Comment # 2 on bug 1171180 from Andreas Schwab

# get_kernel_version /boot/zImage-5.6.8-1-default ; echo $?
1
panda:~/:[0]# get_kernel_version /boot/vmlinux-5.6.8-1-default.xz ; echo $?
5.6.8-1-default
0
panda:~/:[0]# mkinitrd
No kernel found in /boot or bad modules dir in /lib/modules