Kdump now works on live images with some manual configurations. Here is the step
by step guide.

1. Enable crashkernel reservation

Since there isn't any config file that can be used to configure kernel
parameters for live images before booting them, we have to append 'crashkernel'
argument in boot menu every time we boot a live image.

2. Change dump target in /etc/kdump.conf

When kdump kernel boots in a live environment, the default target /var/crash is
in RAM so you need to change the dump target to an external disk or a network
dump target.

Besides, make sure that "default dump_to_rootfs" is not specified.

3. Start kdump service

    $ kdumpctl start

4. Trigger a kdump test

    $ echo 1 > /proc/sys/kernel/sysrq
    $ echo c > /proc/sysrq-trigger