BTW
The problem has been solved in AskUbuntu S&E and it introduces grub2-probe because grub.cfg after kernel updating scripts being broken.
Review your grub.cfg for lost indent and repeat grub2-mkconfig.
Detailed description about updating kernel via yum:
CentOS distributes kernel via RPM packages and stores it in own repository.
When you work with repository you install/remove/reinstall ... RPM packages.
RPM packages that stores kernel has postinst and posttrans sections that do all necessary steps to adopt new kernel in CentOS. This steps include several important things like initramfs generation, set new entries in bootloader ...
Lets see in 3.10.0-957.el7.x86_64.rpm postinstall sections:
postinst:
/usr/sbin/new-kernel-pkg --package kernel --install 3.10.0-957.el7.x86_64 || exit $?
posttrans:
if [ -x /usr/sbin/weak-modules ]
then
/usr/sbin/weak-modules --add-kernel 3.10.0-957.el7.x86_64 || exit $?
fi
/usr/sbin/new-kernel-pkg --package kernel --mkinitrd --dracut --depmod --update 3.10.0-957.el7.x86_64
rc=$?
if [ $rc != 0 ]; then
/usr/sbin/new-kernel-pkg --remove 3.10.0-957.el7.x86_64
ERROR_MSG="ERROR: installing kernel-3.10.0-957.el7.x86_64: no space left for creating initramfs. Clean up /boot partition and re-run '/usr/sbin/new-kernel-pkg --package kernel --mkinitrd --dracut --depmod --install 3.10.0-957.el7.x86_64'"
if [ -e /usr/bin/logger ]; then
/usr/bin/logger -p syslog.warn "$ERROR_MSG"
elif [ -e /usr/bin/cat ]; then
/usr/bin/cat "$ERROR_MSG" > /dev/kmsg
fi
echo "$ERROR_MSG"
exit $rc
fi
/usr/sbin/new-kernel-pkg --package kernel --rpmposttrans 3.10.0-957.el7.x86_64 || exit $?
These postinstall scripts using new-kernel-pkg script which is the part of grubby project. man 8 new-kernel-prkg writes:
Description
new-kernel-pkg is a tool used in packaging to automate the
installation of a new kernel, including the creation of an initial ram
filesystem image, updating of bootloader configuration, and other
associated tasks
new-kernel-pkg script calls grubby (it's program inside grubby project) to update bootloader configuration. From man 8 grubby:
Description
grubby is a command line tool for updating and displaying information
about the configuration files for the grub, lilo, elilo (ia64), yaboot
(powerpc) and zipl (s390) boot loaders. It is primarily designed to be
used from scripts which install new kernels and need to find
information about the current boot environment.
Fragment of calling grubby from new-kernel-pkg script:
ARGS="--grub2 -c $grub2Config --add-kernel=$kernelImage $INITRD \
--copy-default --title \"$title\$debugtitle\" \
${mbkernel:+--add-multiboot=\"$mbkernel\"} \
${mbargs:+--mbargs=\"$mbargs\"} \
--args=\"root=$rootdevice $kernargs \$debugargs\" \
--remove-kernel=\"TITLE=$title\$debugtitle\""
rungrubby ${ARGS} $makedefault
If you need to know more specific info about how bootloader configuration are being builded you can run new-kernel-pkg (involving neccessary kernel version and parameters) with verbose mode (-v option).
So, there is no necessary to call grub2-mkconfig manually after kernel updating.
