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Troubleshooting: Fix Problems Systematically

Troubleshooting is systematic. Check one thing at a time. Find the problem. Fix it.

Here's the thing: Troubleshooting is a skill. Learn the approach. Use it.

The Troubleshooting Process​

1. Understand the Problem​

Ask:

  • What's broken?
  • When did it break?
  • What changed?
  • What should it do?

My take: Understand the problem first. Don't guess.

2. Reproduce the Problem​

# Try to reproduce
# See if it happens consistently

My take: Reproduce the problem. If you can't reproduce it, you can't fix it.

3. Check Logs​

# System logs
journalctl -p err --since "1 hour ago"

# Service logs
journalctl -u service-name -n 100

# Application logs
tail -f /var/log/app.log

My take: Logs tell you what's wrong. Check them first.

4. Check Status​

# Service status
systemctl status service-name

# System resources
htop
df -h

My take: Check status. See what's running. See what's using resources.

5. Isolate the Problem​

# Test components separately
# Find what works and what doesn't

My take: Isolate the problem. Narrow it down. Find the root cause.

6. Fix and Test​

# Make the fix
# Test that it works
# Verify the problem is solved

My take: Fix it. Test it. Verify it works.

Common Troubleshooting Areas​

Services Not Starting​

# Check status
systemctl status service-name

# Check logs
journalctl -u service-name -n 100

# Test manually
sudo -u service-user /path/to/command

My take: Services fail for reasons. Check status. Check logs. Test manually.

High Resource Usage​

# Check CPU
top
htop

# Check memory
free -h

# Check disk I/O
sudo iotop

# Find the process
ps aux --sort=-%cpu | head -10

My take: High usage means something is using resources. Find it. Fix it.

Network Problems​

# Check interface
ip link show

# Check IP
ip addr show

# Test connectivity
ping 8.8.8.8

# Check DNS
nslookup google.com

My take: Network problems are systematic. Check one thing at a time.

Systematic Approach​

Start Broad, Narrow Down​

  1. Check if system is running
  2. Check if service is running
  3. Check if network is working
  4. Check specific component
  5. Fix the problem

My take: Start broad. Narrow down. Find the problem.

Common Mistakes (I've Made These)​

  1. Jumping to conclusions: Don't guess. Check systematically.

  2. Not checking logs: Logs tell you everything. Check them.

  3. Changing too many things: Change one thing at a time. Test results.

  4. Not documenting: Document what you tried. Learn from it.

  5. Giving up too early: Troubleshooting takes time. Be patient.

Real-World Examples​

Service Won't Start​

# 1. Check status
systemctl status myservice

# 2. Check logs
journalctl -u myservice -n 100

# 3. Test manually
sudo -u service-user /usr/local/bin/myservice

# 4. Check permissions
ls -la /usr/local/bin/myservice

# 5. Fix and restart
sudo systemctl restart myservice

System is Slow​

# 1. Check resources
htop
df -h

# 2. Find resource hogs
ps aux --sort=-%cpu | head -10

# 3. Check I/O
sudo iotop

# 4. Fix the problem

What's Next?​

Now that you understand troubleshooting, you can fix problems systematically. Or review Logging to understand logs better.

Personal note: Troubleshooting used to frustrate me. Then I learned the systematic approach. Now I troubleshoot methodically. It works. Learn it.