundry

I would like some clarification about the part where you use a hex editor. Do I need to edit the file with a hex editor and then also run this command "printf '\x01' | dd of=ereader.hwconfig bs=1 seek=63 count=1 conv=notrunc" after?

No, you don't need to do both. Running this command is enough, it does same as editing file with HEX editor.

When I attempt to boot from sd card I get a blank white screen and then have to hard power off to boot back to the stock internal firmware.

I had the same symptoms with fresh filesystem, but that also may be an issue with improperly edited hwconfig.

[klundry]

Thank you @prokinkd Will try this again soon. Appreciate the additional info on getting it to work.

[ergofroggy]

Thanks @Velsoth for this PR, and @prokinkd for the details on how to effectively ssh into the aura while still running Nickel.
Everything worked like a charm on my Aura, boots and works. Now to try and cross-compile okreader with a newer version of koreader