How to permanently remove files in Ubuntu/linux and make them unrecoverable by NickMcDTV
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Tag Archives: USB flash drive
How to shred (permanently delete) files from your Hard Disks on Ubuntu Linux
In our last post we examined the possibility to recover deleted data from USB keys and disks. Today we want to focus your attention on the proper way to destroy sensitive data from your disks.
On Ubuntu you have the possibility to move any file to the Trash but, as we demonstrate in our last post, anyone has the possibility to recover them using a simple, basic GUI, program called PhotoRec.
If you want to be reasonably sure that none will be able to recover a file you decided to permanently delete you have to use the Shred command. Shred is native in Ubuntu Kernel and literally delete your files overwriting them repeatedly with arbitrary data. After you delete a file with Shred you can be sufficiently sure that recovering procedures will not succeed.
As usual we must warn you that technology is rapidly evolving and what could be considered sure today, tomorrow will be out of date! So, if you think you need to preserve your privacy in the best way, don’t forget to change the hard disks regularly and mechanically destroy your old ones. Sincerely we hope our readers haven’t this kind of need.
To start using Shred on Ubuntu you have to open a Terminal and type:
sudo shred –help
In this way you will visualize the grammar and all the possible options offered by this program.
The correct grammar to use Shred is:
shred [OPTIONS] FILE
or, if you want to shred a entire partition:
shred [OPTIONS] /dev/[HDA9]
The possible options are:
-f, –force change permissions to allow writing if necessary
-n, –iterations=N overwrite N times instead of the default (3)
–random-source=FILE get random bytes from FILE
-s, –size=N shred this many bytes (suffixes like K, M, G accepted)
-u, –remove truncate and remove file after overwriting
-v, –verbose show progress
-x, –exact do not round file sizes up to the next full block;
this is the default for non-regular files
-z, –zero add a final overwrite with zeros to hide shredding
–help display this help and exit
–version output version information and exit
In our experience, to operate in the fastest way, we decided to add Shred on the Nautilus Menu and have the command ready with a simple right click on the mouse.
For this reason you have to open a Terminal and type:
sudo apt-get install nautilus-actions
Then you launch the program following this path: System->Preference->Nautilus Actions Configuration.
Last, you have to configure Shred filling e.g. the following parameters:
Label: Shred
Tooltip: Shred utility to securely erase files
Icon: gtk-dialog-warning
Path: shred
Parameters: -f -u -v -z %M
Filenames: *
Mimetypes: */*
Appears if selection contains: Both
Be sure to check the box “Appears if selection has multiple files or folders“
To finish your configuration, do not forget to open again a Terminal and type:
nautilus -q
nautilus
Recovering deleted files from USB disks on Ubuntu
Everyday we use USB keys to transfer data without transmitting them through the t. The USB keys and portable disks are small, light and their data capacity allow us to move in privacy huge files. This idyll sometimes is broken by a fatal mistake: we unintentionally delete an important file. Normally, if we are smart we recover the erased file in the Trash but in other situations when we realize the mistake we had made is too late.
In this circumstances is very import to stop to use our USB key or portable disk till we are able to use a good software for data recovering. On Ubuntu you have a wise number of dedicated software that can do this job for you, the most powerful run on Terminal as testdisk, foremost, and scalpel but you can also use a “minimal GUI” software as PhotoRec.
PhotoRec is very intuitive to use and it is able to recover many data formats from jpeg to db. After you install it using Synaptic Package Manager or the Software Center you can launch it in Terminal with:
sudo photorec
Immediately a GUI Terminal interface appears and you have just to follow the instruct ions you visualize on your monitor.
Using the arrows and the Enter keys you have to:
1 – Choose the USB device from where you want to recover the data
2 – Select the partition table (usually Intel)
3 – Specify the partition table
4 – Select the right filesystem where the data were stored
5 – Decide if you want to try the data recovering from all the free space
6 – select the directory where you want to store the recovered data. IMPORTANT: do not store the recovered data on the same USB key you are scanning for recovering
7 – Wait till PhotoRec finishes the recover operations.
