What is a process in Linux and how do you list running processes?

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Linux Interview Questions

  1. [JUNIOR] What is Linux and how does it differ from Unix?
  2. [JUNIOR] What is the Linux kernel and what are its main functions?
  3. [JUNIOR] What is the difference between a root user and a regular user in Linux?
  4. [JUNIOR] What is the difference between symbolic links and hard links in Linux?
  5. [JUNIOR] What are the basic file permission types in Linux and how do you read them?
  6. [JUNIOR] How do you check disk usage and free space on a Linux system?
  7. [JUNIOR] What is the sudo command and why is it preferred over logging in as root?
  8. [MID] How do Linux file permissions work, including the numeric (octal) notation, and how do you modify them with chmod?
  9. [MID] How do cron jobs work and how do you schedule recurring tasks using crontab?
  10. [MID] How do you monitor system resources using commands like top, htop, vmstat, and iostat?
  11. [MID] What is load average in Linux and how do you interpret the three numbers it shows?
  12. [MID] How does the systemd init system work and how does it differ from the traditional SysVinit?
  13. [SENIOR] How do you troubleshoot a Linux server experiencing high load average but low CPU utilization?
  14. [SENIOR] How do you harden and secure SSH access on a production Linux server?
  15. [JUNIOR] What are the basic components of the Linux operating system?
  16. [JUNIOR] What is a Linux distribution and how do common distributions differ?
  17. [JUNIOR] What is BASH and how does it differ from other Linux shells?
  18. [JUNIOR] What is swap space in Linux and why is it needed?
  19. [JUNIOR] What is an inode in Linux?
  20. [JUNIOR] What is the grep command and how is it used for text searching?
  21. [JUNIOR] What is a pipe in Linux and how does it enable command chaining?
  22. [JUNIOR] What is a process in Linux and how do you list running processes?
  23. [JUNIOR] How do you find a file by name in Linux?
  24. [MID] How do soft links and hard links differ at the filesystem level in terms of inodes and data blocks?
  25. [MID] What are the different process states in Linux and how does the kernel manage process transitions?
  26. [MID] What is a zombie process, how is it created, and how do you identify and clean up zombie processes?
  27. [MID] How do you configure passwordless SSH authentication between two Linux servers?
  28. [MID] How do you permanently mount filesystems using /etc/fstab?
  29. [MID] What is LVM and how does it simplify disk management in production environments?
  30. [MID] How do you manage services using systemctl commands?
  31. [MID] How do you find which process is listening on a specific port?
  32. [SENIOR] How do you tune Linux kernel parameters using sysctl for performance optimization?
  33. [SENIOR] What is SELinux, how does it differ from traditional DAC permissions, and how do you configure its policies and modes?
  34. [SENIOR] How do you troubleshoot a Linux system that fails to boot?
  35. [SENIOR] How do you use strace to debug application-level issues and trace system calls?
  36. [SENIOR] How do you investigate a suspected security breach on a Linux server?
  37. [JUNIOR] What are the different types of shells available in Linux?
  38. [JUNIOR] What are daemons in Linux and how do they work?
  39. [JUNIOR] What are environment variables in Linux and how do you display them?
  40. [JUNIOR] What are the three standard streams (stdin, stdout, stderr) in Linux?
  41. [JUNIOR] What is the difference between absolute and relative file paths in Linux?
  42. [JUNIOR] What is I/O redirection in Linux and what operators are used for it?
  43. [JUNIOR] What is a package manager and how do RPM-based and Debian-based package managers differ?
  44. [JUNIOR] How do you terminate a process in Linux?
  45. [MID] What is umask and how does it affect default file permissions?
  46. [MID] What are foreground and background processes and how do you manage them using job control?
  47. [MID] How do you create and manage user accounts and groups in Linux?
  48. [MID] What is rsync and how does it differ from scp for file synchronization?
