Update install.md

doc/install.md

@@ -73,9 +73,11 @@ Stop SOCTools without destroying containers:
 Restart SOCTools after it has been stopped with `stop-docker-containers` tag:
 * `ansible-playbook -i inventories soctools.yml -t start-docker-containers`
 
-Delete SOCTools containers:
+Destroy SOCTools containers:
 * `ansible-playbook -i inventories soctools.yml -t destroy-docker-containers`
 
+Deletion of the SOCTools containers will not delete the data in the volumes, and if the deletion of all data is also required, you should also execute the following command:
+* `docker system prune -a`
 
 
 ## Errors building SOCTools