Why you need backup of your Linux machine? Because you are using Linux so long and had customised according to your needs and you may need to reinstall your Linux in near future. By doing it you can save headaches regarding your customised system and time off-course. This feature is not present in Windows, so if you are new Linux user then you might not know how to backup and restore your customised system. You can backup packages as well as whole system. If you are going to backup whole system then you can restore to your customised system as it is after reinstall. Isn't it great! 

Now, I am taking you to make backup of your Ubuntu machine. You can make your backup on your hard disk as well as on CD/DVD. For making CD/DVD you need to make iso file. Making a backup on a CD/DVD has advantage that you can just format whole of your hard disk and you do not need to bother about partitions where backup of the system is present. There are lot of tools available for this but I am recommending only two tools which I have tried and pretty sure of its easy working-

1)Remastersys

2)Aptoncd

To use them, you need to install first with apt-get. You can find "howto" to install from their respective site. Just add their repository in synaptic and get it downloaded and installed in few minutes. This is not pretty hard.

Now real thing comes. Using Aptoncd you can create backup of all cache packages present in your Linux machine which you have downloaded earlier depending upon your requirements. You can off-course select packages manually for backup. To do this select those packages which you want in backup after whole information about your cache packages is displayed to you. You will also find ISO file created on your hard disk. You can burn this "ISO" file to CD or DVD. So, choose your mode either CD or DVD for burning earlier before creation of "iso" file. If size is larger then 700MB and you have selected CD  mode then you will get mutiple "iso" files to burn over multiple CD's. Aptoncd work's great when you have bootable CD of Ubuntu and you want to add your packages later from backup CD or DVD after fresh install . To do this you just need to restore your packages from "backup CD/DVD" to your synaptic.  Now you will find your backup packages over synaptic and you will install them like normal installation of synaptic.

What about making backup of your whole system ? You can do this using Remastersys. Rather, you will many options under it and I am recommending you Remastersys instead of aptoncd. Why? Because you can backup your customised system with or without user files udner "/home" directory.  If you are happy with terminal then you can use any of commands you need-

sudo remastersys backup

sudo remastersys backup custom.iso

sudo remastersys clean

sudo remastersys dist

sudo remastersys dist cdfs

sudo remastersys dist iso custom.iso

You can also use GUI of remastersys which is really pretty easy to use. By default you will find backup in /home/remastersys folder. When you want to backup your system without user /home files then it is called distribution backup. You can also make distributable iso by selecting cdfs system from options available in GUI window. This will make your Bootable Linux CD/DVD which can be used for reinstallation directly. For any problems just contact their support centre. Thanks and Good luck.