diff --git a/modoboa_installer/database.py b/modoboa_installer/database.py
index 0f8c304..1276a12 100644
--- a/modoboa_installer/database.py
+++ b/modoboa_installer/database.py
@@ -61,6 +61,7 @@ class PostgreSQL(Database):
         if dbname and dbuser:
             self._setup_pgpass(dbname, dbuser, dbpassword)
             cmd += " -h {} -d {} -U {} -w".format(self.dbhost, dbname, dbuser)
+        query = query.replace("'", "'\"'\"'")
         cmd = "{} -c '{}' ".format(cmd, query)
         utils.exec_cmd(cmd, sudo_user=self.dbuser)
 
@@ -146,7 +147,8 @@ class MySQL(Database):
         cmd = "mysql -h {} -u {} -p{}".format(self.dbhost, dbuser, dbpassword)
         if dbname:
             cmd += " -D {}".format(dbname)
-        utils.exec_cmd(cmd + """ -e "{}" """.format(query))
+        query = query.replace("'", "'\"'\"'")
+        utils.exec_cmd(cmd + """ -e '{}' """.format(query))
 
     def create_user(self, name, password):
         """Create a user."""
diff --git a/modoboa_installer/scripts/__init__.py b/modoboa_installer/scripts/__init__.py
index cfc287a..c90c436 100644
--- a/modoboa_installer/scripts/__init__.py
+++ b/modoboa_installer/scripts/__init__.py
@@ -18,4 +18,9 @@ def install(appname, config):
     except ImportError:
         print("Unknown application {}".format(appname))
         sys.exit(1)
-    getattr(script, appname.capitalize())(config).run()
+    try:
+        getattr(script, appname.capitalize())(config).run()
+    except utils.FatalError as inst:
+        utils.printcolor(utils.RED, "Failure")
+        print(inst)
+        sys.exit(1)
diff --git a/modoboa_installer/scripts/modoboa.py b/modoboa_installer/scripts/modoboa.py
index a9b5dd9..536e0b7 100644
--- a/modoboa_installer/scripts/modoboa.py
+++ b/modoboa_installer/scripts/modoboa.py
@@ -109,10 +109,12 @@ class Modoboa(base.Installer):
                     self.config.get("amavis", "dbname")
                 )
             ]
-        utils.exec_cmd(
+        code, output = utils.exec_cmd(
             "bash -c '{} modoboa-admin.py deploy instance {}'".format(
                 prefix, " ".join(args)),
             sudo_user=self.user, cwd=self.home_dir)
+        if code:
+            raise utils.FatalError(output)
 
     def get_packages(self):
         """Include extra packages if needed."""
@@ -167,7 +169,7 @@ class Modoboa(base.Installer):
                 settings["modoboa_stats"]["logfile"] = path
         settings = json.dumps(settings)
         query = (
-            "UPDATE core_localconfig SET _parameters='\"'\"'{}'\"'\"'"
+            "UPDATE core_localconfig SET _parameters='{}'"
             .format(settings)
         )
         self.backend._exec_query(