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Joined: 15 Dec 2017
Posts: 16

PostPosted: Wed Jan 16, 2019 10:57 am    Post subject: Order of kernel rebuild steps Reply with quote

I have a script to rebuild the kernel after updating or config changes.
It includes: kernel building, modules building, installing initramfs with lvm and luks, rebuilding external modules (e.g. nvidia drivers) and updating grub config.

Here is the script:


set -x
set -e

cd linux

# mount boot if not mounded
mount | grep "/boot type vfat" > /dev/null || mount /boot

# build the kernel
make -j16

# install modules
make modules_install

# prepare modules (for @module-rebuild)
make modules_prepare

# rebuild external modules (nvidia, etc)
emerge --ask=n @module-rebuild

# install kernel
make install

# build initramfs
genkernel --lvm --luks --install initramfs

# make grub config
grub-mkconfig > /boot/grub/grub.cfg

# umount boot
umount /boot

this script is working fine, but with one exception: I always need to call it twice, if I don't I'll get error on boot (failed to load initramfs), I think that some steps in script has wrong order, but I can't figure out what steps exactly. Oficial docs doesn't cover rebuilding with initramfs:

What's wrong with my script? How to update it to fix?

Also asked same question here:
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Joined: 22 Sep 2004
Posts: 173

PostPosted: Wed Jan 16, 2019 4:44 pm    Post subject: Reply with quote

Isn't genkernel supposed to build the kernel anyway? Maybe genkernel has some issues with generating just the initramfs for a kernel that has already been built and installed...

My routine is
genkernel --no-splash all && emerge @module-rebuild && grub-mkconfig -o /boot/grub/grub.cfg && umount /boot

I don't mount /boot because I have it set in /etc/genkernel.conf:
# Configuration file for genkernel

All I have to do is copy the .config from the previous kernel, run "make listnewconfig" to get an overview, then "make oldconfig" to set the new options, and go with my genkernel command routine I wrote above.

I have no problems so far. I'm sorry I cannot be of more help, but my guess is really that genkernel doesn't correctly build the initramfs for you...
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Joined: 25 Jul 2006
Posts: 3548
Location: Illinois, USA

PostPosted: Wed Jan 16, 2019 5:26 pm    Post subject: Reply with quote

My build script, modify as required:

#test if running on a bare VT
if [ "$TERM" = linux ]; then
    TERM=xterm     #so make munuconfig will display correctly

cd /usr/src/linux
zcat /proc/config.gz >.config
#cp /boot/config-4.17.19-gentoo .config
#test for backporting nct6775.c
LONGVER=$(uname -r)
SHORTVER=$(echo -n $LONGVER | cut -f1,2 -d'.')
if [ $SHORTVER = 4.4 ] || [ $SHORTVER = 4.9 ]; then
 cp /usr/src/new_nct6775.c drivers/hwmon/nct6775.c

# At this point we should compare kernel versions and make oldconfig if the base version has updated
make oldconfig
make menuconfig
make -j5 || {  echo "make -j5 failed"; exit 1; }
make -j5 modules_install || { echo "make modules_install failed";  exit 2; }
make -j5 install && echo "Don't forget to update boot loader menu"

# kver="$(eselect kernel list | awk '{gsub("linux-","") ; if ($3 ~ "*") print $2}')"
# i.e. kver contains 4.9.9-gentoo

#virtualbox modules
echo "Building Virtualbox modules"
emerge @module-rebuild
echo "Done"

This depends on having the kernel config built into the kernel which is a good idea anyway.
The nct6775.c stuff is because I have a newer motherboard that wasn't supported by the old nct6775.c but was in newer kernels. That may have been backported now. If you don't have an MSI Tomahawk B350, just erase it.
The commented out second line is for use in the case when the config is not in the kernel. Modify it as appropriate and then select "config in kernel" in make menuconfig.
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