Top Linux Command-Based Interview Questions [2025]

Linux Administration Commands

1. What command would you use to check disk usage on a Linux server?

• df -h
• Displays disk space
• Identifies full partitions
  The df command shows disk usage in a human-readable format. It helps admins identify storage issues, a core skill for maintaining Linux servers in production environments with large datasets.

2. How would you use a command to monitor real-time CPU usage?

To monitor CPU usage in real-time, use top or htop to display process details. This tracks system performance, a vital task for admins ensuring efficient Linux server operations under heavy workloads.

3. Why would you use systemctl to manage services on a Linux server?

• Controls service states
• Enables/disables services
• Checks status
  The systemctl command manages services for reliable system operations.
  It replaces older init scripts.
  This ensures consistent service management in modern Linux environments.

4. When would you use dmesg to troubleshoot a Linux server?

The dmesg command is used to view kernel logs for hardware or driver issues.

• Filters with dmesg | grep error
• Monitors real-time with dmesg -w
• Aids diagnostics, a core Linux principle

5. Where would you check system logs using a command on a Linux server?

sudo journalctl -xe

Use journalctl -xe to view detailed system logs. This identifies errors, a critical task for admins troubleshooting Linux servers in enterprise environments with complex applications.

6. Which command displays running processes on a Linux server?

The ps command with options like aux lists running processes with details.
It shows CPU and memory usage.
Admins use it to monitor system activity.
This ensures efficient resource management in production systems.

7. What command would you use to check memory usage on a Linux server?

• free -m
• Shows memory stats
• Tracks usage trends
  The free command displays memory usage in megabytes.
  It helps identify leaks.
  This is vital for maintaining Linux server performance.

8. How would you use a command to update packages on a Linux server?

sudo apt update && sudo apt upgrade -y

Run apt update and apt upgrade to refresh and install package updates. This ensures security and stability, a core task for admins managing Linux servers in production.

9. Why would you use uptime to check Linux server performance?

• Shows system uptime
• Displays load averages
• Indicates performance
  The uptime command reveals system load and runtime. Checking it helps admins assess performance, a critical skill for maintaining stable Linux servers under heavy workloads.

10. When would you use who to monitor user activity on a Linux server?

The who command is used to list logged-in users and their sessions.

• Shows login details
• Monitors with who -a
• Enhances security, a core Linux principle

11. Where would you use a command to check disk I/O performance?

• Use iostat -x
• Monitors disk metrics
• Identifies bottlenecks
  The iostat command tracks disk I/O performance.
  This is vital for optimizing storage in Linux servers.
  Admins rely on it to prevent slowdowns in production systems.

12. Which command restarts a Linux service without downtime?

sudo systemctl reload nginx

Use systemctl reload to refresh a service like Nginx without stopping it. This maintains uptime, a critical task for admins managing Linux servers in high-availability environments.

13. What command would you use to check system boot time?

The systemd-analyze command shows boot time details for performance analysis.

• Use systemd-analyze time
• Check bottlenecks with systemd-analyze blame
• Optimizes startup, a core Linux task
  This ensures efficient server initialization in production.

14. How would you use a command to configure a new user on a Linux server?

sudo adduser newuser
sudo usermod -aG sudo newuser

Run adduser to create a user and usermod to grant sudo privileges. This sets up secure access, a core task for admins managing Linux servers in enterprise environments.

15. Why would you use lscpu to assess Linux server hardware?

• Displays CPU details
• Shows core count
• Identifies architecture
  The lscpu command provides CPU information.
  It aids hardware assessment.
  This ensures optimal resource allocation in Linux systems.

16. When would you use lsblk to manage storage on a Linux server?

The lsblk command lists block devices for storage management.

• Shows disk hierarchy
• Identifies mount points
• Enhances storage planning, a core Linux principle
  This supports efficient disk usage in enterprise environments.

17. Where would you use a command to check filesystem health?

sudo fsck /dev/sda1

Use fsck to scan and repair filesystem errors. This ensures data integrity, a vital task for admins maintaining Linux servers in production environments with critical data.

