9.Back up your data
No matter where your expertize level is, or the current state of your hardware, nobody is immune to a bad cockpit error, a technical failure, a heavy thunderstorm, a cup of tea/coffee spilt on the keyboard, or the cat messing around with the central unit …
The hard dish drive capacities are increasing every day and we are tempted to store on them more and more data (family pictures, videos, private copies of movies, etc …). The risk of losing a large amount of data also increase at the same time, and that's why we advise you to execute regular backups of your personal data, as well as your passwords and email messages.
This section will endeavor to provide you with simple keys to avoid the lost of your favorite files during a hardware or software failure.
The "cloud" is fashionable these days. Several on-line services are at your disposal to save your data on an external server… 
First of all, you are not immune to a server failure, and secondly, you have no real control on what your data are going to be used for. The "cloud" is actually the computer of someone else, as user Bibi told us recently.
I strongly advise you, in case of doubts (all services are not subsidiaries of the NSA …) to backup your data locally, that is on your own physical medium which you fully control.
9.1.Choosing the medium
Backups used to be made on floppy disks, then on CDs and then on DVDs. Eben if you can still use this kind of support, the technology now gives you access to larger capacities at little cost.
Depending on the amount of the data to backup, you can find external disk from 1GB (USB key type) to 2TB (2000GB), being powered directly over the USB cable, or by an external power supply. The prices range roughly from 5 to 200 US$, depending the capacity.
Of course, if the size of your data is below 700MB, you can use a CD-RW (re-writable CD-Rom) for your backups.
9.2.Graphical mode applications
Debian hosts in its repositories several utilities112 in the "copy and synchronization" section, each of them offers a graphical interface or "client". Here we present one of the simplest backup tool: Déjà-Dup.
Déjà Dup is more than enough to backup your personal data , but if you want to execute a "full system backup " (including your application and the whole installation) you must use more complex software , as described in the Debian documentation 113 .
9.2.1.Backing Up with Déjà-Dup
Déjà-Dup 114 is a "simplified backup tool", which is a graphical interface to the Duplicity software 115 . It allows building secured backup s of your data within a local folder, an external disk, a local network, a remote network or somewhere in the " cloud ".
It also allows the complete encryption and password protection of your backup files.
Déjà-Dup offers a clear interface which does not require any computer knowledge.
Installation
Déjà-Dup can be found in the Debian repositories .To install it using a terminal in administrator mode ( see chap.3.8.3 ):
apt-get update && apt-get install deja-dup
Or using the graphical interface s (chap.8.3), look for "deja-dup".
First launch and configuration
Déjà-Dup will be accessible from the application menu > "Utilities" > " Backup s". During the first launch, the Déjà-Dup settings let you define how to automatically execute the future backup s, where to save, what to save and with which frequency.
Déjà-Dup: selection of the folders to save
Déjà-Dup:selection of the folder to ignore
Déjà-Dup: selection of the storage location
Déjà-Dup: scheduling the
backup
s
Saving your data
Once the settings are done, launch the first backup by clicking on the " Back Up Now" button residing under the "Overview" tab.
The very first backup execution will take some time, depending on the size of the data to be saved, but the following runs should be a lot faster since they will save only the modified files: this is the incremental backup.
An additional feature is the optional password setting during the configuration, which allows the encryption of the full set of backups:
Déjà-Dup: protecting your
backup
Déjà-Dup: launching the
backup
Restoring your data
To restore a backup on a newly installed system, for example, simply install Déjà-Dup on it, launch it and select "Restore" in the main window.
A series of simple windows will help you to find and restore your data:
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Define the restore from which location:
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Define the restore destination:
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confirm the restore parameters:
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If the backup has been encrypted, the password will be required, then the restore process will begin. An information window is displayed at the end of the process.
Déjà-Dup: restoring data
Déjà-Dup: restore process completed
9.3.Manual method
If you want to save just one folder or few of them, you can simply use the file system manager, or your archive manager (to reduce the storage space through compression).
The latter produces "real" archives: for subsequent consultation of these data, you need to uncompress the archive.
From the file manager, select the folders to be saved, then right-click and take the "Compress…" (or "Archive") action.
Then you just have to move the archive on an external medium.
9.4.Cloning the system
This is the complete solution ensuring a total safety for your data: cloning the entire hard disk.
Clonezilla Live 116 is a Live CD based on the Debian GNU/Linux distribution, which includes the Clonezilla2 software . It allows the user to directly execute from its machine:
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A Backup : copy the entire disk copy , or one or several partition s, under the form of an image and save it on any kind of storage.
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A Restore : restore an image from its storage location (to the same disk, another disk, another machine, a USB key, a network, etc.).
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A Copy : direct copy from an original disk to another destination disk.
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This Clonezilla version is able to connect to different servers: SSH server, Samba server, NFS server …
As its name suggests it, it works like a Live CD (CD-ROM, DVD-ROM) but can also be executed from a USB key, an external disk, etc. (source Wikipédia117 )
You can find an English tutorial on this page118.
112 https://www.debian.org/doc/manuals/debian-reference/ch10.html#_copy_and_synchronization_tools
113 https://wiki.debian.org/BackupAndRecovery
114 https://wiki.gnome.org/Apps/DejaDup
115 http://duplicity.nongnu.org/
117 https://en.wikipedia.org/wiki/Clonezilla
118 https://www.howtoforge.com/back-up-restore-hard-drives-and-partitions-with-clonezilla-live