website: Update example command-lines in building_arm_kernel

* Deprecate fs.py from the example command-lines in favour of
starter_fs.py

* Point to a more up to date disk image

Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Change-Id: Id4897466c8d023136c35bc5596a2b6f33acbc0d7
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/43183
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
diff --git a/_pages/documentation/general_docs/fullsystem/building_arm_kernel.md b/_pages/documentation/general_docs/fullsystem/building_arm_kernel.md
index 72a1c96..5e22321 100644
--- a/_pages/documentation/general_docs/fullsystem/building_arm_kernel.md
+++ b/_pages/documentation/general_docs/fullsystem/building_arm_kernel.md
@@ -10,7 +10,7 @@
 
 This page contains instructions for building up-to-date kernels for gem5 running on ARM. 
 
-If you don't want to build the Kernel on your own you could still [download a
+If you don't want to build the Kernel (or a disk image) on your own you could still [download a
 prebuilt version](./guest_binaries).
 
 ## Prerequisites
@@ -78,8 +78,8 @@
 Testing the just built kernel:
 
 ```
-./build/ARM/gem5.opt configs/example/fs.py --kernel=/tmp/linux-arm-gem5/vmlinux --machine-type=VExpress_GEM5_V1 \
-    --dtb-file=$PWD/system/arm/dt/armv8_gem5_v1_1cpu.dtb --disk-image=linaro-minimal-aarch64.img
+./build/ARM/gem5.opt configs/example/arm/starter_fs.py --kernel=/tmp/linux-arm-gem5/vmlinux \
+    --disk-image=ubuntu-18.04-arm64-docker.img
 ```
 
 # Legacy kernels (pre v4.x)