查看“FC21HowToISO2USB”的源代码

Creating a bootable USB drive is relatively simple yet comes in very handy, not only for showing someone Ubuntu running from the USB stick, and for troubleshooting, but also for testing hardware. Imagine you're at your local computer retailer, and you wonder if that expensive machine will run Ubuntu before you purchase it. Ask if you can use your USB stick in it. If they say no, they've lost a sale, and you've saved money.

First, I need a USB stick. For installing Ubuntu it must be at least 1Gb. I also need an ISO file of Ubuntu. I have two choices here: pick the standard installer version with a graphical user interface (GUI), or use the alternate text-based installer, which is excellent for installing on low spec machines. For now, I'll go with the standard installer, but it's the exact same process for the alternate installer.

So I have the ISO file on my computer, but I need to prepare the USB stick. For this I need Gparted. You can either open your package manager, and search for the gparted package, or use the command:

'''sudo apt-get install gparted'''

Gparted is installed under System > Administration > Partition Editor.
[Image:http://fullcirclemagazine.org/docs/uploads/FCM21-gparted.png]
Above is Gparted showing my current list of drives. What we need to do, in Gparted, is to format the USB stick and make it bootable. Making it bootable is the most important part. WARNING: we are about to completely erase the USB stick, so if you have anything valuable on it, you must back it up now.

Once the USB stick is inserted, go to the menu and choose Gparted > Refresh Devices. On its list of drives, Gparted now shows my 1Gb USB as /dev/sdd at 980.33MiB.
[Image:http://fullcirclemagazine.org/docs/uploads/gpartedusb.png]
In the above image, you'll see that it has 480Mb used. So, it needs formatting. But before we can format, we need to unmount the drive. Right click on the drive name (and info) and choose 'unmount'.
[Image:http://fullcirclemagazine.org/docs/uploads/gparted-unmount.png]
Next, we format the USB by, again, right clicking on the drive name and, from the menu, choosing Format To > FAT32 (you can, if you wish, choose FAT16 for more compatibility).
[Image:http://fullcirclemagazine.org/docs/uploads/gparted-fat32.png]
You'll see a new panel at the bottom of the Gparted screen. Here you can queue up actions, then have them run sequentially. We need only to format, so right click in that new panel and choose 'Apply all Operations'. You will be asked if you are sure you want to apply this operation, click 'Apply'.
[Image:http://fullcirclemagazine.org/docs/uploads/gparted-format.png]
Your USB stick is now blank, but is it bootable? Let's find out. Right click on the drive name in Gparted and, from the menu, choose 'Manage Flags'.
[Image:http://fullcirclemagazine.org/docs/uploads/gparted-flags.png]
In my case, my USB is bootable, shown by the ticked box beside 'boot'. Needless to say, if this box is not ticked, now is the time to tick it, and click 'Close'. So now the USB stick is ready for Ubuntu. Pull out your USB stick, and reinsert it to remount it, ready for later.

But how to get Ubuntu into the USB stick? Unetbootin. This GUI application will copy the files within an ISO file to the USB stick. You can download the latest .deb file for Unetbootin from: http://unetbootin.sourceforge.net/unetbootin-i386-latest.deb/

Browsers, such as Firefox, will ask you if you want to save the .deb to your computer or, handily, download the file and open it in Gdebi for installing. I chose to open it in Gdebi for ease of use.
[Image:http://fullcirclemagazine.org/docs/uploads/unetbootin-ffox.png]
The file will download and the Gdebi window will open up and install Unetbootin for you. When the install is done, close Gdebi.

Unetbootin is installed under Applications > System Tools. Start Unetbootin and you will see the default screen:
[Image:http://fullcirclemagazine.org/docs/uploads/unetbootin.png]
At the top of the Unetbootin screen, you can choose to automatically download an ISO from the list, but we already have the ISO, so click the round icon beside 'Diskimage', then click the '...' button to select the ISO file. The only other thing you need to check is that your USB drive is selected at the bottom of the window. In this case, it says /dev/sdd1, which is my USB stick, so I'm ready to go. Clicking 'OK' begins the copying process.
[Image:http://fullcirclemagazine.org/docs/uploads/unetbootin-copying.png]
On my system - which is pretty fast - Unetbootin pauses for quite a few minutes at 4%. Don't worry if this happens. Remember, your system needs to copy nearly 1Gb of files through the USB.
[Image:http://fullcirclemagazine.org/docs/uploads/unetbootin-done.png]
You can either click 'Reboot Now' to test your new bootable USB stick on the current machine, or click 'Exit' to close Unetbootin. Remember to check that your USB stick is properly unmounted before you remove it from the PC.

PLEASE NOTE: To boot a PC from a USB device, you may have to access the BIOS settings of the PC, to ensure that the first bootable device is the USB - and not the CD/DVD, floppy, nor hard drive; the second bootable device should be the hard drive. Most BIOSes use the Del key (on the keypad, not the Delete key on the keyboard) to access the BIOS settings; some use the F1 or F2 keys. This key press must be done within a few seconds of powering on the machine. When no further USB booting is required, remember to reset the Boot-Sequence back to the hard drive (only).

NEXT MONTH: How to install an Ubuntu distro to your ASUS EEE PC using a bootable USB stick. 
==参看==
*[[FC第21期内容索引]]
*[[FC:Work]]

[[Category:FCHowTo]]
[[Category:FC第21期]]