120 RHCSA Interview Questions and Answers [Red Hat Certified SysAdmin – 2025]

System Configuration and Management

1. What is the purpose of the /etc/fstab file in RHEL?

The /etc/fstab file defines how disk partitions and filesystems are mounted at boot. It lists mount points, filesystem types, and options like read-only. This ensures consistent storage configuration, enabling automatic mounting of the root filesystem or external drives for seamless system operation.

2. Why is the useradd command essential for system administration?

• Creates new user accounts with unique identifiers.
• Configures home directories and default shells.
• Ensures secure access for users.
  The useradd command streamlines user management by setting up accounts with tailored environments, vital for multi-user systems where access control and security are priorities.

3. When should you use the systemctl command to manage services?

Use systemctl during maintenance or configuration to control services. It starts, stops, or enables services at boot, ensuring availability. For instance, enabling the Apache service ensures it runs automatically, supporting consistent web server functionality across system restarts.

4. Where are system logs typically stored in RHEL?

• Found in the /var/log directory.
• Includes /var/log/messages for system events.
• Contains /var/log/secure for authentication logs.
  System logs are critical for diagnosing issues and monitoring security, allowing administrators to track errors or unauthorized access attempts efficiently.

5. Who can modify the /etc/sudoers file, and what precautions are needed?

Only root or sudo-privileged users can edit /etc/sudoers. Using visudo ensures syntax validation to avoid errors that could lock out administrative access. Backing up the file and testing changes, like granting specific privileges, prevents disruptions in system management.

6. Which command displays detailed file permissions in a directory?

The ls -l command lists permissions, ownership, and metadata. It shows read, write, and execute rights for owner, group, and others. This helps administrators verify access controls, ensuring files like configuration scripts are restricted appropriately.

7. How do you configure a static IP address on an RHEL system?

Edit the network configuration file in /etc/sysconfig/network-scripts, setting BOOTPROTO to none, and specifying IPADDR, NETMASK, and GATEWAY. Restart networking with nmcli con reload. This ensures reliable connectivity for servers, maintaining consistent network access for critical applications.

8. What does the yum command do in RHEL package management?

The yum command, often replaced by dnf, manages software packages. It installs, updates, or removes packages while resolving dependencies. This simplifies software maintenance, ensuring systems have the latest tools and security patches for optimal performance.

9. Why is SELinux important for system security?

• Enforces mandatory access controls.
• Restricts processes to predefined policies.
• Protects against unauthorized access.
  SELinux enhances RHEL security by limiting process privileges, even for root users, reducing risks from exploits and ensuring system integrity in enterprise environments.

10. When do you use the chown command in RHEL?

Use chown to change file or directory ownership during access control management. It assigns users or groups to resources, ensuring secure file sharing. This is critical for collaborative projects where specific users need access to shared directories or files.

11. Where is the default location for user home directories?

User home directories are in /home, like /home/jdoe for user jdoe. Created during account setup, these directories store user-specific configurations and data, organizing personal files and ensuring data isolation for efficient multi-user system management.

12. Who is responsible for managing the /etc/hosts file?

• System administrators manage /etc/hosts.
• Maps IP addresses to hostnames.
• Supports local name resolution.
  The /etc/hosts file enables hostname-to-IP mappings without DNS, critical for small networks or systems needing fast, reliable network communication.

13. Which command manages disk partitions in RHEL?

The fdisk utility creates, deletes, or modifies partitions. It supports setting partition types and sizes, preparing disks for filesystems or swap space. This enables efficient storage allocation, ensuring optimal resource use for RHEL systems.

14. How do you check the current runlevel in RHEL?

• Use systemctl get-default for default target.
• Run who -r for current runlevel.
• Displays system state details.
  These commands verify the system’s operational mode, like graphical or multi-user, ensuring alignment with intended functionality.

15. What is the role of the crontab command?

The crontab command schedules automated tasks. Users edit crontab to run scripts at specific times, like daily backups. This reduces manual effort, ensuring consistent execution of repetitive tasks, such as system maintenance or log rotation, in RHEL environments.

