GRUB and generic kernel

3rensho · 10-14-2019, 04:18 AM

I am switching over to the generic kernel (4.19.79 at present). Read the README.initrd but it only covers configuring LILO and I use GRUB2. I've built the kernel, modules, firmware, headers and have run the mkinitrd command to create the initrd-tree and initrd.gz in /boot. Ran grub-mkconfig -o /boot/grub/grub.cfg. Is there any other config that I need so that when I reboot the initrd can be found and booting will happen without a problem ??? Thanks in advance.

hazel · 10-14-2019, 05:37 AM

It looks to me as if you have done everything necessary. If you're not sure, you can look at the grub.cfg file and check that the new Slackware stanza contains everything it should and that you still have the old one as a fallback.

colorpurple21859 · 10-14-2019, 05:38 AM

If the default entry isn't the one you want to boot, edit /etc/default/grub and rerun grub-mkconfig, so the the entry you want to use will boot by default.
Another way, which is what I do is create a /etc/grub.d/05_custom with the following entries similar to these, edit the ? to match your system, will put the said entries first in your grub menu.

Code:

menuentry 'Slackware-generic'{
        load_video
        insmod gzio
        insmod part_gpt
        insmod ext2
        set root='hd0,gpt?'
       	echo    'Loading Slackware-generic ...'
        linux   /boot/vmlinuz-generic root=/dev/sda? ro
        initrd /boot/initrd.gz
}

menuentry 'Slackware-huge'{
        load_video
        insmod gzio
        insmod part_gpt
        insmod ext2
        set root='hd0,gpt?'
        echo    'Loading Slackware-Huge...'
        linux   /boot/vmlinuz-huge root=/dev/sda7 ro
        
}

run grub-mkconfig, unless something goes wrong shouldn't have to run grub-mkconfig after a kernel upgrade.

3rensho · 10-14-2019, 05:51 AM

Tried booting. It found initrd

Loading kernel modules from initrd image

insmod loaded jbd2.ko, mbcache.ko, ext4.ko

then coughed blood with

Mount can't find /mnt in /mnt/fstab

Will boot Knoppix and have a look at your suggestion colorpurple

System is Raid 1 with ext4 fs usually mounted on /dev/md126

Didier Spaier · 10-14-2019, 06:13 AM

Don't forget to run:

Code:

grub-install <drive>

where <drive> is the drive's name like /dev/sda for instance.

3rensho · 10-14-2019, 06:37 AM

The system has had grub installed from the get go. The only thing I have changed is moving from the huge kernel to the generic version. After building the kernel and associated bits like modules, firmware and headers I had run mkinitrd and then grub-mkconfig. Why the need to reinstall grub?

hazel · 10-14-2019, 07:17 AM

/mnt/fstab looks weird. I've never seen that before; it should be /etc/fstab. The only thing I can think of is that grub has been given the wrong root partition. Again check your grub.cfg.

3rensho · 10-14-2019, 08:41 AM

I agree Hazel. For now I am building the huge kernel again so I will have a running machine. I'll do further searching as time permits. Thanks to all so far.

hazel · 10-14-2019, 10:06 AM

Why didn't you keep the old kernel as a fallback until you knew the new kernel could boot? It would have saved you a lot of aggro.

Richard Cranium · 10-14-2019, 10:30 AM

https://github.com/Richard-Cranium/SlackwareGrub2 might help.

It assumes that you name your initrd to match the kernel version, i.e. initrd-4.19.79.gz for the 4.19.79 kernel. I use it myself, for what that's worth.

3rensho · 10-14-2019, 12:43 PM

Thanks Richard for that. Will have a look see. Too right Hazel.

