commands/optimisation/optimize-boot-speed.md

You are optimizing system boot speed by identifying and remediating slow or hanging processes.

Your Task

1. Analyze boot performance using systemd-analyze:

   • systemd-analyze - Show total boot time
   • systemd-analyze blame - List services by boot time impact
   • systemd-analyze critical-chain - Show critical path bottlenecks
   • systemd-analyze plot > boot-analysis.svg - Generate visual timeline (optional)

2. Identify slow services:

   • Services taking > 5 seconds to start
   • Services in the critical boot path causing delays
   • Services with timeout issues
   • Parallel vs sequential loading issues

3. Detect hanging processes:

   • Check for services waiting on timeouts
   • Identify dependency chain bottlenecks
   • Look for failed network mounts or remote resources
   • Find services that could be started later (after boot completes)

4. Categorize optimization opportunities:

   • Disable: Unnecessary services that can be completely disabled
   • Delay: Services that can use After=network-online.target or similar
   • Parallel: Services that could start in parallel instead of sequentially
   • Configure: Services needing timeout or dependency adjustments

5. Propose specific optimizations:

   • Provide exact systemctl commands to implement changes
   • Explain the impact and safety of each change
   • Suggest configuration tweaks for slow services
   • Recommend masking vs disabling where appropriate

Key Commands

• systemd-analyze time - Overall boot time breakdown
• systemd-analyze blame - Time taken by each unit
• systemd-analyze critical-chain - Critical path analysis
• systemctl list-dependencies --before - What loads before a service
• systemctl list-dependencies --after - What loads after a service
• journalctl -b | grep -i timeout - Find timeout issues
• systemctl show <service> --property=TimeoutStartUSec - Check timeout settings

Output Format

1. Boot Performance Summary:

   • Total boot time
   • Kernel, userspace, and firmware times
   • Comparison to typical boot times

2. Top Boot Time Offenders (services > 3 seconds):

   • Service name and time taken
   • What the service does
   • Whether it's essential

3. Hanging/Timeout Issues:

   • Services with timeout problems
   • Root cause analysis
   • Recommended fixes

4. Optimization Recommendations:

   • Prioritized list of changes (high to low impact)
   • Specific commands to execute
   • Expected time savings
   • Risk assessment for each change

5. Implementation Plan:

   • Step-by-step instructions
   • Backup/rollback procedures
   • Testing recommendations

Be specific and actionable. Always explain the safety and reversibility of proposed changes.