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Make sure you have a clipboard-aware Vim build. I recommend MacVim.
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Install or update XQuartz.app and start it.
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In the Preferences window, activate clipboard synchronization.
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Quit XQuartz.app.
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In iTerm.app or Terminal.app, connect to your remote machine with:
$ ssh -X username@hostand see the XQuartz.app icon pop-up in your Dock.
 
From now on, XQuartz.app will start automatically in the background when you use the -X flag, taking care of the clipboard synchronization for you.
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If you don't already have it, install GVim. On Debian-based systems, use:
$ sudo apt-get install vim-gtkThe idea is not to use Gvim but installing it gets you everything you need to get clipboard sharing to work:
- a minimal X
 - a Vim built with clipboard support
 
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In Vim, synchronize the unnamed and clipboard registers by adding this line to
~/.vimrc:set clipboard^=unnamed 
@MagnusBrzenk Does it still work now? In my case, it works after I reinstall XQuartz. But after I exit server and close XQuartz, it doesn't work again next time I log into the server.