18. Which command checks kernel version on a Linux server?

• uname -r
• Displays kernel release
• Verifies compatibility
  The uname command shows the kernel version.
  This is critical for ensuring software compatibility.
  Admins use it to maintain stable Linux systems.

Scripting Commands

19. What command would you use to debug a Bash script on a Linux server?

The bash -x command traces script execution for debugging.

• Identifies logic errors
• Logs output with set -x
• Ensures reliable scripts, a core Linux principle
  This prevents automation failures in production environments.

20. How would you use a command to automate log cleanup on a Linux server?

sudo find /var/log -type f -name "*.log" -mtime +7 -delete

Use find to delete logs older than seven days. This prevents disk issues, a core task for admins automating Linux server maintenance in production systems.

21. Why would you use awk to process log files on a Linux server?

• Parses text fields
• Filters log data
• Generates reports
  The awk command processes logs efficiently.
  It extracts specific data.
  This aids admins in analyzing Linux server performance.

22. When would you use sed to modify configuration files?

The sed command edits files non-interactively for automation.

• Replaces text with sed s/old/new/
• Backups with -i.bak
• Streamlines configs, a core Linux principle

23. Where would you use a command to schedule a recurring task?

• Use crontab -e
• Schedules tasks
• Automates jobs
  The crontab command sets up recurring tasks.
  This ensures automated maintenance.
  Admins rely on it for consistent Linux operations.

24. Which command validates a Bash script syntax on a Linux server?

bash -n script.sh

Use bash -n to check script syntax without execution. This prevents errors, a critical task for ensuring reliable automation in Linux production environments.

25. What command would you use to find large files on a Linux server?

The find command with size filters locates large files for cleanup.

• Use find / -size +100M
• Lists large files
• Frees disk space, a core Linux task
  This maintains storage efficiency in production systems.

26. How would you use a command to monitor disk space in a script?

df -h | awk '$5 > 80 {print $6 " is at " $5}'

Use df with awk to alert on high disk usage. This automates monitoring, a core task for admins maintaining Linux servers in enterprise environments.

27. Why would you use grep to analyze logs on a Linux server?

• Filters log entries
• Searches patterns
• Speeds analysis
  The grep command extracts relevant log data.
  It simplifies troubleshooting.
  This is vital for diagnosing Linux server issues.

28. When would you use cut to process text on a Linux server?

The cut command extracts specific columns from files or output.

• Uses cut -d',' -f1 for delimiters
• Processes structured data
• Enhances automation, a core Linux principle

29. Where would you use a command to automate user account cleanup?

• Use userdel
• Removes inactive users
• Frees resources
  The userdel command deletes unused accounts.
  This maintains security.
  Admins use it to streamline Linux system management.

30. Which command checks script execution time on a Linux server?

time ./script.sh

Use time to measure script execution duration. This optimizes performance, a critical task for admins ensuring efficient automation in Linux production environments.

31. What command would you use to parse JSON data in a Linux script?

The jq command processes JSON data for automation scripts.

• Filters with jq '.key'
• Parses complex JSON
• Enhances scripting, a core Linux task
  This supports API integration in Linux systems.

32. How would you use a command to automate backup creation?

tar -czf /backup/data_$(date +%F).tar.gz /data

Use tar to create compressed backups with timestamps. This ensures data safety, a core task for admins managing Linux servers in production environments.

33. Why would you use xargs in a Linux script?

• Processes input streams
• Executes commands
• Handles large datasets
  The xargs command enhances script efficiency.
  It manages bulk operations.
  This is critical for automating Linux tasks.

34. When would you use tee in a Linux script?

The tee command writes output to files and stdout simultaneously.

• Uses tee file.log
• Logs script output
• Ensures auditing, a core Linux principle

35. Where would you use a command to monitor script errors?

• Use tail -f
• Tracks log files
• Identifies errors
  The tail command monitors script logs in real-time.
  This aids debugging.
  Admins rely on it for reliable Linux automation.

