pkg/kmsg: add simple test case

Signed-off-by: David Scott <dave.scott@docker.com>

test/cases/040_packages/031_kmsg/check.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+for i in $(seq 1 20); do
+	# Look for a common kernel log message
+	if grep "SCSI subsystem initialized" /var/log/kmsg.out 2>/dev/null; then
+		printf "kmsg test suite PASSED\n" > /dev/console
+		/sbin/poweroff -f
+	fi
+	sleep 1
+done
+
+printf "kmsg test suite FAILED\n" > /dev/console
+echo "contents of /var/log/kmsg.out:" > /dev/console
+cat /var/log/kmsg.out > /dev/console
+/sbin/poweroff -f

test/cases/040_packages/031_kmsg/test.sh

@@ -0,0 +1,24 @@
+#!/bin/sh
+# SUMMARY: Check that the kmsg package works
+# LABELS:
+# REPEAT:
+
+set -e
+
+# Source libraries. Uncomment if needed/defined
+#. "${RT_LIB}"
+. "${RT_PROJECT_ROOT}/_lib/lib.sh"
+NAME=kmsg
+
+clean_up() {
+	rm -rf ${NAME}-*
+}
+trap clean_up EXIT
+
+# Test code goes here
+linuxkit build -disable-content-trust -format kernel+initrd -name "${NAME}" test.yml
+RESULT="$(linuxkit run ${NAME})"
+echo "${RESULT}"
+echo "${RESULT}" | grep -q "suite PASSED"
+
+exit 0

test/cases/040_packages/031_kmsg/test.yml

@@ -0,0 +1,32 @@
+kernel:
+  image: linuxkit/kernel:4.14.53
+  cmdline: "console=ttyS0 console=ttyAMA0"
+init:
+  - linuxkit/init:6cc1442112980c889230b6449df09d5b48de6854
+  - linuxkit/runc:v0.4
+  - linuxkit/containerd:f2bc1bda1ab18146967fa1a149800aaf14bee81b
+  - linuxkit/ca-certificates:v0.4
+  - linuxkit/memlogd:883f0d46e7d3ae2d787e8acb496da115a4707cbc
+services:
+  - name: kmsg
+    image: linuxkit/kmsg:3dfa0d5b4027ecc16089f27fbcffa15d6aa5438e
+  - name: write-and-rotate-logs
+    image: linuxkit/logwrite:7859c102a963828fd9c5aa3837db9600483220c7
+  - name: check-the-logs
+    image: alpine:3.8
+    binds:
+      - /check.sh:/check.sh
+      - /dev/console:/dev/console
+      - /var/log:/var/log
+    command: ["sh", "./check.sh"]
+    pid: host
+    capabilities:
+      - CAP_SYS_BOOT
+files:
+  - path: check.sh
+    source: ./check.sh
+trust:
+  org:
+    - linuxkit
+  image:
+    - alpine:3.8