16. Why do administrators use the grep command?

Administrators use grep to search text patterns in files or command outputs. It filters data, like error messages in logs, for quick analysis. This streamlines troubleshooting, helping identify issues or security events efficiently in large datasets.

17. When should you reboot an RHEL system?

• Reboot after kernel updates.
• Apply major configuration changes.
• Resolve system hangs or crashes.
  Rebooting ensures new kernels or patches take effect, maintaining system stability and security without disrupting ongoing services unnecessarily.

18. Where are kernel modules stored in RHEL?

Kernel modules are in /lib/modules/. These loadable components extend kernel functionality, supporting new hardware or filesystems. Administrators access this directory to manage modules, ensuring compatibility with system requirements and hardware configurations.

19. Who can access the root user’s environment directly?

Only root or sudo-privileged users can access the root environment using su - or sudo -i. This restricted access ensures security, as root privileges grant full system control, requiring careful management to prevent unauthorized actions or misconfigurations.

20. Which command monitors real-time system resource usage?

• The top command shows CPU usage.
• Displays memory and process details.
• Identifies resource-intensive tasks.
  The top command helps administrators optimize performance by pinpointing processes consuming excessive resources, ensuring efficient system operation.

21. How do you create a new filesystem on a partition?

Identify the partition, format it with mkfs.ext4, and mount it to a directory like /mnt. This prepares the partition for data storage, ensuring compatibility with RHEL. Proper formatting and mounting enable reliable access for applications or users.

22. What does the passwd command accomplish?

• Updates user passwords.
• Enforces strong password policies.
• Enhances account security.
  The passwd command ensures accounts remain secure by allowing password updates, reducing risks of unauthorized access and maintaining system integrity.

23. Why is the iptables command used in older RHEL versions?

In older RHEL versions, iptables configures firewall rules to secure network traffic. It filters packets, allowing specific connections like SSH while blocking unauthorized access. This protects systems from external threats, ensuring secure communication for critical services.

24. When is the nmcli command preferred for network configuration?

Use nmcli for automating or managing complex network settings. It integrates with NetworkManager, simplifying tasks like setting static IPs. This ensures consistent connectivity for servers, making it ideal for scripting or dynamic network configurations in RHEL.

25. Where do you configure DNS settings in RHEL?

• Configure in /etc/resolv.conf.
• Use NetworkManager tools like nmcli.
• Ensures reliable name resolution.
  DNS settings in /etc/resolv.conf or via nmcli specify servers like 8.8.8.8, supporting network-dependent services and applications.

26. Who benefits from using the visudo command?

System administrators benefit from visudo when editing /etc/sudoers. It validates syntax, preventing errors that could disable sudo access. This ensures safe privilege management, allowing secure configuration of administrative permissions without risking system lockouts.

27. Which utility checks disk usage in RHEL?

• The df command monitors disk usage.
• Shows human-readable sizes with df -h.
• Tracks storage capacity.
  The df command helps administrators identify full disks, plan capacity upgrades, and maintain system performance by monitoring storage.

28. How do you set up a cron job for a specific user?

• Edit with crontab -e -u username.
• Schedule tasks like daily scripts.
• Save to activate the job.
  This automates user-specific tasks, reducing manual effort and ensuring consistent execution of repetitive operations.

29. What is the function of the groupadd command?

The groupadd command creates new groups, simplifying permission management. It assigns shared access to files or resources, enabling collaboration. For example, adding a developers group allows multiple users to access project directories efficiently, streamlining access control.

30. Why do you use the chmod command?

The chmod command modifies file permissions to control access. It ensures only authorized users can read, write, or execute files. This secures sensitive data, like configuration files, by defining precise access levels for owners, groups, and others.

Security and Access Control

31. What is the significance of the /etc/shadow file?

• Stores encrypted user passwords.
• Includes account details like expiration.
• Accessible only to root.
  The /etc/shadow file secures authentication data, preventing unauthorized access and ensuring user account protection in RHEL systems.

32. Why is the firewalld service critical in RHEL?

The firewalld service dynamically manages firewall rules, using zones to control traffic. It ensures network security by allowing essential services while blocking unauthorized access, protecting systems from external threats and maintaining reliable service availability.