36. Which command schedules a one-time task on a Linux server?

echo "backup.sh" | at midnight

Use at to schedule a one-time task. This automates temporary jobs, a critical task for admins managing Linux servers in production environments.

Networking Commands

37. What command would you use to check open ports on a Linux server?

The ss command lists open ports for network services.

• Uses ss -tuln
• Shows listening sockets
• Enhances security, a core Linux task
  This identifies vulnerabilities in Linux networks.

38. How would you use a command to test network connectivity?

ping -c 4 google.com

Use ping to test connectivity to a host. This verifies network reachability, a core task for admins troubleshooting Linux servers in enterprise environments.

39. Why would you use netstat to monitor network connections?

• Shows active connections
• Displays ports
• Tracks traffic
  The netstat command monitors network activity.
  It aids troubleshooting.
  This is vital for maintaining Linux network performance.

40. When would you use traceroute to diagnose network issues?

The traceroute command traces packet paths to identify routing issues.

• Uses traceroute host
• Pinpoints delays
• Enhances diagnostics, a core networking principle

41. Where would you use a command to configure network interfaces?

• Use nmcli
• Manages interfaces
• Applies settings
  The nmcli command configures network interfaces.
  This ensures connectivity.
  Admins rely on it for Linux network management.

42. Which command captures network packets on a Linux server?

sudo tcpdump -i eth0

Use tcpdump to capture network packets. This analyzes traffic, a critical task for admins troubleshooting Linux network issues in production environments.

43. What command would you use to check DNS resolution on a Linux server?

The dig command queries DNS for hostname resolution.

• Uses dig example.com
• Shows response times
• Verifies DNS, a core Linux task
  This ensures reliable network connectivity in Linux systems.

44. How would you use a command to monitor bandwidth usage?

sudo iftop -i eth0

Use iftop to monitor real-time bandwidth usage. This identifies network bottlenecks, a core task for admins managing Linux servers in high-traffic environments.

45. Why would you use ip to manage network settings on a Linux server?

• Configures interfaces
• Manages routes
• Sets addresses
  The ip command replaces older tools like ifconfig.
  It streamlines network management.
  This is critical for Linux network administration.

46. When would you use nslookup for DNS troubleshooting?

The nslookup command queries DNS servers for troubleshooting.

• Uses nslookup host
• Verifies records
• Enhances diagnostics, a core networking principle

47. Where would you use a command to check routing tables?

• Use ip route
• Shows routing info
• Verifies paths
  The ip route command displays routing tables.
  This ensures correct traffic flow.
  Admins use it for Linux network stability.

48. Which command tests network latency on a Linux server?

ping -i 0.1 google.com

Use ping with interval options to measure latency. This assesses network performance, a critical task for admins managing Linux servers in enterprise networks.

49. What command would you use to restart a network service?

The systemctl command restarts network services for connectivity.

• Uses systemctl restart networking
• Applies changes
• Ensures uptime, a core Linux task
  This restores network functionality in Linux systems.

50. How would you use a command to configure a static IP?

sudo nmcli con mod eth0 ipv4.addresses 192.168.1.100/24
sudo nmcli con up eth0

Use nmcli to set a static IP and activate the connection. This ensures stable networking, a core task for admins managing Linux servers.

51. Why would you use iftop to monitor network traffic?

• Shows bandwidth usage
• Tracks connections
• Identifies bottlenecks
  The iftop command monitors real-time traffic.
  It aids network optimization.
  This is vital for Linux server performance.

52. When would you use route to manage routing on a Linux server?

The route command manages routing tables for network traffic.

• Adds routes with route add
• Deletes with route del
• Enhances connectivity, a core networking principle

53. Where would you use a command to check firewall rules?

sudo iptables -L -v

Use iptables -L to list firewall rules. This verifies network security, a critical task for admins managing Linux servers in production environments.

