Ceci est une ancienne révision du document !
Many years back, when USB pendrives of over 4 GBytes started to become commonplace, I did an experiment in Linux systems administration with a class of future computer science engineers, that consisted of using such drives as the basis of a full-blown Ubuntu installation. Yes, back then 4 GBytes was sufficient to hold the system itself - at about 2.2 GBytes - with some space available for user documents. That experiment was somewhat of a success, though it was immediately apparent that drive speeds were a limiting factor that precluded actually using such equipment in a production system. The then-current USB 2 had speeds at about 48 MBytes/s, though the characteristics of the Flash-based drives themselves brought that down to the 20-22 MBytes/s range - obviously much lower than the 100-120 MBytes/s that could be expected from an internal (spinning platter) hard drive.
Forward to year 2015, and modern pendrives are offering much larger capacities at lower prices. Some models are also available with USB 3 connections. The advertised useful speeds of the 32 GByte Sandisk model used in this test go all the way up to 130 MBytes/s, comparable to a laptop’s internal platter hard disk drive. It can be noted that these speeds are still much lower than USB 3’s theoretical 500 MBytes/s maximum speed, so the Flash technology used in the drive still seems to be the limiting factor. This part cost me 18 EUR (about 20 USD or 13.30 GBP).
To install the system, I chose to try out Elementary OS stable version 0.3.1 for the AMD 64-bit architecture. This is a relatively light derivative of Ubuntu Trusty (14.04) that I had previously reviewed in FCM#77 (http://fullcirclemagazine.org/issue-77/), and Michael Davies has also examined in its beta version in FCM#91 (http://fullcirclemagazine.org/issue-91/). The distribution itself comes with the GTK 3-based Pantheon desktop manager, reminiscent of Apple OS-X. Few applications are installed by default (Midori web browser, Geary mail client, no office suite), though the standard offering is available as usual from Ubuntu’s repositories. Needless to say, other distributions based on lightweight desktop managers such as Mate, XFCE or LXDE could certainly also be considered.
INSTALLATION
The first task was to install the system on the target drive - without affecting my laptop’s regular drive. There are several ways to make sure of this. This first point is, naturally, making sure any data on the computer is fully backed up.
I then proceeded to format a second external USB pendrive (a smaller 2 GByte model) I had lying around, with the Elementary ISO image. There are several ways of doing this, such as using the official Ubuntu USB creator (http://www.ubuntu.com/download/desktop/create-a-usb-stick-on-ubuntu), the unetbootin tool, or just plain dd. This second USB drive is used only as a bootable medium to install the system, and can later be repurposed for other uses.
Noting each drive’s identification letter can be enough to make sure - exercising some care - that the installer does not overwrite existing data. In general, the internal hard drive should come up as /dev/sda, while succeeding USB drives should appear as /dev/sdb, /dev/sdc, etc. So, if we are booting off /dev/sdb, and installing to /dev/sdc, we should be good to go.
However, just to be on the safe side, I opted to simply disconnect the computer’s internal hard drive. This is relatively easy on a desktop computer, since one simply needs to disconnect a SATA cable from the hard drive. On a laptop, the entire hard drive usually needs to be removed.
What I was basically working with was a diskless computer on one hand, the 2 GByte USB bootable medium and the 32 GByte USB target drive on the other. I placed the 2 GByte drive in an ordinary USB 2 connector, and the 32 GByte in the computer’s only USB 3 connector - that can be identified by the blue plastic flange inside the connector or, on some models, by the “SS” (“Super Speed”) badging. Using an USB 3 external drive in an USB 2 connector is certainly possible, but negates the availability of the speed boost given by version 3. This is highly noticeable in practice.
The BIOS on most modern computers can be convinced to boot off a specific drive by holding down the F12 key while booting, but this depends a bit on your exact hardware. Some experimentation may be needed to get the BIOS to recognize and boot off the bootable medium USB. Actually reading the manual can at times come in handy on some models (been there, done that).
