Ok.... here's a stab at what we can put in this warning (maybe it can be in the main warning page with a sentence or two excerpted for the canned response.... feedback welcome.
The use of
opkg upgrade is very highly discouraged, and should be avoided in almost all circumstances. This is also distinctly different from the
sysupgrade path for upgrading both major versions and maintenance upgrades of OpenWrt -- the two are not equivalent.
Just because there is an updated version of a given package does not mean it should be installed or that it will function properly.
Unlike the 'big distros' of Linux, OpenWrt is optimized to run on systems with limited resources. This includes the opkg package manager, which does not have built-in ABI (Application Binary Interface) compatibility and kernel version dependencies verification. Although sometimes there may be no issues, there is no guarantee and the ugprade can result in various types of incompatibilities that can range from minor to severe, and it may be very difficult to troubleshoot. In addition, the opkg upgrade process will consume flash storage space and as it does not overwrite the original (stored in ROM), but stores it in the r/w overlay.
In the vast majority of cases, any security patches of significant importance/risk will be rapidly released in an official stable maintenance release to be upgraded using the sysupgrade system. This is the recommended method for keeping up-to-date.
Those looking to be on the bleeding edge can consider using the snapshot releases, but should be mindful of the differences between stable and snapshot. The remaining users who still want to use
opkg upgrade should only do so with individual packages (do not blindly update) and they should be aware that problems may occur that could necessitate a complete reset-to-defaults to resolve.
If you're already having issues, or wish to 'undo' the upgraded packages: create a backup (optional; can be restored after the reset is complete) and then perform a reset to defaults (