Changing the Hostname on Ubuntu (Linux)
This guide explains how to change the hostname on Ubuntu using hostnamectl, verify the result, update /etc/hosts, and avoid common pitfalls in multi-node environments.
Environment: Ubuntu 20.04 / 22.04 / 24.04 (Server or Desktop)
[01] Check the Current Hostname
Before making any change, confirm the active hostname so you have a baseline to compare against.
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hostname
Sample output:
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root@gmaster:~# hostname
gmaster
You can also use hostnamectl for a richer status view:
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hostnamectl status
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Static hostname: gmaster
Icon name: computer-server
Chassis: server
Machine ID: e2f4a1...
Boot ID: 7d9bc3...
Operating System: Ubuntu 22.04.4 LTS
Kernel: Linux 5.15.0-107-generic
Architecture: x86-64
| Field | Meaning |
|---|---|
| Static hostname | The persistent name stored in /etc/hostname
|
| Transient hostname | The kernel’s current name (usually matches static) |
| Pretty hostname | A free-form display label (optional) |
[02] Change the Hostname
hostnamectl set-hostname writes to /etc/hostname and updates the running kernel name atomically — no reboot required.
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sudo hostnamectl set-hostname <new-hostname>
Example — renaming gmaster to gworker01:
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sudo hostnamectl set-hostname gworker01
Verify immediately without logging out:
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hostname
# gworker01
hostnamectl status | grep "Static hostname"
# Static hostname: gworker01
The prompt still shows the old name until you open a new shell session. Close and reopen the terminal (or run exec bash) to see the updated prompt.
[03] Update /etc/hosts
hostnamectl updates /etc/hostname but does not touch /etc/hosts. If the old hostname appears in /etc/hosts (which is common), update it to avoid DNS resolution warnings and to keep sudo from printing unable to resolve host.
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sudo nano /etc/hosts
Change the line that maps 127.0.1.1 (or 127.0.0.1) to the old hostname:
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# Before
127.0.1.1 gmaster
# After
127.0.1.1 gworker01
Test resolution:
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ping -c 1 gworker01
# PING gworker01 (127.0.1.1): 56 data bytes
[04] Hostname Naming Rules
Not all strings are valid hostnames. Follow these rules to avoid subtle networking issues.
| Rule | Good example | Bad example |
|---|---|---|
| Letters, digits, hyphens only | web-node-01 |
web_node_01 (underscore not valid) |
| Must not start or end with a hyphen | node-01 |
-node01 |
| Maximum 63 characters per label | gworker01 |
64+ chars |
| Case-insensitive (use lowercase) | gworker01 |
GWorker01 |
Hostnames with underscores can cause issues with some SSL/TLS libraries and Kubernetes node naming. Stick to hyphens.
[05] Multi-Node Tip — Scripted Rename
When setting up a cluster (e.g., Kubernetes, Hadoop), you often rename several machines in sequence. A small loop on the orchestrator makes this safe and repeatable:
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# Run on each worker node via SSH
for i in 01 02 03; do
ssh root@192.168.1.1${i} "hostnamectl set-hostname gworker${i}"
done
Also update /etc/hosts on every node (or use a DNS server) so all nodes can resolve each other by hostname:
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# /etc/hosts on every node
192.168.1.100 gmaster
192.168.1.101 gworker01
192.168.1.102 gworker02
192.168.1.103 gworker03
