

For Ubuntu 12.04 Precise and Elementary OS Luna, you can install this icons by running below 3 commands one by one in terminal (Ctrl+Alt+T):
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sudo add-apt-repository ppa:elementary-br/projects
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sudo apt-get update
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sudo apt-get install ieos7-icons
For other Ubuntu editions, directly download and install the ieos7-icons DEB package from launchpad.net
Once installed, use Unity Tweak Tool, Gnome Tweak Tool or other system tools to apply the theme.
Enjoy!
Source : http://ubuntuhandbook.org/index.php/2013/09/ios-7-style-icons-theme-for-ubuntu-elementary-os/