Once up and running, the Elementary live desktop environment comes up as expected. The Ubuntu-derived installer recognized the 32 GByte target drive with no problems as an available hard drive. Partitioning was performed in the usual manner. It should perhaps be noted that I immediately chose to use the entire drive for the Linux system. Using separate partitions for root and home directories on such a small drive is probably not really useful, and moreso taking into account expected usage patterns. Aside from that, the installation process was completely uneventful - yet another case of no news being good news.
USING THE NEW SYSTEM
It is clear that the main advantage of using a small drive is transportability. The drive can be slipped onto your keychain and carried around with much ease. However, it will probably never be a complete replacement for a user’s main system, which will potentially hold many GBytes of documents, music, multimedia files, etc. So this experiment became a case of deciding what precisely I wanted to use the drive for.
I basically wanted to access data related to projects I was currently working on. I usually use a combination of Dropbox and Google Drive to make these files available when away from home. Having a complete operating system of my choice with me that I can plug into and boot from on whatever computing platform is available to me, has the advantage of being able to work on the files with my own choice of software, on top of simply having the files available. This will obviously depend on each user’s specific needs, but, for me, a combination of the following works well: • Google Chrome and Dropbox, to access files from the cloud. • LibreOffice 5, mostly to work with presentations. • Thunderbird, with the Enigmail plugin to handle the encrypted and signed mail I sometimes need to use. • Some more specific stuff, such as LaTeX, to prepare scientific communications.
I have found that, in practice, all regular applications found by default in the various Ubuntu distributions work well off the USB drive. This is also true for graphical applications such as Inkscape or Gimp, in the latter case even up to image files in the 2 to 5 Mpixel range. Due to space considerations - but also disk speed - I will not be trying out applications that are known to require more processing power and speedy disks, such as the Eclipse + JBoss combination to develop Java applications, or Kdenlive to edit videos. Such extreme use cases are probably still better left to serious rigs with the appropriate drives and peripherals. Other than that, more mundane tasks such as browsing the Internet or text processing can very well be undertaken in some comfort. Putting my words into practice, so to speak, I am writing this on the USB drive itself - and not noticing much difference from using the internal hard drive.
Some computer hardware seems to interface better with USB 3 than others. At times, reading files from one device on the USB bus and writing it to another seems to run into bottlenecks. Another fact to take into account is the well-known difference in speeds when writing to a Flash-based medium, as opposed to reading from it. Actual file-write speeds have been measured in the vicinity of 15.4 MBytes/s. These speed levels are rather lower than the advertised 130 MBytes/s maximum - which is probably a best-case statement, and relative only to reading activity - but are in practice sufficient for usual workflows.
SECURITY
Carrying a certain amount of your data around on such a small drive exposes it to the typical accidents to life, such as loss or theft. Keeping your data secure acquires a new dimension on devices that are mobile by their very nature, and it is well to keep security in mind. To my mind, the very least that should be done is to encrypt users’ home directories. Luckily, this is easy to set up during the installation process, and does not seem to impact data transfer speeds in a meaningful way. However, it does mean no autologin, since the home directory is encrypted until the password is entered manually.
Going further and encrypting the entire disk may also make good sense, since that would, in principle, make installing backdoors or trojans on your drive more difficult for a potential hacker. This article in The Simple Computer (http://thesimplecomputer.info/full-disk-encryption-with-ubuntu) has a full description on the process. I would recommend giving the “The What & The Why” section a read, even if the final choice lies, as always, with you, the owner of the hardware.
Perhaps the most practical recommendation to be made here is to simply always keep the pendrive physically within your sight, and if possible on your person: no leaving it connected to a computer that is running, while you go out of the room. Booting the system up costs less than 30 seconds on my computer - including the time needed to enter the password - while shutting down costs 5 to 6 seconds. So there is really no excuse for not shutting down the computer and extracting the pendrive when needing to leave “for a minute”.
With these simple precautions in mind, using a USB drive to carry around your computing environment of choice is a way of making use of modern technology to reduce the physical stress of having to cart several kilograms of electronic equipment around all day. In the modern world, most places we go to can make a computer available to us. Working off our own drive makes it possible not only to work with our stuff on our own terms, but also to leave the computer behind us in the state we found it in, with none of our files littering the desktop and potentially risking embarrassment for ourselves and for others.