[CentOS] wiki howto on custom kernel
Alfred von Campe
alfred at 110.net
Mon Mar 12 19:53:50 UTC 2007
On Mar 12, 2007, at 10:15, Jim Perrin wrote:
>> 3. After copying the config file an making one small
>> change with "make xconfig", why are there so many
>> differences in the config file?
>
> Are they actual changes, or is the diff now simply off by a few lines?
I went back and started the process of building a kernel from scratch
on a different system. This time I paid closer attention to what was
going on. After the "rpmbuild -bp --target=`uname -m`
kernel-2.6.spec" step, the ~/rpmbuild/BUILD/kernel-2.6.9/linux-2.6.9
directory contains among other things these two files:
-rw-r--r-- 1 rpmbuild rpmbuild 50332 Mar 12 15:32 .config
-rw-r--r-- 1 rpmbuild rpmbuild 61600 Mar 12 15:31 .config.old
Notice the size difference of these two files. After copying the
config file from the ~/rpmbuild/SOURCES directory, these two files
now look like this:
-rw-rw-r-- 1 rpmbuild rpmbuild 61600 Mar 12 15:42 .config
-rw-r--r-- 1 rpmbuild rpmbuild 61600 Mar 12 15:35 .config.old
And a diff confirms the the two files are now identical. However,
after doing a "make xconfig", changing two settings in the Serial
Port section and saving the config file, the directory looks like this:
-rw-rw-r-- 1 rpmbuild rpmbuild 50322 Mar 12 15:44 .config
-rw-rw-r-- 1 rpmbuild rpmbuild 61600 Mar 12 15:42 .config.old
Finally, comparing the new .config file with the original .config
file only shows the expected changes:
# diff /tmp/saved_configs/.config .config
4c4
< # Mon Mar 12 15:32:01 2007
---
> # Mon Mar 12 15:44:32 2007
1501c1501
< CONFIG_SERIAL_8250_NR_UARTS=4
---
> CONFIG_SERIAL_8250_NR_UARTS=16
1503c1503
< # CONFIG_SERIAL_8250_MANY_PORTS is not set
---
> CONFIG_SERIAL_8250_MANY_PORTS=y
While I don't quite understand what is going on, it appears that
xconfig is doing the right thing. I'm rebuilding the kernel again as
I type this. BTW, there are lots of compiler warnings: is this
normal/expected for a kernel build?
Alfred
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