[reboot cause] Move reboot-cause files to /host directory so they per…

…sist across SONiC upgrades (sonic-net#446)

scripts/fast-reboot

@@ -2,7 +2,7 @@
 
 REBOOT_USER=$(logname)
 REBOOT_TIME=$(date)
-REBOOT_CAUSE_FILE="/var/cache/sonic/reboot-cause.txt"
+REBOOT_CAUSE_FILE="/host/reboot-cause/reboot-cause.txt"
 WARM_DIR=/host/warmboot
 REDIS_FILE=dump.rdb
 REBOOT_SCRIPT_NAME=$(basename $0)

scripts/reboot

@@ -6,7 +6,7 @@ PLATFORM=$(sonic-cfggen -H -v DEVICE_METADATA.localhost.platform)
 ASIC_TYPE=$(sonic-cfggen -y /etc/sonic/sonic_version.yml -v asic_type)
 DEVPATH="/usr/share/sonic/device"
 PLAT_REBOOT="platform_reboot"
-REBOOT_CAUSE_FILE="/var/cache/sonic/reboot-cause.txt"
+REBOOT_CAUSE_FILE="/host/reboot-cause/reboot-cause.txt"
 
 function stop_sonic_services()
 {

show/main.py

@@ -1658,7 +1658,7 @@ def mmu():
 @cli.command('reboot-cause')
 def reboot_cause():
     """Show cause of most recent reboot"""
-    PREVIOUS_REBOOT_CAUSE_FILE = "/var/cache/sonic/previous-reboot-cause.txt"
+    PREVIOUS_REBOOT_CAUSE_FILE = "/host/reboot-cause/previous-reboot-cause.txt"
 
     # At boot time, PREVIOUS_REBOOT_CAUSE_FILE is generated based on
     # the contents of the 'reboot cause' file as it was left when the device