Documentation: step by step guide on confiuring kdump in live images

This is a short document about how to setup kdump on live images. All
steps were tested on Fedora 25 Alpha LiveCD and saved vmcore captured
by kdump to a USB stick successfully.

Signed-off-by: Tong Li <tonli@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>

kexec-tools.spec

@@ -29,6 +29,7 @@ Source23: kdump-anaconda-addon-005-19-g6577df4.tar.gz
 Source24: kdump-lib-initramfs.sh
 Source25: kdump.sysconfig.ppc64le
 Source26: kdumpctl.8
+Source27: live-image-kdump-howto.txt
 
 #######################################
 # These are sources for mkdumpramfs
@@ -154,6 +155,7 @@ rm -f kexec-tools.spec.in
 # setup the docs
 cp %{SOURCE10} .
 cp %{SOURCE21} .
+cp %{SOURCE27} .
 
 make
 %ifarch %{ix86} x86_64 ppc64 s390x ppc64le
@@ -326,6 +328,7 @@ done
 %doc TODO
 %doc kexec-kdump-howto.txt
 %doc kdump-in-cluster-environment.txt
+%doc live-image-kdump-howto.txt
 %ifarch %{ix86} x86_64 ppc64 s390x ppc64le
 %{_libdir}/eppic_makedumpfile.so
 /usr/share/makedumpfile/eppic_scripts/

live-image-kdump-howto.txt

@@ -0,0 +1,23 @@
+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.
+
+3. Start kdump service
+
+    $ kdumpctl start
+
+4. Trigger a kdump test
+
+    $ echo 1 > /proc/sys/kernel/sysrq
+    $ echo c > /proc/sysrq-trigger