54. Which command monitors SSH connections on a Linux server?

The ss command with filters shows active SSH connections.

• Uses ss -tnp | grep ssh
• Tracks sessions
• Enhances security, a core Linux task
  This monitors remote access in Linux systems.

Security Commands

55. What command would you use to check user login attempts?

• last
• Shows login history
• Detects unauthorized access
  The last command tracks user logins.
  It aids security auditing.
  This is vital for protecting Linux servers.

56. How would you use a command to secure SSH access on a Linux server?

sudo nano /etc/ssh/sshd_config
# Set: PermitRootLogin no
sudo systemctl restart sshd

Edit sshd_config to disable root login and restart SSH. This enhances security, a core task for admins managing Linux servers in enterprise environments.

57. Why would you use auditctl to monitor system events?

• Tracks file access
• Logs system calls
• Ensures compliance
  The auditctl command monitors system activity.
  It supports security audits.
  This is critical for Linux server compliance.

58. When would you use fail2ban to protect a Linux server?

The fail2ban command blocks brute-force attacks on services like SSH.

• Configures jails in /etc/fail2ban
• Monitors logs
• Enhances security, a core Linux principle

59. Where would you use a command to check open ports for vulnerabilities?

• Use nmap localhost
• Scans open ports
• Identifies risks
  The nmap command audits network security.
  This is vital for protecting Linux servers.
  Admins rely on it for vulnerability assessment.

60. Which command checks SELinux status on a Linux server?

getenforce
# or
sestatus

Use getenforce or sestatus to verify SELinux enforcement. This ensures security, a critical task for admins managing Linux servers in high-security environments.

61. What command would you use to scan for malware on a Linux server?

The clamscan command scans for malware to secure systems.

• Uses clamscan -r /
• Logs infections
• Protects data, a core Linux task
  This ensures Linux server integrity in production.

62. How would you use a command to restrict file permissions?

sudo chmod 600 /etc/securefile
sudo chown root:root /etc/securefile

Use chmod and chown to restrict file access. This secures sensitive data, a core task for admins managing Linux servers in enterprise environments.

63. Why would you use chage to manage user passwords?

• Sets password expiry
• Enforces policies
• Enhances security
  The chage command manages password aging.
  It ensures compliance.
  This is vital for Linux server security.

64. When would you use iptables to configure firewall rules?

The iptables command sets firewall rules to secure network traffic.

• Uses iptables -A INPUT
• Saves with iptables-save
• Protects services, a core Linux principle

65. Where would you use a command to monitor security logs?

• Use tail -f /var/log/auth.log
• Tracks login attempts
• Detects breaches
  The tail command monitors security logs.
  This is critical for Linux server protection.
  Admins use it to detect unauthorized access.

66. Which command locks a user account on a Linux server?

sudo passwd -l user

Use passwd -l to lock a user account. This prevents unauthorized access, a critical task for admins securing Linux servers in enterprise environments.

67. What command would you use to check file integrity on a Linux server?

The md5sum command verifies file integrity against checksums.

• Uses md5sum file
• Compares hashes
• Ensures authenticity, a core Linux task
  This detects tampering in Linux systems.

68. How would you use a command to configure AppArmor profiles?

sudo aa-genprof /usr/bin/app
sudo aa-enforce /etc/apparmor.d/*

Use aa-genprof to create and aa-enforce to apply AppArmor profiles. This restricts applications, a core task for admins securing Linux servers.

69. Why would you use pam_tally2 to manage login attempts?

• Tracks login failures
• Locks accounts
• Prevents brute-force
  The pam_tally2 command secures authentication.
  It enforces login policies.
  This is vital for Linux server security.

70. When would you use ufw to manage firewall settings?

The ufw command simplifies firewall configuration for security.

• Enables with ufw enable
• Configures with ufw allow
• Enhances protection, a core Linux principle

71. Where would you use a command to audit user permissions?

• Use getfacl
• Shows file ACLs
• Verifies access
  The getfacl command audits permissions.
  This ensures secure access control.
  Admins rely on it for Linux security.

