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Patterns: How Discovery Explores a Device

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In this lesson, you will learn:

  • What a pattern is
  • Infrastructure patterns and application patterns
  • How pattern content is updated

🔁 Quick look back: Last time: How Discovery Talks to Devices: SSH, WMI, PowerShell and SNMP. You learned which protocol and port Discovery uses for each device.

1 The Problem: Discovery Must Know What to Ask

Each device type needs different questions. A Linux server needs ‘uname’ and ‘df’. A PostgreSQL database needs its own checks. Priya asks:

  • ‘How does Discovery know what to run on my servers?’
  • ‘Who decides those commands?’

🎯 The problem: Discovery must know exactly what to ask each kind of device.

👉 The fix: Patterns hold those questions. Each pattern is a recipe for one kind of device.

Five steps of the Linux Server pattern.
Figure 1. What the Linux Server pattern does on snwr-mail-01, step by step.

2 What a pattern is

A pattern is a set of steps that explores one kind of device or application. It runs commands, reads the answers and fills in the CI.

Key term: Infrastructure pattern

Explores a device, such as a Linux server, a switch or a vCenter.

Key term: Application pattern

Explores software on a server, such as PostgreSQL or IIS.

Key term: Pattern Designer

The tool where you read, debug and build patterns.

Discovery chooses the pattern after classification. A Linux server gets the Linux Server pattern.

3 Where pattern content comes from

  • ServiceNow ships hundreds of ready-made patterns.
  • Updates come through Store apps, such as Discovery and Service Mapping Patterns, and Visibility Content.
  • These updates can arrive between platform upgrades. So keep them current.

💡 Good to know: Before building your own pattern, always check whether a newer ServiceNow pattern already does the job.

4 Project Clear View: How We Implemented It

📍 Situation: Priya is worried about what Discovery will run on her servers.

🧭 Decision: Show her the real steps of the Linux Server pattern, before any scan.

🛠️ Steps we took:

  1. Opened the Linux Server pattern on snwrdev with Priya.
  2. Walked through the steps: connect, run commands, parse, fill the CI, add links.
  3. Listed the commands it runs, for her review.
  4. Explained that these commands only read data. They don’t change anything.

✅ What we verified:

  • Priya was comfortable with the commands.
  • She asked for the full list in writing, for the sudo rules.

📁 Evidence: The first list of pattern commands. It grows into the privilege matrix (see Client Prerequisites › Building the Service Account and Privilege Matrix).

5 Quick recap

  • A pattern is a set of steps that explores one kind of device or application.
  • Infrastructure patterns explore devices. Application patterns explore software.
  • Pattern updates arrive through Store apps, between upgrades.
  • Check for newer content before building your own pattern.

6 Check yourself

Think of your answer first. Then tap to check.

1 What is a pattern? Show answer

A set of steps that explores one kind of device or application and fills in its CI.

2 Which kind of pattern would explore PostgreSQL on snwr-db-01? Show answer

An application pattern.

3 How do pattern updates reach an instance? Show answer

Through Store apps, such as Discovery and Service Mapping Patterns and Visibility Content.

Nice work! You know how Discovery explores a device. 🎉
Next up: How Discovered Data Reaches the CMDB

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