To add a hosts entry for local.example.gen pointing to 192.168.128.10 on a Linux system, follow these steps:

1. Open the hosts file with root privileges

Use a text editor such as nano or vim with sudo to modify /etc/hosts:

   sudo nano /etc/hosts

1. Add the entry

Append the following line to the end of the file, ensuring there is a single space between the IP address and the hostname:

   192.168.128.10    local.example.gen

1. Save and exit

• In nano, press Ctrl+O to write the changes, then Enter to confirm, followed by Ctrl+X to exit.
• In vim, press Esc, type :wq, and press Enter.

1. Verify the entry

Check that the entry was added correctly by viewing the file:

   cat /etc/hosts

Ensure the line appears exactly as added.

1. Test the mapping

Use ping or nslookup to confirm that local.example.gen resolves to the specified IP:

   ping local.example.gen

or

   nslookup local.example.gen

1. Troubleshoot if needed

• If the entry does not take effect, ensure there are no leading/trailing spaces or duplicate entries.
• Confirm the hostname is spelled correctly (e.g., local.example.gen, not local.example.gen.).
• Check for syntax errors in /etc/hosts (e.g., missing tabs or incorrect formatting).
• If changes are not reflected, flush any caching (e.g., restart networking services or flush DNS cache if applicable).

Note: The hosts file is case-sensitive for hostnames, and entries must use a single space (or tab) to separate the IP address from the hostname. Avoid adding extra spaces or characters.