72. Which command generates SSH keys on a Linux server?

ssh-keygen -t rsa -b 4096

Use ssh-keygen to create secure SSH keys. This enables safe remote access, a critical task for admins managing Linux servers in distributed environments.

Troubleshooting Commands

73. What command would you use to diagnose a Linux server crash?

The dmesg command with error filters identifies crash causes.

• Uses dmesg | grep error
• Analyzes kernel logs
• Restores stability, a core Linux task
  This diagnoses issues in production systems.

74. How would you use a command to troubleshoot network connectivity?

ping -c 4 8.8.8.8
traceroute 8.8.8.8

Use ping and traceroute to test connectivity and trace routes. This identifies network issues, a core task for admins troubleshooting Linux servers.

75. Why would you use strace to debug a Linux application?

• Traces system calls
• Identifies errors
• Logs interactions
  The strace command debugs application issues.
  It pinpoints failures.
  This is vital for Linux troubleshooting.

76. When would you use journalctl to troubleshoot a Linux server?

The journalctl command analyzes systemd logs for system issues.

• Filters with journalctl -u
• Monitors with journalctl -f
• Enhances diagnostics, a core Linux principle

77. Where would you use a command to check disk errors?

• Use smartctl -a /dev/sda
• Shows disk health
• Detects failures
  The smartctl command monitors disk health.
  This prevents data loss.
  Admins use it for Linux reliability.

78. Which command monitors process resource usage on a Linux server?

top -R

Use top -R to monitor process CPU and memory usage. This identifies bottlenecks, a critical task for admins troubleshooting Linux servers in production.

79. What command would you use to find a hung process on a Linux server?

The ps command with state filters finds hung processes.

• Uses ps -aux | grep D
• Identifies blocked tasks
• Restores performance, a core Linux task
  This resolves system slowdowns in production.

80. How would you use a command to check network latency?

ping -i 0.1 -c 10 google.com

Use ping with interval options to measure network latency. This assesses performance, a core task for admins managing Linux servers in enterprise networks.

81. Why would you use lsof to troubleshoot file access issues?

• Lists open files
• Shows process IDs
• Identifies conflicts
  The lsof command tracks file usage.
  It aids troubleshooting.
  This is vital for Linux system stability.

82. When would you use perf to analyze Linux performance?

The perf command profiles CPU and memory for optimization.

• Records with perf record
• Analyzes with perf report
• Enhances diagnostics, a core Linux principle

83. Where would you use a command to check kernel module issues?

• Use lsmod
• Lists loaded modules
• Verifies functionality
  The lsmod command checks kernel modules.
  This ensures system stability.
  Admins rely on it for Linux troubleshooting.

84. Which command restarts a hung service on a Linux server?

sudo systemctl restart nginx

Use systemctl restart to restart a hung service like Nginx. This restores functionality, a critical task for admins managing Linux servers in production.

85. What command would you use to check filesystem corruption?

The fsck command scans and repairs filesystem errors.

• Uses fsck /dev/sda1
• Runs in single-user mode
• Ensures integrity, a core Linux task
  This prevents data loss in Linux systems.

86. How would you use a command to monitor system calls?

sudo strace -p 1234

Use strace to trace system calls for a process. This debugs application issues, a core task for admins troubleshooting Linux servers in production.

87. Why would you use sar to monitor Linux performance?

• Tracks CPU usage
• Monitors disk I/O
• Generates reports
  The sar command collects performance metrics.
  It aids optimization.
  This is vital for Linux server efficiency.

Cloud and Container Commands

88. When would you use docker to manage containers on a Linux server?

The docker command manages containers for application deployment.

• Builds with docker build
• Runs with docker run
• Enhances portability, a core Linux principle

89. Where would you use a command to check container status?

• Use docker ps
• Lists running containers
• Shows status
  The docker ps command monitors containers.
  This ensures application uptime.
  Admins use it for Linux container management.

