Add reboot-cause information to telemetry

doc/system-telemetry/reboot-cause.md

@@ -11,78 +11,73 @@
 
 ### Enable sonic streaming telemetry agent to send Reboot-cause information
 
-##### Part 1 
-For 1st part, process-reboot-cause copies the previous-reboot-cause.txt 
-to "/host/reboot-cause/previous-reboot-cause/" with adding timestamp 
-at the end of file name after processing the reboot-cause.
+#### Part 1
+During the boot, the process-reboot-cause processes the last reboot-cause based on the hardware reboot-cause
+and the software reboot-cause information and creates previous-reboot-cause.txt with the information.
+To log upto 10 entries of the previous reboot-cause, `process-reboot-cause` will save the previous reboot cause information
+to "/host/reboot-cause/previous-reboot-cause/" with adding timestamp at the end of file name after processing
+the reboot-cause and create a symbolic link.
 Currently previous-reboot-cause.txt is plain text format but this file content will be formatted to be parsed easily.
-Read each reboot-cause information from saved previous-reboot-cause files
-And update reboot-cause information up to 10 entries to state-DB.  
 
 The example shows the previous reboot-cause files stored in /host/reboot-cause/previous-reboot-cause/.
 ```
 $ls /host/reboot-cause/previous-reboot-cause/
 previous-reboot-cause-20200903T232033.txt
 previous-reboot-cause-20200902T101105.txt
 previous-reboot-cause-20200902T015048.txt
+...
 ```
 The following example shows the content of the previous reboot-cause file - previous-reboot-cause-20200903T232033.txt.
 ```
 TIMESTAMP: "20200903T232033"
 CAUSE: "reboot"
 USER: "admin"
 TIME: "Thu 03 Sep 2020 11:15:30 PM UTC"
-COMMENT: "User issued 'reboot' command [User: admin, Time: Thu 03 Sep 2020 11:15:30 PM UTC]" 
+COMMENT: "User issued 'reboot' command [User: admin, Time: Thu 03 Sep 2020 11:15:30 PM UTC]"
 ```
 
-Details of CLI and state-DB given below. 
-Cli command to retrieve the Reboot-cause information
-```
-$ show reboot-cause
-```
-state-DB schema to store the Reboot-cause information
+#### Part 2
+A new service which will retrieve the saved reboot-cause files and read each reboot-cause information from the files
+and update reboot-cause information up to 10 entries to state-DB.
+Verify the information from state-DB data is available via the cli command `show reboot-cause history` which is extended from `show reboot-cause`.
+
+##### Reboot Cause Schema in state-DB
+
+Here is the definition of Reboot-cause schema which will be stored in state-DB.
 ```
 ; Defines information for reboot-cause
-key                     = REBOOT_CAUSE|timestamp         ; last reboot-cause processing time
+key                     = REBOOT_CAUSE|<timestamp>         ; last reboot-cause processing time
 ; field                 = value
 cause                   = STRING                         ; last reboot cause
 time                    = STRING                         ; time when the last reboot was initiated
 user                    = STRING                         ; user who the last reboot initiated
 comment                 = STRING                         ; unstructured json format data
 ```
-Along with data new entry for timestamp will be added up to 10 entries in state_db:  
-
-```
-REBOOT_CAUSE|timestamp
-```
-
-##### Part 2
-Verify that from state-DB data is available via telemetry agent
 
 ##### CLI output  and corresponding structure in state-DB for reboot-cause information
 
 ###### reboot-cause information
 
-Currently `show reboot-cause` displays the last reboot-cause and performing `cat /host/reboot-cause/previous-reboot-cause.txt` to show the reboot-cause. 
-With new design, the reboot-cause will be read from state-DB and displayed with new format.
-`show reboot-cause history` will be added and displays the previous `reboot-cause` up to 10 entries from state-DB.
+Currently `show reboot-cause` displays the last reboot-cause and performing `cat /host/reboot-cause/previous-reboot-cause.txt` to show the reboot-cause.
+This will be same as current design.
+With new design, `show reboot-cause history` will be added to display the previous `reboot-cause` up to 10 entries from state-DB.
 
 The example shows the output of `show reboot-cause` which is same as current output and displays only the last reboot-cause.
 ```
 $ show reboot-cause
 User issued 'reboot' command [User: admin, Time: Thu 03 Sep 2020 11:15:30 PM UTC]
 ```
-Above output will be stored inside state-DB as follows for the reboot-cause information
+Above output will be stored in the previous-reboot-cause.txt file and the reboot-cause information is also stored in state-DB as follows.
 ```
 REBOOT_CAUSE|20200903T112033
-"cause"  
-"reboot"  
-"time"  
-"Thu 03 Sep 2020 11:15:30 PM UTC"  
-"user"  
-"admin"  
-"comment"  
-"User issued 'reboot' command [User: admin, Time: Thu 03 Sep 2020 11:15:30 PM UTC]"  
+"cause"
+"reboot"
+"time"
+"Thu 03 Sep 2020 11:15:30 PM UTC"
+"user"
+"admin"
+"comment"
+"User issued 'reboot' command [User: admin, Time: Thu 03 Sep 2020 11:15:30 PM UTC]"
 ```
 
 The example shows the output of `show reboot-cause history` and the previous reboot cause stored in state-DB in addition to the last reboot-cause.
@@ -96,23 +91,23 @@ TIMESTAMP       REBOOT-CAUSE        Details
 Above output will be stored inside state-DB as follows for the previous reboot-cause in addition to the last reboot-cause
 ```
 REBOOT_CAUSE|20200902T101105
-"cause"  
-"Unknown"  
-"time"  
+"cause"
+"Unknown"
+"time"
 ""
-"user"  
+"user"
 ""
-"comment"  
+"comment"
 "Unknown"
 ```
 ```
 REBOOT_CAUSE|20200902T015048
-"cause"  
-"fast-reboot"  
-"time"  
-"Wed 02 Sep 2020 01:48:33 AM UTC"  
-"user"  
-"admin"  
-"comment"  
-"User issued 'fast-reboot' command [User: admin, Time: Wed 02 Sep 2020 01:48:33 AM UTC]"  
+"cause"
+"fast-reboot"
+"time"
+"Wed 02 Sep 2020 01:48:33 AM UTC"
+"user"
+"admin"
+"comment"
+"User issued 'fast-reboot' command [User: admin, Time: Wed 02 Sep 2020 01:48:33 AM UTC]"
 ```