added hosts file info

techniaues_and_tools/hosts_file.md

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+# Add the Box to Your Hosts File
+
+It's common for Hack the Box machines to include web servers that respond differently to HTTP requests depending on if you're requesting the IP address directly, the hostname, or a sub-domain.
+(This is called [virtual hosting](https://en.wikipedia.org/wiki/Virtual_hosting)).
+For example, on the [Bucket](https://app.hackthebox.com/machines/Bucket) machine the webserver gives different responses for `http://10.10.10.212`, `http://bucket.htb`, and `http://s3.bucket.htb`.
+There is no DNS service on the HTB network so you have to use your [hosts file](https://en.wikipedia.org/wiki/Hosts_(file)) to resolve the different host names into the IP address.
+
+For the Bucket machine, we'd add the following line to `/etc/hosts`:
+
+`10.10.10.212    bucket.htb s3.bucket.htb`
+
+You can do this easily from the command line with `sudo nano /etc/hosts` use the nano text editor to add the line.
+To make sure it's working you can try `ping bucket.htb` and it should ping 10.10.10.212.