PhotoRec is fast and, during our tests, we were able to recover almost the 100% of data. Not bad!!!
How to Boot Ubuntu from USB
When it comes to the most recent generation of computers, there is an option to start an operating system right from a USB stick, without an actual installation process. This may be an option to use or test a different operating system without affecting in any way the one that is already installed.
Starting from version 8.10, Ubuntu can be installed on a USB stick in a more easy way by every single user, regardless of their knowledge in Linux. To perform the installation, the user must have a version of 8.10 or later on CD and a USB stick with a capacity of at least 700 MB free space available, but this can vary according to the version of Ubuntu that you want to use for this process.
To install Ubuntu on the USB stick, you can simply boot the Live CD mode of Ubuntu or alternatively, if already installed on your on your system, you can follow the following simple procedure to do this, which is described in some basic steps below.
First of all, you need to access the Ubuntu menu bar, via System> Administration, choose Create a USB startup disk.
At this point, you will be asked to specify the source disk image of Ubuntu. If you have the Ubuntu CD in optical drive, it should appear in the list and will be selected. Otherwise, click Other and specify the location of the image. The .iso format will do it, but other versions may work as well.
When completed, you can use the stick on any computer that can boot from such units. Just tell the computer’s BIOS to use this option and restart the respective machine. The same procedure can be applied for the any distribution of Linux, so this is a helpful tutorial for everyone.
System Recovery Tools: a possible cross-platform approach through open source and proprietary solutions
The following system recovery tools will be useful to you if you are facing problem of data loss or if your system is simply crashing. It is advisable to burn copies of these tools much before any disaster strikes.
Open Source and Free approach:
G4L aka Ghost for Linux is one of the system recovery tools that is mainly a cloning and hard disk and partition imaging tool. This tool is similar to “Norton Ghost”. The images created are compressed optionally and transferred to a FTP server instead of opting for cloning locally. Ideally, of the several tools described above it is advisable to use the most suitable tool for your needs. The tool that will be most useful during a crisis like a crash or server failure will be a better tool.
The Ultimate Boot CD is one of the system recovery tools which will be very helpful when you want to run CDRom-based diagnostic tools thereby consolidating as many diagnostic tools into one bootable CD as possible. Since you can now boot from USB memory devices a script you can run “Ultimate Boot CD” from USB memory stick and a script on the script on the CD will enable you to boot newer systems from your USB sticks. This is many steps ahead than many of the other recovery tools. Moreover it gives you the flexibility of booting your system with a USB memory stick.
Knoppix is one of the system recovery tools which is essentially a bootable CD with GNU/Linux software. It ensures automatic detection of hardware and supports a wide range of devices like sound cards, most of the graphic cards, USB and SCSI devices and other peripherals. It can be used as an educational CD, a Linux demo or for system recovery purposes. Alternatively it can be used as a commercial platform for software demos. There is no need to install anything on the hard-disk as the CD is capable of storing 2GB of software installed in it. Thus this tool is a truly multi-purpose recovery tool.
Proprietary solutions:
O&O Disk recovery: This software tool scans every portion of your hard-disk, digital camera or memory card for lost files. It is so effective and reliable that it is possible to reconstruct data even when files systems have been destroyed or formatted. More than 350 types of files like music formats, word documents, movie, graphics, Excel workbooks, photo and access databases can be recognized, reconstructed and restored.
SuperDuper is one of the system recovery tools makes recovery effortless as it creates a completely bootable backup effortlessly. The strengths of this software are that it is user-friendly, easy to use with a built-in scheduler that it makes backup automatically. Moreover it performs well independent of the processor that is both on Power PC Macs as well as Intel PCs. It is particularly useful when your software application with the latest update is not working or when your hard drive begins to make noise. It is also very handy when you want to restore a stable copy of your system though you do not want t lose your existing system files or cases like this. 
