Troubleshooting Common System Issues

Introduction

Troubleshooting systems is an essential skill for IT professionals, enabling them to quickly identify and resolve issues, ensuring smooth and uninterrupted operations.
Mastering the art of troubleshooting can transform you into a problem-solving hero, capable of navigating the complexities of modern technology with confidence and precision.

The Troubleshooting Mindset

• Remain Calm – Trying to resolve an issue while in the wrong mindset can cause more problems. Take a deep breath.
• Gather Information – Review information provided and attempt to reproduce the issue. Then try to gather new and additional information.
• Hypothesize – Using the information gathered, take your best guess at the issue and then look for supporting evidence.
• Fix – Attempt to fix the issue and then confirm the issue has been resolved by trying to reproduce the problem once more. If it doesn’t work, circle back again. Gather more information, hypothesize and fix.

Gathering System Information

uptime – System uptime, number of users logged in & load average in 1, 5 and 15-minutes increments
df – Disk Space Usage Information – filesystems, available space, percentage of used space and location of filesystem mounts.
free – Free and used memory and swap settings and usage. -m (megabytes), -g (gigabytes), -h (human readable format).
lsof – How many files we have open compared to our open file limits. The lsof command displays a list of open files. To gain a count of this, we can pipe ( | ) the results to the word count command (wc) and count by lines (-l). e.g. lsof -u admin | wc -l
top – List of running processes updated live.
ss– Dumps sockets statistics. ss -lpt (Provides us with a list of listening tcp processes; -l listening, -p process, -t tcp). If we were troubleshooting, we would be looking for a missing connection. For example a service which is supposed to be listening for TCP connections. Or one that is suspicious in nature.
ps – Displays process information. ps aux – all server running processes for all users and others that are not attached to a tty .