I found that post How to disable IPv6 on Ubuntu?
I need to ask about this file
/etc/default/bind9. I couldn't find this file.
Where can i find it?
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Bind is related to DNS configuration to see bind9 file in the path /etc/default/bind9
Run below command:
sudo apt-get install bind9
You can go through the link for exact steps: How to disable IPv6 in Ubuntu 14.04?