Alex Ruben
How To Restart the Service After Modifying /Etc/Hosts on Linux and Ubuntu
Editing the /etc/hosts file sounds simple enough, but sometimes changes don’t show up immediately. Especially when you’re testing local hostname mappings, it’s frustrating to find out that your browser or terminal still resolves to the old address. The goal here is to figure out if you can make your updates take effect *without* rebooting the entire machine. Most of the time, Ubuntu reads the /etc/hosts file dynamically, but some apps or services might cache DNS or hostname info, making things tricky. So, understanding how hostname resolution works and how to refresh it can save a lot of headaches.
How to Fix /etc/hosts Changes on Ubuntu Without Rebooting
Modify the /etc/hosts File
First, you need to edit that file. Open up the terminal and use a trusted text editor. Typically, nano works fine, but you might prefer vim or even a graphical editor. Just run:
sudo nano /etc/hostsOnce open, add or change entries to map hostnames to IP addresses, like:
127.0.0.1 MyTest.localBe careful with formatting. It’s a plain text file, and a typo or extra space can cause resolution issues. Save your changes (in nano, press Ctrl + X, then Y to confirm, and hit Enter). It’s kind of weird, but that’s all it takes for most local processes to recognize the new entries.
When do you actually need to restart something?
In an ideal world, modifications to /etc/hosts are instant — this file is read each time the system resolves hostnames. But not all applications behave the same. Browsers, Docker containers, or local servers sometimes cache DNS info or hostname data, so you might see your old hostname resolution even after editing. Typically, if your system isn’t showing the change immediately, it’s because some app or service is caching this info and needs a refresh.
Restarting apps or services that cache hostname info can help
If your changes aren’t visible, restarting the application that’s using the hostname is the first step. For example, if you’re testing local web servers, restart your browser, or if you’ve got a local dev environment, just restart that. For command-line tools, sometimes closing and reopening the terminal helps. On some setups, the DNS cache might be causing issues, which is why you might want to restart related services.
Reload network configurations — but only if necessary
Sometimes, you might think about restarting network services, but on Ubuntu, it’s not always needed. However, if things still seem off and you’re not seeing updates, you can try restarting the NetworkManager service. It’s pretty straightforward:
sudo systemctl restart NetworkManagerThis is usually enough to refresh network state without rebooting entirely. On older Ubuntu versions, the command was:
sudo service networking restartRemember, this step isn’t always required, and sometimes it can cause temporary network hiccups, so use it with caution.
Test the updates with ping or other tools
The best way to confirm if your changes worked is to ping the hostname or run a DNS lookup. For example:
ping MyTest.localIf you see the IP address you mapped (like 127.0.0.1), that means it’s working. If not, double-check the /etc/hosts entries for typos or formatting errors. Also, ensure no other DNS caching layers obscure the results. Sometimes, browsers or OS-level DNS caches may still hold old info, so in those cases, restarting the app or even flushing DNS cache might be needed.
Extra Tips & Troubleshooting
Here are some quick tips I learned the hard way:
- Backup your /etc/hosts before editing, just in case.
- Make sure your entries are correctly formatted — no extra spaces or tabs.
- If you’re running custom DNS cache services (like dnsmasq or avahi), consider restarting or reloading their configs.
- On some setups, the nscd daemon (Name Service Cache Daemon) might be caching hostname info. Restart it with:
sudo systemctl restart nscd
Wrap-up
All in all, modifying /etc/hosts doesn’t usually require a reboot. Usually, a quick restart of the app or a service refresh does the trick. It’s kind of a “wait and see” game because some apps hold onto cached DNS info longer than expected. Knowing how to reload or restart just the necessary parts helps keep things running smoothly without the full shutdown. And honestly, once you get comfortable with this, testing hostname changes becomes way less painful.
Summary
- Edited
/etc/hostsusing sudo nano /etc/hosts - Changes take effect immediately for most system processes
- Restart hardware-dependent apps or services if changes aren’t visible
- Use sudo systemctl restart NetworkManager when needed
- Test with
pingor other network tools to confirm
Final thoughts
Hopefully this shaves off a few hours for someone. It’s not always straightforward, especially with cached DNS, but a little knowledge about what to restart can save a lot of headaches. Good luck fiddling with your hosts file and making everything work as it should.