Didier Spaier · 10-14-2019, 02:05 PM

The default util/grub.d/10-linux.in in the source archive includes this code snippet:

Code:

  initrd_real=
  for i in "initrd.img-${version}" "initrd-${version}.img" "initrd-${version}.gz" \
       "initrd-${version}" "initramfs-${version}.img" \
       "initrd.img-${alt_version}" "initrd-${alt_version}.img" \
       "initrd-${alt_version}" "initramfs-${alt_version}.img" \
       "initramfs-genkernel-${version}" \
       "initramfs-genkernel-${alt_version}" \
       "initramfs-genkernel-${GENKERNEL_ARCH}-${version}" \
       "initramfs-genkernel-${GENKERNEL_ARCH}-${alt_version}"; do
    if test -e "${dirname}/${i}" ; then
      initrd_real="${i}"
      break
    fi
  done

But in Slackware the initrd is usually just named initrd.gz so inird_real is not set and the line initrd= not fed by grub-mkconfig.

This patch solves that when building grub:

Code:

diff -Naur grub-2.00.orig/util/grub.d/10_linux.in grub-2.00/util/grub.d/10_linux.in
--- grub-2.00.orig/util/grub.d/10_linux.in    2012-04-18 23:24:38.000000000 +0200
+++ grub-2.00/util/grub.d/10_linux.in    2012-06-30 07:53:03.765625589 +0200
@@ -198,7 +198,8 @@
        "initramfs-genkernel-${version}" \
        "initramfs-genkernel-${alt_version}" \
        "initramfs-genkernel-${GENKERNEL_ARCH}-${version}" \
-       "initramfs-genkernel-${GENKERNEL_ARCH}-${alt_version}"; do
+       "initramfs-genkernel-${GENKERNEL_ARCH}-${alt_version}" \
+       "initrd.gz"; do
     if test -e "${dirname}/${i}" ; then
       initrd="$i"
       break

Alternatively, you can patch directly /etc/grub.d/10_linux to avoid rebuilding grub just for that.

Nille_kungen · 10-17-2019, 04:34 AM

The only thing that should differ going from huge to generic kernel is initrd.
If you have problems creating an initrd then /usr/share/mkinitrd/mkinitrd_command_generator.sh might help (it can also be run interactive -i).
You don't need to patch anything /boot/initrd.gz should work by default.

3rensho · 10-17-2019, 04:52 AM

No, I had no problems creating the initrd. It was found at boot and loaded several modules (see above). It was only after that booting gave up apparently looking for an fstab in /mnt/fstab which obviously doesn't exist. I'll get back to trying the generic kernel again in a few days when I have some time.

Firerat · 10-17-2019, 07:03 AM

for kernels and grub I use

( I have added echo so these scripts will only show what is to be done )

Code:

#!/bin/bash

Kernel=(/boot/vmlinuz*-*-*)

for version in ${Kernel[@]}
do
   [[ -e /boot/initrd-${version##*-}.gz ]] || \
   echo mkinitrd \
    -c \
    -k ${version##*-} \
    -f ext4 \
    -r /dev/vg_slackware/lv_root \
    -m usb-storage:ehci-hcd:ehci-pci:uhci-hcd:jbd2:mbcache:crc32c-intel:ext4 \
    -L -l uk -u \
    -o /boot/initrd-${version##*-}.gz
done
echo grub-mkconfig -o /boot/grub/grub.cfg

obviously you will need to adapt it for your setup
The important part is -o /boot.... , this will generate an initrd for each kernel version you have, grub-mkconfig will then happily generate a grub.cfg using the correct initrd for each kernel.

to get multiple kernels. you need to blacklist, and install manually
you can grab the latest kernel packages with this script ( after updating pkg lists )

Code:

#!/bin/bash

mirror="$(grep -m1 -v ^# /etc/slackpkg/mirrors)"
while read pkg
do
  for ext in .txt .txz.asc .txz
  do
    [[ -e ./${pkg#./}${ext} ]]  && continue
    GetList+=(${pkg#./}${ext})
    [[ ${ext} != \.txz ]]          && continue
    Install+=(${pkg##*/})
  done 
done < <(awk '/kernel-[gmh][eo]/{print $7"/"$6}' /var/lib/slackpkg/pkglist)

echo wget -c ${GetList[@]/#/ ${mirror}}

you then install manually, e.g.

Code:

installpkg kernel*79*txz

( or finish my script and use the Install array

)