#Linux

Last updated    - V6 (16-Sep-2025)

Key Concepts

Topic	Sub-Topics	Basic	Intermediate	Advanced	Expert
Linux Basics	Linux distributions, File system structure, Kernel vs User space, Commands overview	✅	✅
File Management	File types, Permissions, Ownership, Links, File operations	✅	✅	✅
Process Management	ps, top, htop, jobs, kill, nice, renice, signals	✅	✅	✅	✅
Users & Groups	Adding/removing users, Groups, sudo, permissions, /etc/passwd, /etc/group	✅	✅	✅	✅
Package Management	apt, yum, rpm, dpkg, snap, package updates	✅	✅	✅	✅
Shell Scripting	Variables, Loops, Conditionals, Functions, Cron jobs	✅	✅	✅	✅
Networking	ifconfig/ip, netstat, ss, ping, traceroute, firewall, ports	✅	✅	✅	✅
Disk & Storage	df, du, mount/umount, LVM, RAID, quotas	✅	✅	✅	✅
System Monitoring	top, vmstat, iostat, sar, free, uptime, logs	✅	✅	✅	✅
Logging & Troubleshooting	syslog, journalctl, dmesg, logrotate, error analysis	✅	✅	✅	✅
Security & Permissions	SELinux, AppArmor, chmod, chown, sudoers, firewalld	✅	✅	✅	✅
Networking Services	SSH, FTP, HTTP, DNS, DHCP, NFS, Samba	✅	✅	✅	✅
Kernel & Modules	Kernel parameters, sysctl, modules, modprobe, kernel tuning		✅	✅	✅
Performance Tuning	CPU, Memory, I/O tuning, ulimit, caching, tuning tools		✅	✅	✅
Advanced Topics	Containers (Docker), Virtualization, Systemd, automation, DevOps integration		✅	✅	✅

Interview question

1. Linux Basics

1. What is Linux and how is it different from Unix?
2. What are the main Linux distributions?
3. Explain the difference between Kernel and User Space.
4. What is the Linux file system hierarchy?
5. What are inodes in Linux?
6. What are symbolic and hard links?
7. What is a shell in Linux?
8. What are the common Linux shells?
9. What is the difference between GUI and CLI in Linux?
10. How to check the current Linux version?
11. What is the purpose of /etc directory?
12. What are runlevels in Linux?
13. How to switch between runlevels?
14. What are init and systemd?
15. What is the purpose of /proc directory?
16. How to check uptime and load average?
17. How to find the Linux kernel version?
18. What is a daemon in Linux?
19. How to check system architecture?
20. How to use man pages effectively?

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2. File Management

1. What are different file types in Linux?
2. How to change file permissions using chmod?
3. How to change ownership using chown?
4. How to create symbolic and hard links?
5. How to list files with detailed information?
6. What is the difference between relative and absolute paths?
7. How to search for files using find and locate?
8. How to check disk usage with du and df?
9. How to monitor file system usage?
10. How to compress and decompress files using tar, gzip, bzip2?
11. How to check file content using cat, less, more?
12. How to edit files using vi or nano?
13. How to monitor changes in files using tail -f?
14. How to compare files using diff and cmp?
15. How to backup files using rsync?
16. How to find large files on the system?
17. How to change timestamps using touch?
18. How to manage hidden files?
19. How to set default permissions using umask?
20. How to mount and unmount file systems?

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3. Process Management

1. How to list running processes using ps and top?
2. How to kill a process using kill and killall?
3. How to change process priority using nice and renice?
4. What are foreground and background processes?
5. How to manage jobs using jobs, fg, bg commands?
6. How to monitor CPU and memory usage per process?
7. How to handle zombie processes?
8. How to handle orphan processes?
9. How to use systemctl to manage services?
10. How to automate process monitoring using scripts?
11. What is a PID and how to find it?
12. How to track process resource usage using pidstat?
13. How to manage threads in Linux processes?
14. How to use pgrep to find processes?
15. How to use top and htop effectively?
16. How to monitor real-time processes with watch command?
17. How to manage system services with service command?
18. How to limit process resources using ulimit?
19. How to analyze CPU-bound processes?
20. How to analyze memory-bound processes?

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4. Users & Groups

1. How to add and remove users?
2. How to add and remove groups?
3. How to modify user properties?
4. How to assign users to groups?
5. How to switch users using su and sudo?
6. What is the difference between su and sudo?
7. How to configure password policies?
8. How to check user login history using last command?
9. How to restrict user access?
10. How to implement sudoers configuration?
11. How to lock and unlock user accounts?
12. How to delete users and remove home directories?
13. How to check current logged-in users?
14. How to list all users and groups?
15. How to manage SSH access for users?
16. How to configure user quotas?
17. How to monitor user activity?
18. How to set default shell for a user?
19. How to create system users?
20. How to manage user environment variables?

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5. Package Management

1. What are different package managers in Linux?
2. How to install packages using apt?
3. How to install packages using yum?
4. How to remove packages using rpm?
5. How to update all packages in a system?
6. How to check installed packages?
7. How to search for packages?
8. How to manage repositories?
9. How to resolve package dependencies?
10. How to clean package cache?
11. How to verify installed packages?
12. How to downgrade a package?
13. How to install packages from source?
14. How to use dpkg to manage packages?
15. How to use snap packages?
16. How to check package versions?
17. How to configure third-party repositories?
18. How to manage kernel updates?
19. How to handle broken packages?
20. How to automate package updates?

