I'm reading the above and it says that you can verify checksums against the web page where you got your image. But this is to verify that it is a legitimate openwrt or other image I believe.
However, when building my own image, I know where it comes from so the only thing I want to make sure of is that the image was not broken during download before I sysupgrade? That is what I cannot seem to find information on.
That said, if I recall, sysupgrade itself checks the image to make sure it is complete otherwise it fails right?
You want to verify the integrity of the image before you flash it. This means that it has not been altered from its original location, either the download server of OpenWrt or your hard drive. This verifies that there was no error during transmission. If you flash from Luci it will be calculated after you upload the file. Better use sha256, it is the current standard.
Don't rely on sysupgrade itself to check the image. I have seen posts in here from users who accidentally flashed the wrong image
I tried to explain but I don't think I did a good job :).
There is no luci stuff, just command line.
I am not caring where the image comes from since it is my own build.
What I want is to make sure that is it complete, did not get trashed in some way transferring it to the router before using sysupgrade.
By integrity, I mean it's own completeness so that it is safe to write to the router. I'm not going to flash the wrong image, I just want to make sure the image is ok to flash first.
I added that I think I recall sysupgrade complaining when the image was either corrupted or not for the right arch.
Don't rely on sysupgrade itself to check the image. I have seen posts in here from users >who accidentally flashed the wrong image
This says a lot then :).
So, the answer is to generate a checksum code when building.
Yes, it's the answer that has been mentioned and sounds like the solution. I just need to find some information on how to generate the MD5 when using image builder so I can use it on the router to confirm the image integrity.