You run ssh user@host but get the error: ssh: Could not resolve hostname host: Name or service not known. What is the likely cause?

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Linux CLI - SSH and Remote Access

You run ssh user@host but get the error: ssh: Could not resolve hostname host: Name or service not known. What is the likely cause?

AThe SSH service is not running on the remote server.

BThe hostname 'host' is not defined in DNS or /etc/hosts.

CThe user 'user' does not exist on the remote server.

DThe SSH client version is outdated.

Step-by-Step Solution

Solution:

Step 1: Analyze error message
Error says hostname cannot be resolved, meaning DNS or hosts file lookup failed.
Step 2: Identify cause
Hostname 'host' is unknown to the system, so connection cannot start.
Final Answer:
The hostname 'host' is not defined in DNS or /etc/hosts. -> Option B
Quick Check:
Hostname resolution failure = The hostname 'host' is not defined in DNS or /etc/hosts. [OK]

Quick Trick: Check hostname spelling and DNS or hosts file [OK]

Common Mistakes:

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