How to tell if kernel compiled from kernel.org is x86_64 or just 32 bit?

[Sharpe, Sam J]

2009/6/21 Antonio Olivares <olivares14031 at yahoo.com>

>
> Dear fellow Fedora users,
>
> Is there a way to tell if a kernel is 64 bit or 32 bit? If one compiles and
> installs a kernel from kernel.org.  Why am I asking?  I have a 64 bit
> Fedora 11 installed and it showed 2.6.29.4-???x86_64 at the end so I know it
> is a 64 bit kernel.  I copy the config of that kernel and compile a new one
> and install it, is that kernel still a 64 bit kernel or is it a 32 bit
> kernel?  When compiling I see just x86/ directories in the source of the
> kernel and no x86_64?
>
> I have a modem that needs drivers to con nect the modem is 32 bit only but
> can be compiled in 64 bit code, I tried without success compiling it against
> the 2.6.29.4-?? x86_64 kernel.  However, after compiling the kernel from
> kernel.org and compiling the same code it succeeded and it runs under the
> 2.6.30 kernel.  I know that `uname -a` will tell many things about our
> running kernels, but is there something else that can tell us?
>
> Or when we compile a kernel.org kernel, do we have to say compile it in 64
> bit?
> I have compiled several kernels, but not knowing if the new kernel is
> indeed 64 bit or not?
>

The config file for the kernel which should be .config in the directory
where you built the kernel will tell you. Fedora kernels copy this file to
an appropriately named one in /boot.

Thus:

[sam at samlap boot]$ grep CONFIG_X86_64 config-2.6.29.4-167.fc11.x86_64
CONFIG_X86_64=y
CONFIG_X86_64_SMP=y
CONFIG_X86_64_ACPI_NUMA=y

This is a 64bit kernel...


-- 
Sam
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