重装系统，或者在一台新电脑上重装 Dropbox 之后，如果不想 Dropbox 下载一遍所有的文件，可以使用以下的方法，让 Dropbox 同步已经存在的 Dropbox 文件夹。保证自己本地已经有一份 Dropbox 文件夹拷贝。然后执行以下操作：

  1. 假设已经存在的 Dropbox 文件夹在 E:\Dropbox
  2. 安装 Dropbox
  3. 安装完成之后，登陆，在某一界面会显示高级选项，点击高级
  4. 进入高级界面之后，可以选择将 Dropbox 放到硬盘的位置，设置自己本地的目录
  5. 因为我本地已经有了一份 Dropbox 备份，所以将 Dropbox 设置中的位置选到 E:\
  6. 因为本地已经有 Dropbox 目录，所以程序会告诉你本地已经有一份，你是否想要合并—-“There is already a folder here called Dropbox. Do you want to merge all the existing files in that folder into your Dropbox?”，选择是，即可
  7. 之后 Dropbox 就会自己比较文件差异，然后就很快的将整个文件夹同步了

解决方案来自：http://forums.dropbox.com/topic.php?id=29612

附英文版：

Just copy from your existing Dropbox folder to Dropbox folder on new machine, and do the followting step:

  1. Put the existing Dropbox folder in /home/Me/, so it will be /home/Me/Dropbox
  2. Install Dropbox and do all things it requires you to do
  3. After installation, at some point, you will be asked to choose setup type. Here you will choose “Advanced”, and “Next”
  4. Now you want to specify where to put your Dropbox folder, so tick “I want to choose where to put my Dropbox”.
  5. Since I have my existing Dropbox folder at /home/Me/Dropbox, so I change the folder to ” /home/Me/”.
  6. Since you have the Dropbox folder already in the directory, the program would say “There is already a folder here called Dropbox. Do you want to merge all the existing files in that folder into your Dropbox?”. Here we click OK, and Next.
  7. In the extended attributes, we tick “Yes, enable synching for extended file attributes (may require root password)”
  8. Next, choose whatever you want. For me I choose to synch all files inthe Dropbox folder.

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