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6. Shell Scripting

1. What are shell scripts?
2. How to create and execute a shell script?
3. How to define variables in shell scripts?
4. How to use command-line arguments in scripts?
5. How to use loops in shell scripting?
6. How to use conditional statements?
7. How to define functions in shell scripts?
8. How to debug shell scripts?
9. How to use exit codes?
10. How to read user input in shell scripts?
11. How to schedule scripts using cron jobs?
12. How to redirect input and output?
13. How to use pipes in shell scripting?
14. How to handle errors in scripts?
15. How to implement logging in scripts?
16. How to use arrays in shell scripts?
17. How to use case statements?
18. How to use traps for signals?
19. How to pass environment variables to scripts?
20. How to implement reusable scripts?

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7. Networking

1. How to check network interfaces?
2. How to check IP address using ifconfig/ip?
3. How to check open ports using netstat/ss?
4. How to test connectivity using ping?
5. How to trace route using traceroute?
6. How to monitor network traffic using tcpdump?
7. How to configure firewall using iptables/firewalld?
8. How to configure routing tables?
9. How to check DNS resolution?
10. How to troubleshoot network issues?
11. How to use curl and wget for testing connections?
12. How to check MAC address of network interface?
13. How to configure static IP address?
14. How to configure DHCP client?
15. How to manage network services?
16. How to monitor bandwidth usage?
17. How to test port connectivity using telnet?
18. How to analyze packet loss?
19. How to implement NAT and port forwarding?
20. How to configure VPN connections?

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8. Disk & Storage

1. How to check disk usage using df and du?
2. How to mount and unmount file systems?
3. How to create partitions using fdisk or parted?
4. How to format partitions?
5. How to create and manage LVM?
6. How to extend or shrink logical volumes?
7. How to configure RAID levels?
8. How to check disk health using smartctl?
9. How to monitor I/O performance using iostat?
10. How to implement disk quotas?
11. How to create swap space?
12. How to enable or disable swap?
13. How to configure automatic mounting?
14. How to handle disk failures?
15. How to backup and restore data?
16. How to use rsync for file transfer?
17. How to encrypt disk partitions?
18. How to monitor disk latency?
19. How to check inode usage?
20. How to use tmpfs for temporary storage?

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9. System Monitoring

1. How to monitor CPU usage using top or htop?
2. How to monitor memory usage using free and vmstat?
3. How to monitor I/O using iostat and sar?
4. How to check uptime and load average?
5. How to monitor running processes?
6. How to check swap usage?
7. How to monitor logs for system issues?
8. How to use dstat for real-time monitoring?
9. How to monitor network traffic?
10. How to use glances for system overview?
11. How to monitor disk usage and inode usage?
12. How to track process resource usage?
13. How to monitor system boot time?
14. How to monitor cron job execution?
15. How to monitor system performance over time?
16. How to use atop for performance analysis?
17. How to monitor system limits using ulimit?
18. How to monitor hardware temperature?
19. How to monitor CPU frequency and scaling?
20. How to monitor kernel logs?

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10. Logging & Troubleshooting

1. How to check system logs using /var/log?
2. How to use journalctl for systemd logs?
3. How to monitor real-time logs using tail -f?
4. How to analyze dmesg output?
5. How to rotate logs using logrotate?
6. How to debug boot issues?
7. How to troubleshoot service failures?
8. How to find failed login attempts?
9. How to analyze application logs?
10. How to configure logging for custom applications?
11. How to debug network issues?
12. How to check file system errors?
13. How to handle kernel panics?
14. How to recover from crashed services?
15. How to monitor disk space warnings?
16. How to check SELinux audit logs?
17. How to check firewall logs?
18. How to debug package installation issues?
19. How to monitor cron job errors?
20. How to configure centralized logging?

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11. Security & Permissions

1. How to use chmod to change file permissions?
2. How to use chown and chgrp for ownership?
3. What is the difference between su and sudo?
4. How to configure sudoers file?
5. How to enable and configure SELinux?
6. How to use AppArmor for security?
7. How to configure firewall rules?
8. How to implement file access control lists (ACLs)?
9. How to monitor failed login attempts?
10. How to secure SSH access?
11. How to configure key-based authentication for SSH?
12. How to disable root login over SSH?
13. How to implement password policies?
14. How to encrypt files and directories?
15. How to monitor system for security breaches?
16. How to manage user permissions and roles?
17. How to apply security patches?
18. How to configure auditd for auditing?
19. How to implement network security monitoring?
20. How to secure cron jobs and scheduled tasks?

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12. Advanced Topics

1. How to use containers (Docker) in Linux?
2. How to use virtualization with KVM or VirtualBox?
3. How to manage services using systemd?
4. How to automate tasks using Ansible?
5. How to configure kernel parameters with sysctl?
6. How to tune CPU and memory for performance?
7. How to implement monitoring with Prometheus and Grafana?
8. How to configure advanced networking (VLANs, bridges)?
9. How to use cgroups for resource control?
10. How to debug performance issues using strace?
11. How to use lsof to list open files?
12. How to handle large log files efficiently?
13. How to implement software RAID?
14. How to set up NFS and Samba file sharing?
15. How to use iptables and nftables for advanced firewalling?
16. How to analyze kernel performance using perf?
17. How to configure system for high availability?
18. How to implement load balancing?
19. How to use cron and at for scheduling?
20. How to integrate Linux with cloud platforms (AWS, Azure, GCP)?

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13. Troubleshooting & Best Practices

1. How to troubleshoot boot issues?
2. How to recover from a crashed service?
3. How to debug memory leaks?
4. How to identify CPU bottlenecks?
5. How to handle disk full issues?
6. How to analyze slow network performance?
7. How to recover deleted files?
8. How to implement system backup strategies?
9. How to apply patch management effectively?
10. What are the best practices for Linux system administration?

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