33. When should you use the setfacl command?

• Use for fine-grained access control.
• Grants specific user permissions.
• Ideal for complex projects.
  The setfacl command sets Access Control Lists when standard permissions are insufficient, enabling precise access management for collaborative environments.

34. Where are SELinux policies typically stored?

SELinux policies are stored in /etc/selinux for configuration and /var/lib/selinux for policy files. These define process restrictions, ensuring security by preventing unauthorized actions and maintaining compliance across RHEL systems in enterprise settings.

35. Who can execute commands with sudo privileges?

• Users listed in /etc/sudoers.
• Groups with defined sudo access.
• Requires careful configuration.
  Sudo privileges allow controlled administrative actions, ensuring only authorized users perform privileged operations securely.

36. Which command audits user login activity?

The last command displays login history, showing users, timestamps, and hosts. It helps track access, detect unauthorized logins, and maintain security by providing detailed audit trails for monitoring user activity on RHEL systems.

37. How do you lock a user account in RHEL?

Use usermod -L to lock an account, disabling login by modifying /etc/shadow. Unlock with usermod -U. This prevents access while preserving data, useful for temporary restrictions or addressing security concerns without deleting accounts.

38. What does the sshd_config file control?

• Configures SSH daemon settings.
• Sets ports and authentication methods.
• Defines allowed users.
  The /etc/ssh/sshd_config file manages remote access, ensuring secure and customized SSH connections for RHEL systems.

39. Why should you disable root login via SSH?

Disabling root SSH login reduces attack risks, as root is a common target. Setting PermitRootLogin to no in /etc/ssh/sshd_config forces logins via standard users, minimizing damage from compromised credentials and enhancing system security.

40. When is the semanage command used?

Use semanage to manage SELinux policies, like file contexts or port mappings. It ensures services comply with security constraints, allowing applications to function while maintaining strict access controls in RHEL environments.

41. Where are failed login attempts logged?

• Logged in /var/log/secure or /var/log/auth.log.
• Shows user and failure details.
• Helps detect brute-force attacks.
  Monitoring these logs ensures timely security responses, protecting systems from unauthorized access attempts.

42. Who should manage SSH keys for secure access?

System administrators manage SSH keys, generating pairs and configuring authorized_keys files. This enables passwordless, secure remote access, ensuring only authorized users connect to RHEL systems, maintaining security and operational efficiency.

43. Which command displays open ports on a system?

• The ss command lists open ports.
• Shows listening TCP/UDP connections.
• Verifies service accessibility.
  The ss command ensures only necessary ports are open, minimizing security risks and optimizing network performance.

44. How do you configure a user’s password expiration policy?

Use chage to set password aging, like 90-day validity or warning periods. This enforces regular updates, reducing the risk of compromised credentials and ensuring account security across RHEL systems in compliance with organizational policies.

45. What is the purpose of the pam.d directory?

The /etc/pam.d directory holds PAM configuration files, defining authentication rules for services like SSH. It ensures consistent, secure authentication, allowing administrators to enforce password policies or integrate with external authentication systems effectively.

46. Why is the restorecon command used?

• Resets SELinux file contexts.
• Ensures compliance with policies.
• Prevents service violations.
  The restorecon command corrects file contexts after modifications, ensuring services operate within SELinux security boundaries, maintaining system integrity.

47. When should you use the authconfig command?

In older RHEL versions, authconfig configures authentication mechanisms like LDAP. It simplifies integration with enterprise systems, ensuring centralized user management and secure authentication for users accessing RHEL systems in large environments.

48. Where are user group definitions stored?

• Stored in /etc/group.
• Lists groups, GIDs, and members.
• Manages access control.
  The /etc/group file organizes group memberships, ensuring proper access to shared resources in collaborative or restricted environments.

49. Who can view the contents of /var/log/audit/audit.log?

Only root or specifically permitted users can view /var/log/audit/audit.log. This log records SELinux and system audit events, helping administrators analyze security incidents and ensure compliance with organizational security policies.

