After making careful and explicitly-named backups of every config-file you've ever used ... as a matter of standard practice
... you should run the
make menuconfig process of 2.6 (or whatever-it-is that you use) so that it has a chance to insert any newly-introduced option keys into it. Then review the settings again carefully. The kernel documentation is quite explicit about whatever has changed between the two versions, but they don't try to "maintain backward compatibility" between apples and oranges: the two kernels
are different, maybe in key ways, and the decisions to be made are
yours. The configuration scripts do, "run upgrades" once, but it's not a computer's job to be smart and they're terrible at being so.
---
Just to clarify,
every time I reconfigure a kernel, I always follow these steps:
- Copy the (hidden) config-file to a clearly-named (with date and time), non-hidden file in a chosen subdirectory, say, of /root. Write-protect that file. Copy it to a thumb drive you can find later.
- Rename the file to an alternate name.
- make distclean
- Rename it back (since the preceding step would have destroyed the old name).
- make ... etc.
These steps, which are designed to be repeatable, also ensure that the
entire kernel and all modules are cleanly rebuilt each time. I like procedures which I can repeat easily and without thinking about them, which minimize "surprises" of any sort. I don't
like surprises ...
