Tech Notes

System Boot & Resume Diagnostics

Contents

• Overview
• Check System Boot Time
• Check Resume Events (Sleep/Wake)
• Combined Usage Notes
  • Important Note

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Overview

This note contains useful Linux commands for checking system boot time and investigating resume (sleep/wake) events using system logs.

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Check System Boot Time

Use this command to see when the system last booted:

uptime -s

What it shows:

• The exact timestamp of the last system boot
• Useful for verifying reboots or system uptime tracking

Example output:

2026-05-03 08:14:22

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Check Resume Events (Sleep/Wake)

Use this command to filter system logs for resume-related events:

journalctl --since today | grep -i "resume"

What it shows:

• Entries related to system resume from sleep/hibernate
• Helps diagnose wake-up behavior or power state transitions

You may also want to expand search for related events:

journalctl --since today | grep -Ei "resume|suspend|wake"

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Combined Usage Notes

• uptime -s tells you when the system started running
• journalctl helps you understand what happened during the session

• Together, they help diagnose:

  • unexpected reboots
  • sleep/wake issues
  • system stability problems

Important Note: If resume events are missing, it may indicate that:

• the system was fully shut down instead of suspended
• logs were rotated or cleared
• power events were not recorded by the kernel

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