50. Which command restricts file access to specific users?

The chmod command, paired with chown, restricts file access. It sets permissions to limit read, write, or execute rights, ensuring only authorized users access sensitive data, like configuration files, in RHEL systems.

51. How do you enable SELinux enforcing mode?

• Edit /etc/selinux/config, set SELINUX=enforcing.
• Run setenforce 1 for immediate effect.
• Reboot if needed.
  This activates strict policy enforcement, enhancing security by preventing unauthorized actions in RHEL environments.

52. What does the getfacl command reveal?

The getfacl command displays Access Control Lists, showing granular permissions beyond standard settings. It helps verify complex access configurations, ensuring files or directories have precise access controls for users or groups in collaborative setups.

53. Why is the sshd service restarted after configuration changes?

Restarting sshd applies changes to /etc/ssh/sshd_config, like updated ports or authentication settings. This ensures the SSH daemon reflects new configurations, maintaining secure remote access without requiring a full system reboot, critical for continuous operations.

54. When do you use the auditctl command?

• Configures real-time auditing.
• Monitors critical file changes.
• Aids security compliance.
  The auditctl command tracks modifications to sensitive files, ensuring audit trails for security and compliance in RHEL systems.

55. Where are SSH configuration files stored in RHEL?

SSH configuration files are in /etc/ssh, with sshd_config for server settings and ssh_config for clients. These manage remote access, like port settings or authentication methods, ensuring secure and customized SSH connections for system access.

56. Who can generate a new SSH key pair?

• Any user can generate keys.
• Administrators manage key distribution.
• Ensures secure remote access.
  Users generate SSH keys with ssh-keygen, but administrators configure them for secure, passwordless access to RHEL systems.

57. Which command checks SELinux status?

The getenforce command shows SELinux mode (Enforcing, Permissive, or Disabled). The sestatus command provides detailed policy information. These verify SELinux configuration, ensuring the system operates within defined security parameters for compliance and protection.

58. How do you limit SSH access to specific users?

Edit /etc/ssh/sshd_config, add AllowUsers with specific usernames, and restart sshd. This restricts SSH access to listed users, enhancing security by preventing unauthorized remote logins while allowing access for designated accounts.

59. What is the role of the /etc/passwd file?

• Stores user account details.
• Includes username, UID, and shell.
• Readable by all users.
  The /etc/passwd file defines user information, like home directories, but relies on /etc/shadow for secure password storage.

60. Why is the chage command useful for security?

The chage command manages password aging, enforcing regular updates. It sets validity periods or warnings, reducing risks of compromised credentials. This ensures accounts remain secure, aligning with organizational security policies for RHEL systems.

Storage and Filesystem Management

61. What is the purpose of the mkfs command?

The mkfs command formats partitions to create filesystems, like ext4 or XFS. It prepares storage for data, enabling administrators to configure disks for specific use cases, such as system partitions or data storage, in RHEL environments.

62. Why is LVM (Logical Volume Manager) used in RHEL?

• Enables flexible storage management.
• Supports dynamic volume resizing.
• Simplifies storage allocation.
  LVM allows administrators to extend or shrink volumes without downtime, optimizing storage for changing system needs in enterprise settings.

63. When should you use the fsck command?

Use fsck to check and repair filesystems after crashes or during maintenance. It scans for errors on unmounted filesystems, ensuring integrity and preventing data corruption, which is critical for reliable storage performance in RHEL.

64. Where are swap spaces defined in RHEL?

Swap spaces are defined in /etc/fstab, listing devices or files used for virtual memory. They provide additional memory during high usage, ensuring system stability and preventing crashes for memory-intensive applications or processes.

65. Who can create a new logical volume?

• Root or sudo-privileged users.
• Requires LVM command access.
• Manages volume group resources.
  Creating logical volumes with LVM ensures controlled storage management, preventing unauthorized changes and optimizing disk usage.

66. Which command displays disk usage by directory?

The du command shows directory disk usage. It lists sizes in human-readable format, helping administrators identify space-consuming directories, optimize storage, and plan cleanup tasks to maintain system performance and capacity.

