Can i 'patch' the kernel?

tntcoder · 05-23-2006, 06:38 AM

Hi,

I need to enable up to 4gb ram support in slackware 10.2, i already have the 2.6kernel installed, but its only detected 1gb of my 2gb ram, i would also like to enable dual core support if it is not running already.

Is there anyway i can mod this into the current kernel without going through the hasle of compling a new one from scratch?

Thanks
Jack

prozac · 05-23-2006, 07:01 AM

i don't think you need to start from scratch. just use your old config and make ammendments to your kernel.

Alien Bob · 05-23-2006, 01:30 PM

I wrote a short Wiki page on compiling a 2.6 kernel here: http://alien.slackbook.org/dokuwiki/...kernelbuilding - and mention enabling the 4GB option, too.

You need to recompile your kernel, but as prozac already said, it can be kickstarted by using the Slackware kernel .config file, so that all defaults are already set when you run "make xconfig".

Eric

tntcoder · 05-23-2006, 06:21 PM

Thanks for that, right i compiled a new kernel, and added it to lilo, when i boot and select it i get:

VFS: Cannot open root device "802" or unknown-block (8,2)
Please append a correct "root=" boot option
Kernel Panic-not syncing: VFS: unable to mount root fs on unknown block(8,2)

Am i correct in thinking this is a problem with lilo? Im fairly sure its configured correctly here it is:

Code:

# LILO configuration file
boot = /dev/sda
message = /boot/boot_message.txt
prompt
timeout = 1200
# Override dangerous defaults that rewrite the partition table:
change-rules
  reset

vga = normal

default=Linux

other = /dev/sda1
	label="Windows"
  table = /dev/sda
# Windows bootable partition config ends

# Linux bootable partition config begins
image="/dev/sda1"

image="/dev/sda1"
	root="/dev/sda2"

image="/boot/vmlinuz"
	root="/dev/sda2"
	label="Linux"
  read-only

image=/boot/vm-linuz-2.6.16.18
	label=newkernel
	root=/dev/sda2
read-only
# Linux bootable partition config ends

If it helps the lilo gui in kde says its an invalid config

the kernel image file is definatly /boot/vm-linuz-2.6.16.18

EDIT: I did include the correct file systems in the kernel.

Any ideas on what ive done wrong?

prozac · 05-24-2006, 12:39 AM

Quote:

# Linux bootable partition config begins
image="/dev/sda1"

image="/dev/sda1"
root="/dev/sda2"

what are these? i think you should get rid of them
here's a sample lilo.conf file use it as reference:

Quote:

# LILO configuration file
# generated by 'liloconfig'
#
# Start LILO global section
#append="hdd=ide-scsi apm=power-off"
boot = /dev/hda
message = /boot/boot_message.txt
prompt
timeout = 60
# Override dangerous defaults that rewrite the partition table:
change-rules
reset
# Normal VGA console
vga = normal
menu-title = " john.omega.com "
# VESA framebuffer console @ 1024x768x64k
# vga=791
# VESA framebuffer console @ 1024x768x32k
# vga=790
# VESA framebuffer console @ 1024x768x256
# vga=773
# VESA framebuffer console @ 800x600x64k
# vga=788
# VESA framebuffer console @ 800x600x32k
# vga=787
# VESA framebuffer console @ 800x600x256
# vga=771
# VESA framebuffer console @ 640x480x64k
# vga=785
# VESA framebuffer console @ 640x480x32k
# vga=784
# VESA framebuffer console @ 640x480x256
# vga=769
# End LILO global section
password = 7nationarmy
# Linux bootable partition config begins
image = /boot/vmlinuz-ide-2.6.16.5
root = /dev/hda2
label = Linux-2.6.16.5
read-only
# Linux bootable partition config ends
# Linux bootable partition config begins
image = /boot/vmlinuz-ide-2.4.31
root = /dev/hda2
label = Linux
read-only
# Linux bootable partition config ends

note some lines i don't use i have commented out and lilo takes the first image entry as default. here's my Linux-2.6.16.5 is the default.

Alien Bob · 05-24-2006, 05:58 AM

Quote:

Originally Posted by tntcoder

VFS: Cannot open root device "802" or unknown-block (8,2)
Please append a correct "root=" boot option
Kernel Panic-not syncing: VFS: unable to mount root fs on unknown block(8,2)

That would be an indication of the fact that the filesystem drivers for your boot partition are not included in the kernel but built as kernel modules (this is the way the Slackware 2.6 kernel is built nowadays). You will need to build an initrd that includes the drivers for your filesystem (jbd and ext3 if yours is a ext3 filesystem, or reiserfs in case you run reiser as your filesystem).

