iphone 升级 出现 This device isn't eligible for the requested build 解决方法

升级iturns 到10.5 之后,我的3gs 提示有更新,要更新到5.0.1 .但是当我更新时 发现更新不了,报错:This device isn't eligible for the requested build。

恢复到以前的备份也不行,我的手机越狱了.在网上着了下,终于解决了.
方法:
mac 环境!!!
1. 打开Terminal,su admin ,su root 都要输入密码的
2. vi /private/etc/hosts
3.找最后一行 看有没有  gs.apple.com 这个
4.有的话注释点 ,在前面加个 #
5. 保存,用iturns 升级手机就可以了
vi 怎么使用我就不说了.和这个文章没有什么关系
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更简单确定有没有的方法就是:
用浏览器访问:http://gs.apple.com
如果了一个可访问的页面,就说名hosts文件里面有
如果是404 告诉你页面不存在,就说名没有
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以下是在一个英文网站上着的:
Thankfully the solution is simple and falls into one of two areas:

The iOS version that’s been downloaded isn’t the right one for the device.
There’s an entry in your host file redirecting Apple traffic to another location.
In most cases, it’ll be the second option. As a quick test on the machine where you’re trying to do a restore put the following into a web browser http://gs.apple.com If an Apple 404 page (page not found) is displayed then you should be good to restore and therefore you should re-download the required firmware, reboot both your computer and the iPhone and try again. If an index page is displayed (like displayed below) then it means you’ve got entries in your host file you need to remove.

The process for removal on Mac and Windows machines is slightly different but we’ve detailed them below:

Mac OS X

1. On your Mac, open your Applications folder.

2. Navigate to the Utilities folder.

3. Open Terminal.

4. Type “sudo nano /etc/hosts” (without quotes) and press enter.

5. Enter your password

6. Use the down arrow key to find the gs.apple.com entries. Once the cursor is in front, make sure you comment out the line(s) by entering # in front of the text.

7. Save the file by pressing CONTROL+O.

8. Exit the nano editor by pressing CONTROL+X.

9. Restore your iDevice.

Windows

1. Press Start, then Programs, then Accessories

2. Launch Notepad or WordPad

3. Click Open from File menu.

4. Browse to Windows/System32/drivers/etc

5. In “files of type:” select all documents

6. Open “hosts”

7. Delete all line that have gs.apple.com or similar

8. Hit Save

9. Restore your device

You should now be sorted and up and running! Please feel free to share your experiences in the comments section below.