67. How do you extend a logical volume in LVM?

Extend a logical volume by increasing its size with lvextend, then resize the filesystem with resize2fs. Verify with lvs. This dynamically increases storage capacity, ensuring flexibility for growing data needs without disrupting operations.

68. What does the parted command do?

• Manages disk partitions.
• Supports large disk sizes.
• Configures partition tables.
  The parted command enables advanced partitioning, offering flexibility for complex storage setups in RHEL systems.

69. Why is the mount command important?

The mount command integrates filesystems into the directory tree, enabling data access. It connects devices to mount points, allowing administrators to manage storage and ensure applications or users can access required data efficiently.

70. When do you use the blkid command?

• Displays block device attributes.
• Shows UUIDs and filesystem types.
• Aids /etc/fstab configuration.
  The blkid command identifies devices for mounting, ensuring accurate filesystem setup during system boot or maintenance.

71. Where are LVM volume group details stored?

LVM volume group details are in /etc/lvm, with lvm.conf for settings and /etc/lvm/backup for metadata. These store configuration data, enabling administrators to manage storage resources and verify volume group properties effectively.

72. Who can format a new disk partition?

• Root or sudo-privileged users.
• Requires mkfs command access.
• Ensures secure disk preparation.
  Formatting partitions is restricted to administrators to prevent unauthorized changes, ensuring secure storage setup.

73. Which command checks filesystem integrity?

The fsck command scans and repairs filesystems, ensuring reliability. It corrects errors that could cause data loss, maintaining filesystem integrity for stable storage operations in RHEL environments, especially after system crashes.

74. How do you create a swap partition?

Create a partition with fdisk, set type to 82, format with mkswap, and enable with swapon. Add to /etc/fstab for persistence. This provides virtual memory, ensuring system stability during high memory usage.

75. What is the role of the /etc/mtab file?

• Lists currently mounted filesystems.
• Shows devices and mount options.
• Dynamically updated.
  The /etc/mtab file helps administrators verify active mounts and troubleshoot mounting issues in RHEL systems.

76. Why is the xfs_admin command used?

The xfs_admin command manages XFS filesystem attributes, like UUIDs or labels. It ensures proper identification and compatibility, allowing administrators to configure storage for specific use cases, maintaining efficient filesystem operations in RHEL.

77. When should you resize a filesystem?

• Resize after extending volumes.
• Accommodates growing data needs.
• Uses tools like resize2fs.
  Resizing filesystems optimizes storage, ensuring available space is utilized without requiring new partitions or downtime.

78. Where are filesystem mount options defined?

Mount options are defined in /etc/fstab, specifying settings like noatime to reduce disk writes. This customizes mounting behavior, balancing performance and functionality for specific use cases in RHEL systems, ensuring efficient storage access.

79. Who can manage LVM physical volumes?

Root or sudo-privileged users manage LVM physical volumes, initializing disks for storage. This restricted access prevents accidental data loss, ensuring secure and efficient storage configuration for RHEL systems in enterprise environments.

80. Which command displays mounted filesystems?

• The findmnt command lists mounts.
• Shows devices and options.
• Verifies active filesystems.
  The findmnt command provides a clear overview, helping administrators manage and troubleshoot mounted filesystems effectively.

81. How do you reduce a logical volume size?

Reduce the filesystem size with resize2fs, then shrink the logical volume with lvreduce. Verify with lvs. This frees space for other volumes, maintaining data integrity while optimizing storage allocation in RHEL systems.

82. What does the vgcreate command do?

• Creates LVM volume groups.
• Groups physical volumes.
• Enables flexible storage.
  The vgcreate command organizes disks for logical volume allocation, supporting dynamic resizing and efficient storage management.

83. Why is the dumpe2fs command useful?

The dumpe2fs command displays ext2/ext3/ext4 filesystem details, like block size and inodes. It aids troubleshooting by providing metadata, ensuring administrators can verify configurations and maintain filesystem performance and integrity in RHEL environments.