Boot the computer into an older working kernel, and then build an initrd for the new kernel:

Code:

mkinitrd -c -k 2.6.16.18 -m jbd:ext3

(the example assumes a 2.6.16.18 kernel), and then add a line "initrd = /boot/initrd.gz" to /etc/lilo.conf:

Code:

image=/boot/vm-linuz-2.6.16.18
  label=newkernel
  root=/dev/sda2
  initrd = /boot/initrd.gz
  read-only

and re-run lilo.

Or recompile the kernel and change the drivers jbd, ext3 and reiserfs from modules to built-ins.

Eric

prozac · 05-24-2006, 06:19 AM

it could be very well like Alien-Bob said you should make all your neccessary filesystems modules as built-in and not modules. its pretty much clearly stated in kernel howto if i still remember.

tntcoder · 05-24-2006, 07:00 AM

Thanks for that, i was sure though that i said Y to the ext3 file system rather than M, but i will try this anyway.

Where exactly do i run the initrd command from? It cant seem find the said modules in the kernel build directory.

Also as prozac said i seem to have an irrelevent entry in lilo ive corrected this now.

Alien Bob · 05-24-2006, 07:15 AM

Quote:

Originally Posted by tntcoder

Where exactly do i run the initrd command from? It cant seem find the said modules in the kernel build directory.

You have to run the mkinitrd command from the /boot directory, I forgot to add that. I updated my Wiki page with a paragraph on building an initrd as well: http://alien.slackbook.org/dokuwiki/...kernelbuilding

Eric

tntcoder · 05-24-2006, 07:27 AM

Sorry for being a complete noob here

, but i cant seem to see a new paragraph regarding initrd on your wiki, i have hard refreshed to

, by the way thanks very much for making that tutorial its really good.

I have ran the command from /boot in 2 versions, but i get:

Code:

root@tserver:/boot# mkinitrd -c -k 2.6.16.18 -m jbd:ext3
WARNING:  Could not find module for "jbd"
WARNING:  Could not find module for "ext3"

root@tserver:/boot# mkinitrd -c -k vm-linuz-2.6.16.18 -m jbd:ext3
find: /lib/modules/vm-linuz-2.6.16.18: No such file or directory
WARNING:  Could not find module for "jbd"
find: /lib/modules/vm-linuz-2.6.16.18: No such file or directory
WARNING:  Could not find module for "ext3"

Any ideas what im doing wrong :s

Code:

root@tserver:/boot# ls
README.initrd          config                   map
System.map             config-custom-2.6.16.18  vm-linuz-2.6.16.18
System.map-2.6.16.18   config-ide-2.4.31        vmlinuz
System.map-ide-2.4.31  diag1.img                vmlinuz-ide-2.4.31
boot.0800              initrd-tree
boot_message.txt       initrd.gz

Im not sure what that current initrd.gz is?

Thanks
Jack

prozac · 05-24-2006, 07:56 AM

why don't you compile your kernel again, this time carefully watching what you check-in and what you check-out. saves you lot of trouble.

Alien Bob · 05-24-2006, 07:57 AM

Oops sorry... the modified Wiki page is online now.

Regarding those errors about WARNING: Could not find module for "jbd", it looks like your jbd and ext3 drivers are not available as modules, i.e. you built them into your kernel. If you do have an ext3 filesystem on your root partition and still get kernel panics with this kernel, could it be that you are missing a SCSI or a SATA driver for your disk controller? I noticed you refer to "/dev/sda2" which indicates as much. You might have to create an initrd containing those missing modules, or add the appropriate scsi/sata driver(s) into your kernel.

Eric

masonm · 05-24-2006, 08:03 AM

Quote:

Could not find module for "ext3"

Did you remember to make modules_install when you compiled the kernel?

The lilo.conf you posted is seriously screwed up with entries that make no sense. Follow prozac's example.

For mkinitrd the command is mkinitrd -c -k <your kernel version> -m <your root filesystem type (reiserfs, ext3, etc...>

tntcoder · 05-24-2006, 08:07 AM

Yes i did run the make modules_install, but as i said im pretty sure i said Yes to ext3 in the menu config rather than the module option, so maybe they never got made as modules :s I have fixed lilo now, do i need to start from scratch and build the file system is as modules or is there another way?

prozac · 05-24-2006, 08:13 AM

kernel's are not something you compile and run everyday (unless you are a super geek). so it pays later when you build a kernel that suits your need perfectly instead of having to adjust everytime you reboot. so my suggestion would be to log back in using your old kernel. make a fresh compile giving due consideration to each and every option under make menuconfig and then reach for your lilo.conf for final adjustments. trust you will be a lot happier.