[FS#826] Better implementation of upgrade system on lede

[LEDE Bugs]

The following task has a new comment added:

FS#826 - Better implementation of upgrade system on lede
User who did this - piotr (pietia)

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Hi,
@diizzyy 
How do we upgrade using web interface then? 
it's basically wget .zip 
optional (keep settings)
flash new zip 

So basically what we need to do using opkg upgrade is : wget proper latest zip for the device(check if your router uses latest stable version), 
sha256sum file (if sum matches proceed with flashing),
sysupgrade -v /tmp/filename-of-downloaded-sysupgrade.bin (this ensures that our config are saved),

That's in my opinion the easiest way to add this feature.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=826#comment2741