To modify the hosts file of the Linux system, you need to edit it with administrator permissions. 1. The hosts file is located in the /etc/ directory, and cat /etc/hosts can be viewed; 2. Use sudo to modify it with editors such as nano/vim/gedit, and the format is the IP address and the host name; 3. After modification, it may need to clear the DNS cache or restart the NetworkManager service to take effect; 4. Pay attention to the correct format, avoid frequent modifications, and commenting indeterminate entries to operate safely.

It is actually not difficult to modify the hosts file in the Linux system, but many people will be a little hesitant when operating the first time, mainly because they are afraid that the system file will affect network access. In fact, just follow the correct method, editing hosts is a simple and practical little skill.

Find the location of the hosts file

The hosts files of Linux systems are usually placed in the /etc/ directory, and the full path is /etc/hosts . It is a plain text file that can be opened with any text editor, such as nano, vim, or gedit.

You can enter the following commands to view the hosts content of the current system through the terminal:

 cat /etc/hosts

Usually you will see something like the following:

 127.0.0.1 localhost
::1 localhost

This is the default local loopback address setting of the system.

Edit hosts with administrator permissions

Because hosts is a system-level configuration file and ordinary users do not have write permissions, they must use sudo to obtain temporary administrator permissions. For example, using the nano editor can do this:

 sudo nano /etc/hosts

If you are more used to using vim, change to:

 sudo vim /etc/hosts

You can also use gedit in a graphical interface environment:

 sudo gedit /etc/hosts

• When adding a new entry, the format is: IP address one or more spaces/tab hostname (multiple)

• For example, if you want to point a website to the local testing environment, you can add a line:

   127.0.0.1 example.test

• If you want to block a website, you can point it to 127.0.0.1:

   127.0.0.1 badsite.com

Remember to confirm that the syntax is correct before saving, do not have more spaces or fewer spaces, otherwise it may cause parsing errors.

Notes and FAQs

Not all programs will take effect immediately after editing hosts. Some applications (such as browsers) may cache DNS records, and at this time, you need to clear the cache or restart the service.

• On Ubuntu, you can try restarting NetworkManager:

   sudo systemctl restart NetworkManager

• Or use the nscd tool to clear the cache:

   sudo nscd -i hosts

  However, not all systems have nscd installed, so if you don't install it by default, you don't have to worry too much.

  Also note that:

  • Modifying hosts is only valid for this machine and does not affect other devices.
  • It is not recommended to frequently modify hosts, especially on production environment servers, as it can easily cause confusion.
  • If you are not sure about the function of a certain line, it is best not to delete it randomly. You can comment out first (add # at the beginning of the line) and try it.

  Basically that's it. Although the operation is not complicated, it is easy to ignore permissions and format details, and you can do it smoothly with a little attention.

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