Help booting to alternative partition on a GS1900-8HP

[BigAlly]

I had successfully installed OpenWrt 23.05.0 on one of my GS1900-8HPv2, but I am now just getting an index instead of a login page when accessing the switch over HTTP, the switch is still accessible via SSH.
Running /www/cgi-bin-luci via SSH returns "-ash: /www/cgi-bin-luci: not found". As this switch has dual firmware I would like to boot into the secondary partition which is still configured with the OEM firmware, however all the topics I seem to find have guides on carrying out the procedure from the initramfs, which have commands that are not available to me.
Can anyone help ?

[andyboeh]

See here:

ZyXEL GS1900 dual partitions - how to use it

In the original ZyXEL firmware, you can select which firmware to boot ("Active" or "Backup"). While OpenWrt can only be installed in the first partition, as already mentioned, you can trigger loading the OEM firmware from the second partition. It's as easy as running: fw_setsys bootpartition 1 That's the easiest method to return to stock. You can then overwrite OpenWrt with a stock firmware. You might need kmod-mtd-rw in order to be able to mount the config partition read/write. The first-…

[BigAlly]

I've tried running that command then 'reboot' but it still starts OpenWrt

[andyboeh]

Did you get any output or error message?

[BigAlly]

no, no errors

[andyboeh]

Is it possible that you accidentally flashed OpenWrt to the second image slot during installation? Once booted, couls you try running

fw_printsys

and tell us what the bootpartition points to?

[BigAlly]

running fw_printenv after 'fw_setsys bootpartition 1' shows bootpartition=1
rebooting and running fw_printenv then shows bootpartition=0

[andyboeh]

OK...it's also possible that you never flashed an OEM image to the second partition hence you cannot go back to stock this way. I don't know what other methods are there to flash back to stock, someone else will have to chime in here.

[BigAlly]

the OEM firmware was originally flashed to both partitions & fw_printsys shows
dualfname1=runtime-GS1900-8HPv2-V2.70(AAHI.5).bix
dualfname0=openwrt.bin

[p865976]

Did you ever get anywhere with this? Same boat here with OEM firmware on dualfname1, but can't get the switch to boot from it.

[BigAlly]

No, but have decided to have another crack at it
running 'fw_setsys bootpartition 1' then rebooting with a serial connection displays the following :-

Booting image from partition ... 1

Bad Header Checksum
ERROR: can't get kernel image!

Boot from partition 1 failed. Try to boot from partition 0

[BigAlly]

solution was simple,
Follow the guide for flashing the image using TFTP, but instead of uploading the openwrt.bin, upload the Zyxel provided .bix file instead.
Once complete, boot the image, log into the web page using the default Zyxel credentials

Checking the partitions via the WebGUI shows that the newly applied image shows as 'unknown', to resolve that, I then uploaded the same .bix file to the backup partition & restarted using that partition