RHCE Engineer Interview Questions with Answers [2025]

User and Group Management

1. What is the role of the /etc/passwd file in RHEL?

The /etc/passwd file stores user account details, including usernames, UIDs, GIDs, home directories, and shells. It ensures proper authentication and user environment setup, enabling secure access control and system functionality in RHEL enterprise environments.

2. Why is the usermod command essential for RHCE tasks?

• Modifies user attributes like UID or groups.
• Updates home directories or shells.
• Ensures secure account management.
  The usermod command allows precise account adjustments, aligning with organizational policies and maintaining security in RHEL multi-user systems.

3. When should you use the groupadd command?

Use groupadd during system setup or project collaboration to create groups for shared resource access. It assigns GIDs, enabling permission management, ensuring secure and organized access control in RHEL environments for efficient workflows.

4. Where are group memberships defined?

• Defined in /etc/group.
• Lists group names and members.
• Supports access control policies.
  Group memberships organize permissions, ensuring secure resource sharing in RHEL systems.

5. Who can manage user accounts?

Root or sudo-privileged administrators manage accounts using useradd or usermod. This ensures controlled account creation and modification, preventing unauthorized access and maintaining security in RHEL enterprise environments.

6. Which command shows group memberships?

• The id command displays user details.
• Lists primary and secondary groups.
• Verifies access permissions.
  It ensures correct group assignments for secure resource access in RHEL.

7. How do you lock a user account?

Use usermod -L username to lock an account, disabling login via /etc/shadow. Unlock with usermod -U. This temporarily restricts access, preserving data for security purposes in RHEL systems during administrative actions.

8. What does the /etc/login.defs file configure?

The /etc/login.defs file sets defaults for user creation, like password aging or UID ranges. It ensures consistent account policies, streamlining user management and enhancing security in RHEL multi-user environments.

9. Why is the visudo command preferred?

The visudo command validates /etc/sudoers syntax, preventing errors that could lock out administrators. It ensures secure privilege configuration, maintaining access control and system integrity in RHEL environments during administrative tasks.

10. When do you use the chage command?

• Sets password expiration policies.
• Configures account aging parameters.
• Enhances security compliance.
  Use chage to enforce password updates, reducing credential risks in RHEL systems.

11. Where are user-specific configurations stored?

• Stored in /home/username, e.g., .bashrc.
• Customizes shell or application settings.
• Ensures user-specific environments.
  These configurations provide personalized user experiences in RHEL systems.

12. Who can modify the /etc/sudoers file?

Root or sudo-privileged users edit /etc/sudoers using visudo. This ensures secure privilege delegation, preventing unauthorized actions and maintaining administrative control in RHEL systems for enterprise security.

13. Which command creates a new group?

The groupadd command creates groups, assigning GIDs for shared access. It simplifies permission management, ensuring secure resource allocation for collaborative projects in RHEL enterprise environments.

14. How do you add a user to a group?

Use usermod -aG groupname username to add a user to a group. Verify with id. This grants access to shared resources, ensuring secure collaboration in RHEL multi-user systems.

15. What is the /etc/gshadow file used for?

• Stores encrypted group passwords.
• Lists group administrators and members.
• Enhances group-level security.
  The /etc/gshadow file secures group access, ensuring authorized task execution in RHEL.

File and Directory Management

16. What does the chmod command do?

The chmod command modifies file or directory permissions, setting read, write, or execute rights. It ensures secure access control, restricting sensitive files to authorized users, critical for data integrity in RHEL systems.

17. Why is the chown command used?

• Changes file or directory ownership.
• Assigns users or groups.
• Enhances access control.
  The chown command ensures secure resource sharing in collaborative RHEL environments.

18. When should you use the find command?

Use find to locate files by name, size, or type during maintenance or troubleshooting. It streamlines file management, enabling quick identification for security or cleanup tasks in RHEL systems.

19. Where are temporary files stored?

• Stored in /tmp or /var/tmp.
• Used for transient data.
• Cleared periodically by system.
  Temporary files support short-term operations, ensuring efficient resource use in RHEL.

20. Who can change file permissions?

File owners or root/sudo-privileged users change permissions using chmod. This restricts access to authorized users, ensuring secure file management and preventing unauthorized modifications in RHEL systems.

