# Is the .config of 64bit same as that of 32bit linux?

## clouds222

I'm just wondering to migrate my gentoo to 64bit version.. But I want to confirm if the current .config can be used to build new kernel.

----------

## aCOSwt

Do not do that.

Several settings, at least within the Processor type and features section differ from x86 to x86_64

----------

## clouds222

Oh, yes, but I think there is not so much difference besides datawidth? Only CPU?

or I shall compare the 64bit .config with 32bit, and make some changes.  I didn't edit the config line by line, but a friend did.

----------

## Gusar

You can start with the current .config. But definitely run 'make menuconfig' or 'make k/gconfig' on it and go through all the options, making sure everything is set as you want/need it to be.

----------

## aCOSwt

Well... you get differences in Power Management and Bus Options sections too... so... really... I do insist in discouraging such an initiative.

I would definitely personally make menuconfig from scratch.

If you do not want / get no time for caring with this, then taking some ready-made .config from pappy's kernel seeds or going with genkernel would imho even be better than taking back your x86 .config as is.

----------

## clouds222

Oh, my current .config is tweaked by pappy, it works very stable and fast, so I think it's just the right configuration for my computer. That's why I have the question.

----------

## d2_racing

Indeed, the 64 bits .config has a lot more options.

----------

## Hu

At the price of some extra time, you could do a reasonably safe 64-bit configuration by opening one menuconfig for the new 64-bit kernel and a separate menuconfig on the existing 32-bit kernel.  Use what is shown in the 32-bit configuration to guide your selections in the 64-bit one.  This will provide a clean 64-bit kernel, but also give a good chance of retaining as many of the desired features as possible.

Note that this will only switch you to a 64-bit kernel.  Switching to a 64-bit user profile in place is not supported.  However, once you have a 64-bit kernel, you can run your existing 32-bit user profile via IA32 emulation, and maintain a chroot where you install a new 64-bit system.  You can then cut over to the new system once you are happy with it.  This does require having adequate space to have two copies of Gentoo, at least temporarily.

----------

## clouds222

OK, Thank you all, so I'll carefully configure the kernel for my 64bit gentoo. and Now, I'll first back up some important files in my system.

----------

## d2_racing

You can use a Stage 5 backup or even Rsync if you want.

----------

