How to Update the Hosts File on a Mac Using Terminal

The hosts file allows you to map specific domain names to IP addresses, which can be useful for testing or blocking certain websites. Below is a step-by-step guide on how to update the hosts file on a Mac using the Terminal.

Step 1: Open the Terminal

1. Launch Terminal: Open the Terminal application by going to Finder > Applications > Utilities > Terminal.
   • Alternatively, open Spotlight by pressing Command + Space, type Terminal, and hit Enter.

Step 2: Open the Hosts File in a Text Editor

In the Terminal window, type the following command to open the hosts file in the Nano text editor:

sudo nano /etc/hosts

• Explanation:
  • sudo grants you superuser privileges needed to edit system files.
  • nano is a simple command-line text editor.
  • /etc/hosts is the path to the hosts file on a Mac.
• Note: You will be prompted to enter your administrator password. Type it in and press Enter (the password won’t be visible as you type for security reasons).

Step 3: Edit the Hosts File

Once you’re in the Nano editor, you’ll see the contents of the hosts file. It may look something like this:

##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting. Do not change this entry.
##
127.0.0.1       localhost
255.255.255.255 broadcasthost
::1             localhost

To add a new entry, scroll to the end of the file using the arrow keys and enter your custom mapping in the following format:

[IP Address]   [Domain Name]

Example:

If you want example.com to point to 192.168.1.1, you would add:

192.168.1.1    example.com

You can add multiple mappings if needed:

192.168.1.1    example.com
192.168.1.2    test.com

Step 4: Save Your Changes

To save your changes in Nano:

1. Press Control + O (the letter “O” for output).
2. You’ll be prompted to confirm the file name. Press Enter to save without changing the file name.
3. Press Control + X to exit Nano.

Step 5: Flush the DNS Cache

For the changes to take effect, you need to flush the DNS cache on your Mac. In the Terminal, type the following command:

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Explanation:

• This command clears the DNS cache, ensuring your system recognizes the new hosts file entries immediately.

Step 6: Test Your Changes

You can test if the hosts file update was successful by trying to ping the domain name you modified.

1. In Terminal, type:

   ping example.com

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2. The output should show that example.com is being resolved to the IP address you specified in the hosts file.

   Example Output:

   PING example.com (192.168.1.1): 56 data bytes
   64 bytes from 192.168.1.1: icmp_seq=0 ttl=64 time=0.036 ms

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Reverting Changes (Optional)

If you need to remove or modify an entry, simply repeat Steps 1 to 4, delete or edit the line in the hosts file, and save your changes.

Suggested Screenshots

While performing each step, it’s helpful to have screenshots to guide users visually. Here are some suggested screenshots:

1. Opening Terminal: Screenshot showing Terminal in Finder or Spotlight search.
2. Opening Hosts File with Nano: Screenshot of the Terminal with sudo nano /etc/hosts typed.
3. Editing the Hosts File: Screenshot of the Nano editor showing the hosts file with sample entries added.
4. Flushing the DNS Cache: Screenshot of the Terminal with the DNS flush command typed.
5. Testing with Ping: Screenshot showing the ping command with the output resolving to the modified IP address.

By following these steps, you can easily update the hosts file on your Mac. Just remember to proceed with caution, as improper changes to system files can affect your computer’s networking behavior.