21. Which command creates a symbolic link?

• The ln -s command creates symlinks.
• Links files or directories.
• Simplifies access without duplication.
  It enhances file management efficiency in RHEL systems.

22. How do you set Access Control Lists?

Use setfacl to set ACLs, granting specific permissions to users or groups. Verify with getfacl. This enables fine-grained access control, ensuring secure collaboration in RHEL environments.

23. What is the purpose of the tar command?

The tar command archives files or directories, creating compressed backups. It supports creating, extracting, or listing archives, ensuring efficient data storage and transfer for administrative tasks in RHEL systems.

24. Why is the getfacl command used?

• Displays Access Control Lists.
• Shows granular permissions.
• Verifies complex access settings.
  The getfacl command ensures precise access control in collaborative RHEL environments.

25. When do you use the rsync command?

Use rsync for efficient file synchronization or backups, copying only changed data. It supports remote transfers, ensuring data integrity and minimizing bandwidth usage in RHEL systems for reliable data management.

System Services and Processes

26. What does the systemctl command manage?

• Controls system services.
• Starts, stops, or enables services.
• Configures boot-time behavior.
  The systemctl command ensures service availability, critical for RHEL system reliability.

27. Why is the crontab command used?

The crontab command schedules automated tasks, like backups or updates, at defined intervals. It reduces manual effort, ensuring consistent execution of repetitive tasks, enhancing efficiency in RHEL system administration.

28. When should you restart a service?

• Restart after configuration changes.
• Apply updates or patches.
• Resolve service failures.
  Restarting ensures services reflect new settings, maintaining functionality in RHEL systems.

29. Where are systemd unit files stored?

• Custom units in /etc/systemd/system.
• Defaults in /usr/lib/systemd/system.
• Defines service configurations.
  Unit files manage service settings, ensuring proper operation in RHEL systems.

30. Who can manage system services?

Root or sudo-privileged users manage services using systemctl. This ensures controlled operations, preventing unauthorized changes and maintaining system stability in RHEL enterprise environments.

31. Which command monitors running processes?

• The ps command lists processes.
• Shows PIDs and resource usage.
• Aids performance management.
  It ensures efficient task management in RHEL systems.

32. How do you prioritize a process?

Use nice to set priority for new processes or renice for running ones. This allocates CPU resources effectively, ensuring critical tasks perform optimally in RHEL systems under varying workloads.

33. What is the role of the top command?

• Displays real-time resource usage.
• Shows CPU and memory stats.
• Identifies resource-intensive processes.
  The top command optimizes performance in multi-tasking RHEL environments.

34. Why is the kill command used?

The kill command terminates processes using signals like SIGTERM or SIGKILL. It frees resources from hung processes, restoring system stability without rebooting, critical for efficient RHEL system management.

35. When do you use the lsof command?

• Lists open files by processes.
• Identifies resource conflicts.
• Aids troubleshooting tasks.
  Use lsof to diagnose file or network issues in RHEL systems.

Security and Access Control

36. What is the purpose of the /etc/sudoers file?

The /etc/sudoers file defines user privileges for executing commands with elevated permissions. Edited with visudo, it ensures controlled administrative access, preventing unauthorized actions and maintaining security in RHEL systems.

37. Why is SELinux critical for security?

• Enforces mandatory access controls.
• Restricts process privileges.
• Mitigates exploit risks.
  SELinux limits unauthorized actions, ensuring processes adhere to policies, enhancing security in RHEL environments.

38. When should you use the semanage command?

Use semanage to manage SELinux policies, like file contexts or ports. It ensures applications comply with security constraints, enabling secure operation in RHEL without disabling SELinux protections.

39. Where are failed login attempts logged?

• Logged in /var/log/secure or /var/log/auth.log.
• Shows user and failure details.
• Detects brute-force attacks.
  Monitoring logs ensures timely security responses in RHEL systems.

40. Who can configure SSH access?

Root or sudo-privileged administrators configure SSH via /etc/ssh/sshd_config. They manage settings like ports or authentication, ensuring secure remote access for authorized users in RHEL environments.

41. Which command lists open network ports?

• The ss command shows open ports.
• Lists TCP/UDP connections.
• Verifies service accessibility.
  It minimizes security risks in RHEL network configurations.

