Reinforce configuration

So it breaks early if something is wrong, allows more flexibility with
the bwlimit setting, and adds default values so you don't have to have
everything in the configuration file.

Signed-off-by: Robert Spencer <rspencer@lbsd.net>

scripts/backstep-traceback-auto

@@ -56,24 +56,47 @@ if not os.path.exists(CONFIG_FILE):
     print("error: backup is not configured.")
     sys.exit(2)
 
-config = configparser.ConfigParser()
+config_default_dict = {
+    "debug_max_load": "20",
+    "max_load": "8",
+    "report_email": "hostmaster@iitsp.net",
+    "zabbix_config": "/etc/zabbix/zabbix_agentd.conf.d/allworldit.conf",
+    "server_path": "backup",
+    "server_key": "/root/.ssh/backupserver_id_rsa",
+}
+config = configparser.ConfigParser(defaults=config_default_dict)
 config.read(CONFIG_FILE)
 
-bwlimit = config.get(PERIOD, "bwlimit")
-debug_max_load = config.get(PERIOD, "debug_max_load")
-max_load = config.get(PERIOD, "max_load")
+bwlimit = config.getint(PERIOD, "bwlimit", fallback=None)
+debug_max_load = config.getint(PERIOD, "debug_max_load")
+max_load = config.getint(PERIOD, "max_load")
 report_email = config.get(PERIOD, "report_email")
 server_host = config.get(PERIOD, "server_host")
 server_key = config.get(PERIOD, "server_key")
+
+if not os.path.exists(server_key):
+    print("error: " + server_key + " does not exist.")
+    sys.exit(2)
+
 server_path = config.get(PERIOD, "server_path")
-server_port = config.get(PERIOD, "server_port")
+server_port = config.getint(PERIOD, "server_port")
 server_user = config.get(PERIOD, "server_user")
 zabbix_config = config.get(PERIOD, "zabbix_config")
 
+if not os.path.exists(zabbix_config):
+    print("error: " + zabbix_config + " does not exist.")
+    sys.exit(2)
+
 if args.verbose:
-    syncopts = ["--debug", "--max-load=" + debug_max_load]
+    syncopts = ["--debug"]
+    syncopts.append("--max-load=" + str(debug_max_load))
 else:
-    syncopts = ["--max-load=" + max_load, "--quiet", "--bwlimit=" + bwlimit]
+    syncopts = ["--quiet"]
+    syncopts.append("--max-load=" + str(max_load))
+
+    if bwlimit:
+        if bwlimit > 0:
+            syncopts.append("--bwlimit=" + str(bwlimit))
 
 for lv in ast.literal_eval(config.get(PERIOD, "backup_lvs")):
     if args.only and args.only != lv:
@@ -110,21 +133,15 @@ for lv in ast.literal_eval(config.get(PERIOD, "backup_lvs")):
     command_line.extend(bind_mount_args)
     command_line.append('--email-subject="' + PERIOD.upper() + " " + lv + '"')
     command_line.append("--email=" + report_email)
-    command_line.extend(["--port=" + server_port, "--pubkey=" + server_key])
+    command_line.append("--port=" + str(server_port))
+    command_line.append("--pubkey=" + server_key)
     command_line.extend(syncopts)
-    command_line.extend(["--zabbix=" + ZABBIX_ITEM, "--zabbix-config=" + zabbix_config])
+    command_line.append("--zabbix=" + ZABBIX_ITEM)
+    command_line.append("--zabbix-config=" + zabbix_config)
     command_line.append(
-        server_user
-        + "@"
-        + server_host
-        + "::"
-        + server_path
-        + "/"
-        + PERIOD
-        + "-"
-        + VG
-        + "-"
-        + lv
+        "{}@{}::{}/{}-{}-{}".format(
+            server_user, server_host, server_path, PERIOD, VG, lv
+        )
     )
 
     EXIT_CODE = subprocess.call(command_line)