Implement some best practice and mysql example

scripts/backup

@@ -1,4 +1,8 @@
 #!/bin/bash
+
+# causes the shell to exit if any subcommand or pipeline returns a non-zero status
+set -e
+
 app=ynhexample
 
 # The parameter $1 is the backup directory location
@@ -9,6 +13,10 @@ sudo mkdir -p $backup_dir
 # Backup sources & data
 sudo cp -a /var/www/$app/. $backup_dir/sources
 
+# Backup mysql database if needed
+# db_pwd=$(sudo yunohost app setting $app mysqlpwd)
+# sudo mysqldump -u $app -p$db_pwd $app > $backup_dir/$app.dmp
+
 # Copy Nginx and YunoHost parameters to make the script "standalone"
 sudo cp -a /etc/yunohost/apps/$app/. $backup_dir/yunohost
 domain=$(sudo yunohost app setting $app domain)