Linux Troubleshooting

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Linux Troubleshooting

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Resources:

• Top 100+ Linux Interview Questions and Answers (2025) - Naukri Code 360

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How do you check disk space usage on a Linux system?

To check disk space usage, you can use the df command:

• df -h: Shows disk usage in a human-readable format (GB, MB).
• du -sh /path/to/directory: Displays disk usage for a specific directory.

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How can you troubleshoot high CPU usage on a Linux system?

Use the following tools to troubleshoot high CPU usage:

• top: Provides a real-time view of running processes and their CPU usage.
• htop: Similar to top, but with a more user-friendly interface.
• ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%cpu: Lists processes sorted by CPU usage.

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What command can you use to check for open ports and services?

Use the netstat or ss commands:

• netstat -tuln: Lists all open ports and associated services.
• ss -tuln: Shows open ports with more details and is faster than netstat.

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How do you check and free up memory on a Linux system?

• Use the free -h command to check memory usage in human-readable form.
• Use top or htop to monitor memory usage by processes.
• To free up memory, you can kill memory-intensive processes or use sync; echo 3 > /proc/sys/vm/drop_caches to drop the cache.

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How do you find large files on a Linux system that might be filling up disk space?

Use the find command to search for large files:

• find / -type f -size +1G: Finds all files larger than 1GB in size. You can adjust the path and size parameter based on your requirement.

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How can you troubleshoot a system that won’t boot?

• Check GRUB: Ensure the GRUB bootloader is loading correctly.
• Boot in recovery mode: Use recovery or rescue mode to access the system.
• Check logs: Check /var/log/syslog or /var/log/messages for error messages.
• Filesystem issues: Use fsck to check and repair filesystem corruption.

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How do you check for hardware issues on a Linux system?

• dmesg: Displays kernel ring buffer messages related to hardware and boot issues.
• lshw: Lists detailed information about the hardware components of the system.
• smartctl -a /dev/sda: Checks the health of hard drives using S.M.A.R.T. data.

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What are some ways to troubleshoot network connectivity issues in Linux?

• Check interface status: Use ifconfig or ip a to check network interfaces.
• Ping test: Use ping <hostname/IP> to check network connectivity.
• Traceroute: Use traceroute <hostname/IP> to trace the route packets take.
• DNS issues: Use nslookup or dig to troubleshoot DNS resolution problems.

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How do you check the system logs for troubleshooting purposes?

• Use the journalctl command to view the system logs:
  • journalctl -xe: Shows the most recent critical errors.
  • journalctl -u <service-name>: Views logs specific to a service.
• Alternatively, you can check the log files located in /var/log/, such as syslog, dmesg, and auth.log.

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How can you troubleshoot a slow system performance issue in Linux?

• Check CPU usage: Use top or htop to monitor processes consuming CPU.
• Check memory usage: Use free -h and vmstat to monitor memory usage.
• Check I/O performance: Use iotop or iostat to monitor disk I/O issues.
• Review logs: Check logs in /var/log/ and use dmesg for hardware-related issues.