journalctl Command Examples in Linux¶

Introduction¶

These examples show practical ways to use journalctl on a Linux terminal. Each example is written so you can adapt it for administration or troubleshooting.

Example 1: Basic Usage¶

journalctl -n 50

This is the simplest form of the command and is a good starting point before adding options.

Example 2: Common Admin Task¶

journalctl -u sshd

This example reflects a common task on RHEL, Rocky Linux, AlmaLinux, or similar systems.

Example 3: Useful Option¶

journalctl -u sshd -f

This option helps narrow the result, change behavior, or handle a more realistic target.

Example 4: Real-World Scenario¶

journalctl --since "1 hour ago"

Use this pattern when the task moves beyond a single basic command.

Example 5: Verification¶

journalctl --disk-usage

Example output:

Archived and active journals take up 256.0M in the file system.

Common Mistakes¶

• Reading the entire journal when a unit or time filter would be clearer.
• Forgetting -b when you only care about the current boot.
• Assuming persistent journals are enabled on every minimal installation.

Quick Reference¶

journalctl -n 50
journalctl -u sshd
journalctl -u sshd -f
journalctl --since "1 hour ago"
journalctl --disk-usage

Related Guides¶

• What is journalctl?
• journalctl follow logs explained
• journalctl Filter by Service and Time
• journalctl interview questions

Summary¶

Good journalctl usage means choosing the right option, keeping the target clear, and verifying the result with output you can explain.