這幾天要在 DigitalOcean 上面裝東西的時候，發現 apt-get update 之類的指令都非常慢，然後也注意到他試圖存取 IPv6。
因此就發了一個 Issue Ticket 給 DO 的客服，回答如下：
Hello!
Can you clarify the results you are seeing that show the connection as slow?
Just to be clear, IPv6 is not enabled in SFO droplets, so you shouldn’t be able to make any IPv6 connection from SFO.Please let us know.
Thanks,
Tyler
DigitalOcean Support
https://digitalocean.com/community
隨手找一下如何關掉 apt-get 的 IPv6，可以找到這篇
簡單說就是sudo touch /etc/apt/apt.conf.d/99force-ipv4
sudo echo "Acquire::ForceIPv4 true;" > /etc/apt/apt.conf.d/99force-ipv4
Config options Acquire::ForceIPv4 and Acquire::ForceIPv6 were added to version 0.9.7.9~exp1 (see bug 611891) which is available in Ubuntu Saucy (released in october 2013) and Debian Jessie (not released yet).
基本上這樣就完成了，如果版本不一樣的話 (not support)，可以嘗試下面其他答案。再不吝回報一下囉！
題外話，如果用 >>> DigitalOcean 這個連結註冊 DO 可以得到 $10 美金的 Credit 喔！(我可以得到 $25，來玩玩看吧！)