从几个月前的14.10 daily 版本就有U盘刻录无法启动的现象，相关bug可参见：
https://bugs.launchpad.net/ubunt ... reator/+bug/1325801
系统镜像本身没有任何问题，刻录光盘、dd到U盘启动都是正常的。此问题是由于ubuntu使用了最新的syslinux版本，而大多U盘刻录软件还未支持最新的syslinux版本导致u盘无法启动，现在ubuntu系统自带及部分刻录工具是已经支持最新ubuntu14.10的U盘刻录。
通常遇到问题的都是windows用户，请更新或使用推荐的刻录软件制作U盘启动盘，具体如下：
- linux的用mkusb
- windows的用Win32DiskImager 来制作U盘启动
具体用法：
https://wiki.ubuntu.com/Win32DiskImager/iso2usb
https://help.ubuntu.com/community/mkusb
https://wiki.ubuntu.com/Win32DiskImager/iso2usb
iso2usb
目录
Return to the main Win32DiskImager page
Win32DiskImager makes an Ubuntu family USB boot drive in Windows
Introduction
A version with screenshots is published now, because it is needed ...
[This is the situation now with the new Ubuntu 14.10 version] Win32DiskImager is particularly good for pre-release testing and new releases, when the standard tools like Unetbootin might not be ready (if the configuration of the booting has been changed since the previous release).
It is possible and easy to copy/flash/clone an ISO file to a mass storage device, typically a USB pendrive. The method under the hood is the same as is described in the wiki page about mkusb.
I (sudodus alias Nio Wiklund) have tested this method and it works in Windows XP, Windows 8 and Windows Technical Preview (alias 'Windows 10'). I have not tested in Vista and Windows 7, but I am almost sure that it works in those versions too. The following screenshots were made in Windows Technical Preview.
Graphical user interface tools in Windows
Download an Ubuntu ISO file
Download an ISO file with standard Ubuntu or one of the many Ubuntu flavours, Kubuntu, Lubuntu, Xubuntu, Ubuntu Gnome ... using your web browser or download a torrent file and get the iso file faster that way.
Download and install Win32DiskImager and md5summer
Download the following help programs
http://www.md5summer.org http://sourceforge.net/projects/win32diskimager
Check the md5sums versus the lists at
https://help.ubuntu.com/community/UbuntuHashes
Install the programs and run them (which is straight-forward in Windows).
Screenshots and comments
Start and overview
md5summer
The window at the top left corner MD5sums: Generating... is the md5summer window. It helps, but is not necessary.
Ignore this warning
There can be a warning, that you need to format the disk in drive ... (at 1)
This is because Windows might not recognize the file system on the pendrive. But do not worry! The process to copy/flash/clone the iso file will overwrite the drive anyway, so it is completely meaningless to format it. One the other hand, if you want to re-use the pendrive after installing Ubuntu, then you might want to wipe the first megabyte with mkusb and then format it with gparted.
Select file
Select the ISO file that you want to use in the Win32 Disk Imager window. Click on the symbol, and get the file selector (in the right bottom corner). The default is to show image (IMG) files. ISO files are a special kind of 'synthetic image files'. They will be displayed when you select all kinds of files *.* (at 2).
Check device and Write
You can tick the box at the MD5 hash and check that it matches the value from Ubuntuhashes (instead of using md5summer).
WARNING
Check very carefully, that the device (F: in the picture) is really the USB pendrive, that you want to use. The best method is to have only the intended target USB drive connected to avoid the risk to overwrite a USB hard disk drive with all the family pictures and video clips !!!
Write
When you are sure, you can click on the Write button to start the process.
Confirm overwrite alias Final Warning
Progress view
This demo uses a Sandisk Cruzer Blade 4 GB as target drive. It is slow (5 MB/s) but reliable for booting. A USB 3 pendrive in a USB 2 port can be 6 times faster due to faster flash memory. See this link.
Work done :-) Remember to eject the pendrive safely
It is important to flush the buffers, to finish writing before pulling the pendrive. This is done with 'Eject safely'. It is also done at a correct shutdown or reboot.
Good luck and welcome to the linux world!
Links
You find more information at the following wiki page (and links from it)
https://help.ubuntu.com/community/Installation/FromUSBStick
.