90. Which command checks Kubernetes pod health on a Linux server?

kubectl get pods

Use kubectl get pods to check pod status. This ensures cluster health, a critical task for admins managing Linux-based Kubernetes deployments.

91. What command would you use to monitor container resource usage?

The docker stats command tracks container CPU and memory usage.

• Uses docker stats --format
• Monitors performance
• Optimizes resources, a core Linux task
  This ensures efficient container operations in Linux systems.

92. How would you use a command to scale a Kubernetes deployment?

kubectl scale deployment myapp --replicas=3

Use kubectl scale to adjust deployment replicas. This ensures scalability, a core task for admins managing Linux-based Kubernetes clusters in production.

93. Why would you use kubectl to troubleshoot Kubernetes issues?

• Inspects pods
• Checks logs
• Diagnoses failures
  The kubectl command debugs Kubernetes clusters.
  It pinpoints issues.
  This is vital for Linux-based cloud deployments.

94. When would you use docker-compose on a Linux server?

The docker-compose command manages multi-container applications.

• Defines services in YAML
• Runs with docker-compose up
• Simplifies deployments, a core Linux principle

95. Where would you use a command to check cloud instance status?

• Use aws ec2 describe-instances
• Shows instance details
• Verifies status
  The AWS CLI command monitors cloud instances.
  This ensures uptime.
  Admins rely on it for Linux cloud management.

96. Which command pulls a Docker image on a Linux server?

docker pull nginx:latest

Use docker pull to download a container image. This prepares deployments, a critical task for admins managing Linux-based containerized applications.

97. What command would you use to monitor AWS EC2 metrics?

The aws cloudwatch command retrieves EC2 performance metrics.

• Uses aws cloudwatch get-metric-statistics
• Tracks CPU usage
• Optimizes performance, a core Linux task
  This ensures efficient cloud operations in Linux systems.

98. How would you use a command to configure a Kubernetes service?

kubectl expose deployment myapp --port=80 --type=LoadBalancer

Use kubectl expose to create a service for a deployment. This enables access, a core task for admins managing Linux-based Kubernetes clusters.

99. Why would you use prometheus to monitor a Linux server?

• Collects metrics
• Generates alerts
• Tracks performance
  The prometheus command monitors system health.
  It aids optimization.
  This is vital for Linux server reliability.

100. When would you use aws CLI to manage Linux instances?

The aws CLI manages EC2 instances for cloud operations.

• Starts with aws ec2 start-instances
• Stops with aws ec2 stop-instances
• Enhances automation, a core Linux principle

101. Where would you use a command to check container logs?

• Use docker logs
• Shows container output
• Aids debugging
  The docker logs command inspects container issues.
  This is critical for troubleshooting.
  Admins use it for Linux container management.

102. Which command restarts a Kubernetes pod on a Linux server?

kubectl delete pod mypod --force

Use kubectl delete to restart a pod by force. This resolves issues, a critical task for admins managing Linux-based Kubernetes clusters.

103. What command would you use to check cloud network configurations?

The aws ec2 describe-security-groups command lists security group rules.

• Verifies inbound rules
• Checks outbound access
• Ensures connectivity, a core Linux task
  This maintains secure cloud networking in Linux systems.

104. How would you use a command to monitor Kubernetes cluster health?

kubectl cluster-info
kubectl get nodes

Use kubectl to check cluster and node status. This ensures reliability, a core task for admins managing Linux-based Kubernetes deployments.

105. Why would you use terraform to manage Linux infrastructure?

• Defines infrastructure as code
• Automates provisioning
• Ensures consistency
  The terraform command streamlines cloud setups.
  It supports scalability.
  This is vital for Linux-based cloud environments.

Tips to Ace Linux Command-Based Interviews

• Practice core Linux commands
• Build scripting and automation labs
• Master systemctl, journalctl, and kubectl
• Study networking and security commands
• Review Linux documentation
• Explain command usage clearly with technical precision