42. How do you enable SELinux enforcing mode?

Edit /etc/selinux/config to set SELINUX=enforcing, apply with setenforce 1, and reboot if needed. This enforces strict policies, enhancing security by preventing unauthorized actions in RHEL systems.

43. What does the restorecon command do?

• Resets SELinux file contexts.
• Ensures policy compliance.
• Prevents service denials.
  The restorecon command corrects contexts, maintaining security in RHEL environments.

44. Why disable root login via SSH?

Disabling root SSH login in /etc/ssh/sshd_config reduces attack risks, forcing standard user logins with sudo. This minimizes damage from compromised credentials, enhancing security in RHEL networked systems.

45. When do you use the auditctl command?

• Configures real-time auditing.
• Monitors critical file changes.
• Ensures security compliance.
  The auditctl command tracks sensitive modifications, maintaining accountability in RHEL systems.

Storage and Filesystem Management

46. What is the purpose of the mkfs command?

The mkfs command formats partitions to create filesystems, like ext4 or XFS, preparing storage for data. It enables administrators to configure disks for specific use cases, ensuring compatibility in RHEL systems.

47. Why is Logical Volume Manager (LVM) used?

• Supports dynamic volume resizing.
• Simplifies storage allocation.
• Enhances flexibility.
  LVM allows storage adjustments without downtime, optimizing resources in RHEL environments.

48. When should you use the fsck command?

• Checks filesystem integrity.
• Repairs errors post-crash.
• Runs on unmounted filesystems.
  The fsck command ensures reliable storage, preventing data corruption in RHEL.

49. Where are swap spaces defined?

• Defined in /etc/fstab.
• Lists swap devices or files.
• Provides virtual memory.
  Swap spaces ensure stability during high memory usage in RHEL.

50. Who can create logical volumes?

Root or sudo-privileged users create logical volumes, ensuring secure storage management. This prevents unauthorized changes, optimizing disk usage in RHEL systems for enterprise-grade solutions.

51. Which command shows disk usage?

• The du command lists directory sizes.
• Uses human-readable format.
• Identifies large directories.
  It optimizes storage and plans cleanup in RHEL systems.

52. How do you extend a logical volume?

Use lvextend to increase volume size, resize the filesystem with resize2fs, and verify with lvs. This expands storage dynamically, supporting growing data needs in RHEL without disruptions.

53. What does the parted command do?

• Manages disk partitions.
• Supports large disk sizes.
• Configures partition tables.
  The parted command enables flexible storage setups in RHEL systems.

54. Why is the mount command important?

The mount command integrates filesystems into the directory tree, enabling data access. It connects devices to mount points, ensuring applications or users access required data in RHEL systems.

55. When do you use the blkid command?

• Displays block device attributes.
• Shows UUIDs and types.
• Aids /etc/fstab setup.
  The blkid command ensures accurate filesystem mounting in RHEL systems.

Networking Configuration

56. What does the /etc/hosts file do?

The /etc/hosts file maps IPs to hostnames for local resolution. It supports fast, DNS-independent communication, essential for small networks or reliable hostname mappings in RHEL systems.

57. Why is the nmcli command used?

• Manages network configurations.
• Sets static IPs or connections.
• Automates network tasks.
  The nmcli command ensures reliable connectivity for RHEL servers, ideal for scripting.

58. When should you restart networking?

Restart networking after configuration changes, like IP updates, using nmcli con reload. This applies settings without rebooting, ensuring continuous connectivity for critical services in RHEL production environments.

59. Where are DNS settings configured?

• Configured in /etc/resolv.conf.
• Managed via NetworkManager tools.
• Specifies DNS servers.
  DNS settings ensure reliable name resolution in RHEL systems.

60. Who can configure network interfaces?

Root or sudo-privileged administrators configure interfaces using nmcli or manual edits. This ensures secure network setup, preventing unauthorized changes and maintaining connectivity in RHEL systems.

61. Which command checks network connectivity?

• The ping command tests connectivity.
• Measures latency and packet loss.
• Diagnoses network issues.
  It ensures reliable communication in RHEL systems.