84. When do you use the swapon command?

• Enables swap spaces.
• Provides virtual memory.
• Prevents system crashes.
  The swapon command activates swap partitions or files, ensuring stability during high memory usage for RHEL systems.

85. Where are LVM snapshots stored?

LVM snapshots reside within the volume group, using the same physical volumes. They are used for backups or testing, allowing administrators to capture volume states without disrupting operations, ensuring data protection in RHEL.

86. Who can mount a filesystem manually?

• Root or sudo-privileged users.
• Requires mount command access.
• Enables maintenance tasks.
  Manual mounting allows administrators to access filesystems for recovery or maintenance, ensuring secure storage operations.

87. Which command checks disk I/O performance?

The iostat command monitors disk I/O, showing read/write statistics. It identifies bottlenecks, helping optimize storage performance for heavy workloads, ensuring efficient operation of RHEL systems in demanding environments.

88. How do you create a new partition table?

Use parted to create a partition table, like GPT, and define partitions. This initializes disks for structured storage, enabling administrators to configure filesystems or swap spaces for RHEL systems, ensuring efficient resource allocation.

89. What is the purpose of the lvs command?

• Displays logical volume details.
• Shows size and volume group.
• Manages LVM configurations.
  The lvs command helps administrators monitor and manage storage resources, ensuring proper allocation in RHEL systems.

90. Why is the xfs_repair command used?

The xfs_repair command repairs XFS filesystems after crashes or corruption. It restores integrity, ensuring data accessibility and preventing loss in critical storage environments, maintaining reliable performance for RHEL systems.

Troubleshooting and Performance Tuning

91. What does the dmesg command display?

The dmesg command shows kernel ring buffer messages, like hardware or driver errors. It helps diagnose boot issues or system failures, providing insights into events affecting stability and performance in RHEL environments.

92. Why is the top command useful for performance monitoring?

• Shows real-time resource usage.
• Identifies CPU-intensive processes.
• Optimizes system performance.
  The top command helps administrators pinpoint resource-heavy tasks, ensuring efficient operation in multi-tasking RHEL systems.

93. When should you use the journalctl command?

Use journalctl to view systemd logs during troubleshooting. It analyzes service failures or errors, helping resolve issues quickly. This ensures system reliability by providing detailed event data for diagnosing problems in RHEL environments.

94. Where are kernel panic logs stored?

• Stored in /var/log/messages or /var/log/syslog.
• Contains crash details.
• Aids in diagnosing failures.
  Kernel panic logs help identify causes like hardware issues or kernel bugs, ensuring effective troubleshooting.

95. Who can modify kernel parameters at runtime?

Root or sudo-privileged users can modify kernel parameters with sysctl. This allows dynamic tuning, like enabling IP forwarding, optimizing performance or enabling specific functionalities without rebooting RHEL systems.

96. Which command checks network connectivity issues?

• The ping command tests connectivity.
• Measures latency and packet loss.
• Diagnoses network problems.
  The ping command ensures reliable communication, helping administrators verify network stability in RHEL systems.

97. How do you kill a hung process?

Identify the process ID with ps, use kill -9 to terminate it, and verify with ps. This stops unresponsive processes, freeing resources and restoring system stability without requiring a reboot in RHEL environments.

98. What is the purpose of the strace command?

• Traces system calls by processes.
• Diagnoses application failures.
• Identifies performance bottlenecks.
  The strace command shows process interactions, helping debug errors or optimize applications in RHEL systems.

99. Why is the sar command used?

The sar command collects performance data, like CPU or disk usage. It analyzes trends, helping administrators optimize resources and identify bottlenecks, ensuring efficient operation of RHEL systems under varying workloads.

100. When do you use the netstat command?

• Used in older RHEL versions.
• Lists network connections and ports.
• Troubleshoots network issues.
  The netstat command verifies service connectivity, ensuring applications run correctly in RHEL environments.

101. Where are systemd unit files stored?

Systemd unit files are in /etc/systemd/system for custom units and /usr/lib/systemd/system for defaults. They define service settings, allowing administrators to manage configurations and ensure proper service operation in RHEL systems.

