How do I resolve unmet dependencies?
I've a problem. Upgrade failed after "Setting new software channels", when Calculating changes. I tried error:
Not all updates can be installed An unresolvable problem occurred while calculating the upgrade: E:Unable to correct problems, you have held broken packages. This can be caused by: * Upgrading to a pre-release version of Ubuntu * Running the current pre-release version of Ubuntu * Unofficial software packages not provided by Ubuntu If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.
Now i have 1580 packages to update and do not update. Partial system upgrade also fails in the first step. What next? Alternatively, to undo the changes? Thank's to help.