62. How do you set a static IP address?

Edit /etc/sysconfig/network-scripts/ifcfg-<interface>, set BOOTPROTO=none, specify IPADDR, NETMASK, and GATEWAY. Restart with nmcli con reload. This ensures stable connectivity for RHEL servers.

63. What is the purpose of the /etc/resolv.conf file?

The /etc/resolv.conf file lists DNS servers for name resolution. Managed by NetworkManager, it ensures applications resolve hostnames reliably, critical for network-dependent services in RHEL systems.

64. Why is the firewall-cmd command used?

• Manages firewalld rules.
• Opens or closes ports.
• Ensures secure network access.
  The firewall-cmd command supports dynamic changes in RHEL production environments.

65. When do you use the ip command?

Use the ip command to manage interfaces, routes, or addresses. It replaces ifconfig, providing advanced control for configuring and troubleshooting networks in RHEL systems efficiently.

Advanced System Administration

66. What is the purpose of the tuned service?

The tuned service optimizes performance by adjusting CPU or disk settings based on workload profiles. It enhances efficiency, ensuring RHEL systems meet specific performance requirements in enterprise environments.

67. Why is the ansible tool used?

• Automates configuration management.
• Streamlines system administration tasks.
• Ensures consistent deployments.
  The ansible tool simplifies large-scale RHEL system management, enhancing efficiency and reliability.

68. When should you use the puppet tool?

Use puppet for automating configuration management in large RHEL environments. It ensures consistent settings across servers, reducing manual effort and maintaining compliance with organizational policies.

69. Where are kernel modules stored?

• Stored in /lib/modules/<kernel-version>.
• Supports hardware or filesystems.
• Enables new features.
  Kernel modules ensure compatibility and functionality in RHEL systems.

70. Who can update the system kernel?

Root or sudo-privileged users update the kernel with dnf, applying patches and features. A reboot ensures updates take effect, maintaining reliability in RHEL enterprise environments.

71. Which command loads a kernel module?

• The modprobe command loads modules.
• Resolves module dependencies.
• Enhances system functionality.
  It enables dynamic feature addition in RHEL systems.

72. How do you configure a Red Hat cluster?

Use pcs to set up nodes, resources, and fencing. Configure /etc/corosync/corosync.conf for communication. This ensures high availability, supporting critical services in RHEL environments with minimal downtime.

73. What is the role of the subscription-manager?

The subscription-manager registers RHEL systems with Red Hat for updates and support. It manages subscriptions, ensuring access to repositories, patches, and security advisories, critical for enterprise compliance.

74. Why is the cockpit tool used?

• Provides web-based system management.
• Monitors performance and services.
• Simplifies administrative tasks.
  The cockpit tool enhances RHEL system administration with an intuitive interface.

75. When do you use the sosreport command?

Use sosreport to collect system diagnostics for troubleshooting. It gathers logs, configurations, and performance data, aiding support teams in diagnosing issues, ensuring quick resolution in RHEL environments.

76. Where are subscription details stored?

• Stored in /etc/rhsm/rhsm.conf.
• Includes subscription server details.
• Manages repository access.
  Subscription details ensure update availability in RHEL systems.

77. Who can configure high-availability clusters?

Root or sudo-privileged administrators configure clusters using pcs. This ensures secure setup of high-availability services, maintaining uptime and reliability for critical applications in RHEL environments.

78. Which command manages software packages?

• The dnf command installs/updates packages.
• Resolves dependencies automatically.
• Ensures system updates.
  It maintains security and functionality in RHEL systems.

79. How do you back up a RHEL system?

Use rsync for file backups, tar for archives, or rear for system recovery. Schedule with cron for automation. This ensures data protection and quick restoration in RHEL environments.

80. What does the httpd service do?

The httpd service runs the Apache web server, hosting websites or applications. It supports secure configurations with HTTPS, ensuring reliable web services in RHEL environments for enterprise applications.

81. Why is the sssd service used?

• Integrates with LDAP or Active Directory.
• Manages centralized authentication.
• Caches credentials for offline access.
  The sssd service ensures secure user authentication in RHEL enterprise environments.

82. When do you use the chronyd service?

Use chronyd to synchronize system time with NTP servers. It ensures accurate timekeeping, critical for logging, authentication, and scheduled tasks in RHEL systems, especially in distributed environments.