102. Who can access performance tuning tools like tuned?

• Root or sudo-privileged users.
• Optimizes system performance.
• Adjusts workload-specific settings.
  The tuned tool enhances performance for specific workloads, ensuring optimal operation for RHEL servers or applications.

103. Which command monitors memory usage details?

The free command shows memory usage, including total, used, and free memory. It helps assess availability, identify shortages, and optimize resource allocation, ensuring efficient performance for processes in RHEL systems.

104. How do you troubleshoot a service failure?

• Check status with systemctl status.
• View logs with journalctl.
• Restart the service if needed.
  This identifies failure causes, like configuration errors, and restores functionality quickly in RHEL environments.

105. What does the lscpu command show?

• Displays CPU details.
• Shows cores and architecture.
• Verifies hardware capabilities.
  The lscpu command helps optimize performance for CPU-intensive tasks in RHEL systems.

106. Why is the iotop command useful?

The iotop command monitors disk I/O by process, identifying bottlenecks. It helps diagnose slow performance, ensuring efficient storage operations for heavy workloads in RHEL systems, maintaining system responsiveness.

107. When should you use the tcpdump command?

• Captures network packets.
• Analyzes traffic flow.
• Detects suspicious activity.
  The tcpdump command troubleshoots network issues, ensuring reliable performance and security in RHEL environments.

108. Where are core dump files stored?

Core dump files are in /var/lib/systemd/coredump or as configured in /proc/sys/kernel/core_pattern. They help diagnose application crashes, providing insights for debugging and resolving issues in RHEL systems.

109. Who can change the system hostname?

• Root or sudo-privileged users.
• Uses hostnamectl command.
• Ensures consistent identification.
  Changing the hostname ensures proper system identification across networks, critical for server management.

110. Which command checks system uptime?

The uptime command shows system runtime, helping verify stability and plan maintenance. It displays days or hours since the last reboot, ensuring minimal disruption to critical operations in RHEL environments.

111. How do you analyze disk performance with fio?

Install fio, run a test with specified parameters like block size and file size, and review IOPS or latency results. This tests disk speed, optimizing storage for specific workloads in RHEL systems.

112. What is the role of the /proc filesystem?

• Provides runtime system information.
• Includes /proc/cpuinfo for CPU details.
• Virtual filesystem for monitoring.
  The /proc filesystem helps troubleshoot and monitor resources without additional tools in RHEL.

113. Why is the nice command used?

The nice command adjusts process priority, ensuring critical tasks get more CPU time. It optimizes resource allocation, improving performance in multi-tasking RHEL environments where processes compete for system resources.

114. When do you use the lsof command?

• Lists open files by processes.
• Identifies resource conflicts.
• Aids in system diagnostics.
  The lsof command troubleshoots file or network issues, ensuring efficient resource management in RHEL.

115. Where are systemd journal logs stored?

Systemd journal logs are in /var/log/journal, providing detailed event data. They help troubleshoot service issues or security events, ensuring administrators can diagnose and resolve problems effectively in RHEL systems.

116. Who can update the system kernel?

• Root or sudo-privileged users.
• Uses dnf for updates.
• Requires reboot to apply.
  Kernel updates ensure security patches and new features, maintaining RHEL system reliability.

117. Which command monitors network interface traffic?

• The iftop command shows bandwidth usage.
• Monitors real-time traffic.
• Identifies high-traffic processes.
  The iftop command optimizes network performance and detects issues in RHEL systems.

118. How do you recover a deleted file in an ext4 filesystem?

Use extundelete to attempt recovery, targeting the specific file and partition. Immediate action is critical to avoid data overwrites. This helps restore accidentally deleted files, minimizing data loss in RHEL environments.

119. What does the vmstat command report?

• Reports memory, CPU, and I/O stats.
• Shows performance metrics.
• Identifies system bottlenecks.
  The vmstat command monitors performance, ensuring efficient resource utilization in RHEL systems.

120. Why is the tuned command used for performance?

The tuned command optimizes system settings for specific workloads, like throughput or latency. It adjusts CPU, disk, and network configurations, ensuring peak performance for servers or applications in RHEL environments.