Linux Interview Questions and Answers for experienced
Linux Admin Interview Questions: The Linux operating system is widely used in servers, mainframes, databases and more due to its stability, security and flexibility. As a result, Linux admin roles are in high demand. Passing the Linux admin interview requires strong technical knowledge and skills. This article provides an overview of common Linux admin interview questions and example answers.
Linux Admin Interview Questions About System Configuration
Some typical Linux admin interview questions that assess your skills in system configuration include:
What are the key files to configure network interfaces in Linux?
The two main files for network interface configuration in Linux are /etc/sysconfig/network-scripts/ifcfg-ethX (where X is the interface number) for CentOS/RHEL, and /etc/network/interfaces for Debian/Ubuntu. These files allow setting the IP address, subnet mask, gateway and other network parameters for an interface.
How do you manage runlevels and services in Linux?
Runlevels determine which services are started at boot time. The main tools for managing runlevels and services are init, systemd (on newer distros) and tools like chkconfig or update-rc.d. For example,
chkconfig --list lists services for each runlevel, while
chkconfig httpd on enables the httpd service.
What is SSH and how do you troubleshoot SSH connection issues?
SSH (Secure Shell) allows logging into and managing a remote Linux machine securely. If SSH fails, some troubleshooting steps include confirming the SSH daemon is running on the target machine, verifying firewall rules allow port 22 connections, checking SSH client config and troubleshooting authentication issues.
Linux Admin Interview Questions About Security
Some example security-focused questions include:
How do you manage Linux user accounts and permissions?
User accounts can be managed with commands like adduser, addgroup and passwd. File/folder permissions can be viewed using ls -la and modified with chmod/chown. Useful permissions include 755 for directories and 644 for files. Properly setting permissions and using ACLs helps secure the system.
What steps would you take to secure a new Linux server?
Some best practices include disabling root login over SSH, using sudo for privilege escalation, enabling the firewall, closing unused ports, applying OS updates/patches, configuring log monitoring, disabling unused services, setting up SSH key authentication, and creating non-root user accounts for admins.
What Linux security tools are you familiar with?
Useful open-source security tools include nmap for port scanning, nessus for vulnerability scanning, Nagios for system monitoring, OSSEC for host intrusion detection, Tripwire for change detection, and tools like ps, top and lsof for monitoring processes and open files.
Linux Admin Interview Questions About Troubleshooting
Example troubleshooting questions include:
How would you troubleshoot a Linux system that suddenly runs slowly?
I would check system resource usage with tools like top/htop, vmstat and iostat to identify any CPU, memory, disk or network bottlenecks. I would also check logs for errors and inspect running processes/services to identify any culprits.
What steps would you take to troubleshoot a 500 Internal Server Error for a web application on Linux?
I would first check the web server error log and application logs for any errors. I would confirm the application is running, verify permissions on application directories, check system resource usage, restart services, check for configuration issues, test connectivity to backend resources like the database, and reproduce the error to isolate the cause.
How do you identify the cause of a Linux system that suddenly reboots or crashes?
I would check syslog and kernel logs in /var/log for relevant entries preceding a reboot/crash like hardware errors, kernel panics or out of memory errors. I would also monitor system health with tools like top and vmstat to identify high load, memory usage or other factors that could cause system instability.
Mastering common Linux admin interview questions demonstrates your technical skills and experience to excel as a Linux system administrator. Be prepared to answer questions about system configuration, security, troubleshooting and more. Show your expertise in Linux administration and you will ace the interview!