83. Where are Apache configuration files stored?

• Stored in /etc/httpd/conf.
• Includes httpd.conf for main settings.
• Supports virtual host configurations.
  These files ensure flexible web server management in RHEL systems.

84. Who can configure the httpd service?

Root or sudo-privileged administrators configure the httpd service, managing web server settings. This ensures secure and reliable web hosting for applications in RHEL enterprise environments.

85. Which command manages SELinux booleans?

• The setsebool command sets booleans.
• Enables specific SELinux policies.
• Supports service functionality.
  It ensures secure application operations in RHEL systems.

86. How do you set up a virtual host in Apache?

Edit /etc/httpd/conf.d/vhost.conf, define VirtualHost with domain and document root, and restart httpd. This hosts multiple websites on one server, ensuring efficient resource use in RHEL environments.

87. What is the purpose of the named service?

The named service runs BIND, providing DNS resolution. It supports local or authoritative DNS, ensuring reliable name resolution for network services in RHEL enterprise environments.

88. Why is the postfix service used?

• Manages email delivery.
• Supports SMTP protocols.
• Ensures reliable mail services.
  The postfix service enables secure email communication in RHEL systems.

89. When do you use the samba service?

Use samba for file and printer sharing with Windows systems. It enables cross-platform integration, ensuring seamless resource access in mixed RHEL and Windows environments.

90. Where are NFS configuration files stored?

• Stored in /etc/exports.
• Defines NFS share settings.
• Controls client access.
  These files ensure secure file sharing in RHEL systems.

91. Who can configure the named service?

Root or sudo-privileged administrators configure the named service, managing DNS settings. This ensures secure and reliable name resolution for network services in RHEL enterprise environments.

92. Which command manages NFS exports?

• The exportfs command manages exports.
• Updates NFS share configurations.
• Ensures client access.
  It maintains secure file sharing in RHEL systems.

93. How do you secure an Apache web server?

Configure HTTPS in /etc/httpd/conf.d/ssl.conf, enable SSL, and restrict access with .htaccess. This ensures encrypted connections and secure access control for web services in RHEL environments.

94. What does the iptables command do in older RHEL?

• Configures firewall rules.
• Filters network traffic.
• Secures system communications.
  The iptables command protected legacy RHEL systems from unauthorized access.

95. Why is the firewall-cmd command used?

• Manages firewalld rules.
• Opens or closes ports.
• Ensures secure network access.
  The firewall-cmd command supports dynamic changes in RHEL production environments.

96. When do you use the semanage fcontext command?

Use semanage fcontext to set SELinux file contexts for custom paths. It ensures applications comply with security policies, enabling secure operation in RHEL without disabling SELinux.

97. Where are postfix configuration files stored?

• Stored in /etc/postfix.
• Includes main.cf for settings.
• Manages email delivery.
  These files ensure reliable mail services in RHEL systems.

98. Who can configure the samba service?

Root or sudo-privileged administrators configure samba, managing file and printer sharing. This ensures secure cross-platform integration in RHEL and Windows mixed environments.

99. Which command monitors network traffic?

• The iftop command shows bandwidth usage.
• Identifies high-traffic processes.
• Optimizes network performance.
  It ensures reliable communication in RHEL systems.

100. How do you configure an NFS share?

Edit /etc/exports, specify share paths and client permissions, and run exportfs -ra. Restart nfs-server. This enables secure file sharing with remote clients in RHEL environments.

101. What is the role of the /etc/exports file?

The /etc/exports file defines NFS shares, specifying directories and client access permissions. It ensures secure and controlled file sharing, enabling remote access for authorized clients in RHEL systems.

102. Why is the chronyc command used?

• Manages chronyd time synchronization.
• Queries NTP server status.
• Ensures accurate timekeeping.
  The chronyc command supports logging and authentication in RHEL systems.

103. When do you use the smbpasswd command?

Use smbpasswd to manage Samba user passwords for file sharing. It ensures secure authentication, enabling seamless access to shared resources in mixed RHEL and Windows environments.

104. Where are samba configuration files stored?

• Stored in /etc/samba/smb.conf.
• Defines share and authentication settings.
• Supports cross-platform integration.
  These files ensure secure file sharing in RHEL systems.