  49. [MID] How do you check and configure network interfaces and IP addresses on a Linux system?
  50. [MID] What is the /proc filesystem and what kind of runtime information does it expose?
  51. [MID] How does log rotation work in Linux and how do you configure logrotate?
  52. [MID] How do you redirect both stdout and stderr to a file or to different destinations?
  53. [MID] What is the /etc/hosts file used for and how does it interact with DNS resolution?
  54. [MID] How do you use the find command with exec to perform bulk operations on matching files?
  55. [SENIOR] How do you extend a logical volume and resize a filesystem without downtime?
  56. [SENIOR] How do you investigate and recover from a kernel panic?
  57. [SENIOR] How do you use tcpdump for network traffic capture and analysis?
  58. [SENIOR] How do you handle centralized log management at scale using syslog and log aggregation tools?
  59. [SENIOR] How do you tune Linux networking stack parameters for high-throughput applications?
  60. [SENIOR] How do you identify and limit resource usage for processes using ulimit and cgroups?
  61. [SENIOR] A production server's disk usage on /var suddenly hits 100%. What steps do you take to diagnose and resolve the issue?
  62. [EXPERT] How do cgroups v1 and v2 work in Linux and how are they used for resource isolation in container runtimes?
  63. [EXPERT] How do Linux namespaces (PID, network, mount, user, UTS, IPC) provide process isolation and what role do they play in container technologies?
  64. [JUNIOR] What is CLI and GUI in the context of Linux?
  65. [JUNIOR] What are hidden files in Linux and how do you view them?
  66. [MID] What is the difference between iptables and nftables?
  67. [MID] How do you troubleshoot DNS resolution issues on a Linux system?
  68. [MID] How do you compress and decompress files and archives using tar, gzip, and bzip2?
  69. [MID] What are sticky bits, setuid, and setgid permissions and when are they used?
  70. [MID] What are runlevels and systemd targets and how do they control the system state?
  71. [MID] How do you add swap space to a running Linux system?
  72. [SENIOR] How do you configure and manage software RAID arrays in Linux?
  73. [SENIOR] How do you perform zero-downtime deployments on Linux servers?
  74. [SENIOR] How would you troubleshoot a service that starts successfully but crashes after running for several hours?
  75. [SENIOR] How do you manage and troubleshoot kernel modules in Linux?
  76. [SENIOR] How do you configure a Linux firewall for a multi-tier application architecture?
  77. [SENIOR] How do you investigate why a server rebooted unexpectedly?
  78. [EXPERT] How do you design a highly available Linux-based infrastructure with automated failover?
  79. [MID] What is the difference between cron and anacron?
  80. [MID] What is NFS and how do you mount a remote NFS share?
  81. [MID] What is the difference between NFS and Samba for network file sharing?
  82. [SENIOR] What is the chroot command and how is it used for process isolation?
  83. [SENIOR] How do you configure NIC bonding or teaming for redundancy and increased throughput?
  84. [SENIOR] How do you perform a kernel upgrade on a production system with minimal risk?
  85. [EXPERT] How does the Linux virtual memory subsystem work, including page tables, TLB, and the OOM killer?
  86. [EXPERT] How do you manage and enforce consistent configuration across a large fleet of Linux servers?
  87. [EXPERT] How do you design Linux systems for horizontal scalability and what kernel tuning is required for high-concurrency workloads?
  88. [SENIOR] What is RAID and how do the different RAID levels (0, 1, 5, 6, 10) compare in terms of performance and redundancy?
  89. [EXPERT] How does the Linux I/O scheduler work and how do you choose between different schedulers for various workloads?
  90. [EXPERT] What is eBPF and how can it be used for observability, networking, and security in Linux?
  91. [EXPERT] How does the Linux boot process work from BIOS/UEFI through bootloader, kernel initialization, to user space?
  92. [EXPERT] How do you troubleshoot performance issues related to NUMA topology on multi-socket Linux systems?