If you’re trying to start SSH on Ubuntu and encounter this error:
sshd: no hostkeys available -- exiting.
Don’t worry — this is a common issue, especially when working with cloned virtual machines or golden images.
In this guide, we’ll break down:
- ✅ What this error means
- 🔍 Why it happens
- ⚙️ Step-by-step fix
- 🧠 Best practices for future
🚨 What Does This Error Mean?
SSH (Secure Shell) requires host keys to identify the server securely.
These keys are stored in:
/etc/ssh/ssh_host_*
If these keys are missing, SSH cannot start — resulting in:
sshd: no hostkeys available -- exiting.
🔍 Why This Happens
This issue typically occurs in these scenarios:
🧩 1. Cloned Virtual Machines
When you clone a VM, you may remove host keys intentionally to avoid duplication.
🧹 2. Golden Image Preparation
During template creation, admins often delete SSH keys for security reasons.
⚠️ 3. Manual Deletion or Misconfiguration
Accidental removal of /etc/ssh/ssh_host_* files.
⚙️ Step-by-Step Fix
🔹 Step 1: Generate New Host Keys
Run the following command:
sudo ssh-keygen -A
This will generate all required SSH host keys automatically.
🔹 Step 2: Restart SSH Service
sudo systemctl restart ssh
🔹 Step 3: Verify SSH Status
sudo systemctl status ssh
You should now see:
active (running)
🔹 Step 4: Confirm SSH is Listening
ss -tulnp | grep :22
If everything is working, SSH should be listening on port 22.
🔐 Test SSH Connection
From your host machine:
ssh username@your-ip-address
Example:
ssh shashwat@192.168.59.18
🧠 Best Practices (Important)
If you’re working with VMs, templates, or automation:
✅ Always regenerate SSH keys after cloning
sudo ssh-keygen -A
✅ Use cloud-init (Advanced)
Automate:
- Hostname
- SSH keys
- Network config
✅ Never reuse SSH host keys across machines
This can lead to:
- Security risks
- SSH warnings
- Connection issues
🎯 Summary
| Issue | Fix |
|---|---|
| SSH not starting | Generate host keys |
| Error: no hostkeys available | sudo ssh-keygen -A |
| Service failing | Restart SSH |
