Default Kernel .config file

Rick Stevens rstevens at vitalstream.com
Fri Jun 16 23:00:45 UTC 2006 

On Fri, 2006-06-16 at 08:31 -0500, Harrington, Todd wrote:
> 
> -----Original Message-----
> From: Harrington, Todd 
> Sent: Friday, June 16, 2006 9:10 AM
> To: 'Getting started with Red Hat Linux'
> Subject: RE: Default Kernel .config file
> 
> 
> 
> Hi Rick,
> 
> Thanks for your answer. It was very helpful and answered 
> several smaller questions I had. I have built my new kernel,
> modules, modules_install, install. I then copied the /boot 
> and the /lib directory back over to my boot server. 
> I did not re-run mkinitrd because when I run the RHEL4 
> Network Booting Service (system-config-netboot) it asks me to 
> point to a kernel and I point to 
> /diskless/i386/RHEL4-ES/root/ (where it finds the new kernel 
> that I just installed) and it then builds an 
> initrd.img for me and sticks the initrd.img and new kernel
> into /tftpboot/linux-install/IMAGENAME
> There sizes look very good.
> 
> So my problem NOW is that when my diskless client boots the 
> kernel loads and then I get this from initrd:
> 
> RAMDISK: Compress image found at block 0
> -
> -
> Running /disklessrc
> Mounting /proc
> disklessrc: Line 71: /sbin/uniq: Permission denied
> disklessrc: Line 66: /sbin/sed: Permission denied
> disklessrc: Line 68: /sbin/uname: Permission denied
> disklessrc: Line 68: /sbin/grep: Permission denied
> (several more lines of this)
> Loaded nfs OK
> Mounting /
> disklessrc: line 163: /bin/cat: Permission denied
> Running dhclient
> bash-3.00#
> 
> At this shell all commands are permission denied.
> 
> This is so important that I get by this today.
> Do you know what my problem is? 
> 
> Thanks,
> Todd
> 
> -----Original Message-----
> From: redhat-install-list-bounces at redhat.com
> [mailto:redhat-install-list-bounces at redhat.com]On Behalf Of Rick Stevens
> Sent: Thursday, June 15, 2006 4:51 PM
> To: Getting started with Red Hat Linux
> Subject: Re: Default Kernel .config file
> 
> 
> On Thu, 2006-06-15 at 15:08 -0500, Harrington, Todd wrote:
> > Hello,
> > 
> > I am installing RHEL4 ES on a "client" computer. I do a fresh load to a local hard drive on the "client" with the goal of eventually making this node a "diskless client" that will boot via PXE.. 
> > I use the Netboot GUI on my Linux "server" (another machine) that comes with RedHat and it pulls the image and kernel from my hard drive on my "client" and I can now PXE boot my client from the server. I am actually now booting the default kernel that was installed on the hard drive of my "client". Life is good. 
> > 
> > My problem is that I want to reconfigure the kernel on my client and when I do, the default .config files (in the "configs" directory or the Config-xxx file in the /boot directory) do not contain the same settings as are in my original kernel and my new kernel does not boot across the network. I have been pulling my hair out trying to get my new kernel to boot. How can I get the default .config settings for the kernel that was initially installed to my local hard drive? I read about "extract_ikconfig" and /proc/config that allow you to pull the .config info from a kernel but you have to have that support in the kernel in the first place. It does not appear the initial RedHat install included this in the kernel.
> 
> In the future, please format your messages as plain text, 72 characters
> per line.  Not all mail readers deal with long lines well.
> 
> Now, to your problem...
> 
> When RHEL installs, the config file that matches the kernel that was
> installed is the "/boot/config-`uname -r`" file.  The only difference
> between that config file and the actual kernel is that the kernel was
> built with the "CONFIG_DEBUG_INFO" option (in the "Kernel->Hacking"
> section) turned off, which creates modules that don't have full debug
> info in them and are therefore smaller in size.
> 
> Also note that the default kernels put all of the network, SCSI and
> non-ext2 filesystem drivers in the initrd image file.  If you
> reconfigure the kernel, you have to rebuild the initrd image.  That's
> done by:
> 
> 	# cd /boot
> 	# mkinitrd -f -v initrd-whatever.img whatever
> 
> replacing "whatever" with the kernel version number you're working with.
> Note that both the kernel AND the initrd image must be on your boot
> server or the kernel won't be able to find the drivers it needs.
> 
> Now, you CAN reconfigure the kernel and build the necessary network
> and filesystem drivers into the kernel and remove the need for an initrd
> image completely, but if you change the hardware (say, swap out an
> Intel e1000 card for an Intel e100 card), you won't be able to boot from
> the network again since the driver for the card won't be present.
> 
> My quicky document on building kernels and such can be found here:
> 
> 	http://www.rhil.net/docs/kernelbuild-26.html
> 
> ----------------------------------------------------------------------
> - Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
> - VitalStream, Inc.                       http://www.vitalstream.com -
> -                                                                    -
> -               The Theory of Rapitivity: E=MC Hammer                -
> -                                  -- Glenn Marcus (via TopFive.com) -
> ----------------------------------------------------------------------
> 
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> 
> Hi, I am all set now. I was required to copy the file busybox.anaconda 
> to my client's /sbin directory and when I did the permissions did not 
> have execute permissions on it. I did a chmod to busybox.anaconda and now
> I can boot! Thank you to this mailing list.

Glad you got it sorted out, Todd.  And that's why the list exists!  :-)

----------------------------------------------------------------------
- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-   I haven't lost my mind.  It's backed up on tape somewhere, but   -
-                       probably not recoverable.                    -
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