Sysadmin Interview Questions That Actually Matter

The interview questions you’re preparing for probably aren’t the ones that will determine whether you get the job.

You’ve memorized the OSI model. You can recite the DORA process for DHCP. You know what ports SSH, HTTP, and DNS use. That’s expected—it’s table stakes. Every candidate who makes it to a sysadmin interview knows the basics.

What separates the hired candidates from the rejected ones isn’t trivia recall. It’s how they think through problems. Can they troubleshoot a scenario they’ve never seen before? Do they understand why systems work, not just what they do? Can they explain technical concepts to someone who isn’t technical?

This guide skips the easily-Googleable definitions and focuses on the questions that actually reveal whether someone can do the job. If you’re preparing for a sysadmin interview, these are the questions that matter—and how to approach them without memorizing scripts.

The Two Categories That Decide Everything

Sysadmin interviews split into two buckets: technical questions and scenario-based questions. Most candidates over-prepare for the first and under-prepare for the second.

Technical questions test your knowledge. What’s a subnet mask? How does DNS resolution work? What’s the difference between TCP and UDP? These have correct answers, and either you know them or you don’t.

Scenario questions test your thinking. A server went down at 2 AM—walk me through how you’d troubleshoot it. A user can’t access a network share—where do you start? These don’t have single correct answers. They reveal your methodology, your prioritization, and whether you’ve actually done this work before.

Interviewers weight scenario questions more heavily. Anyone can study definitions. Fewer people can think through problems under pressure while explaining their reasoning clearly.

Technical Questions That Go Beyond Definitions

The following questions appear frequently in sysadmin interviews. But notice how each one invites follow-up—the initial question is just the door; the conversation behind it is what matters.

Networking Fundamentals

“Explain the difference between TCP and UDP. When would you choose one over the other?”

The definition part is easy: TCP is connection-oriented with guaranteed delivery; UDP is connectionless without delivery guarantees.

What makes your answer strong is connecting this to real scenarios. TCP makes sense for anything requiring reliable delivery—file transfers, email, web traffic. UDP makes sense when speed matters more than guaranteed delivery—DNS queries, video streaming, VoIP. If you’ve studied networking fundamentals, you can go deeper into how each protocol handles packet loss and ordering.

The interviewer might follow up: “What happens if you try to stream video over TCP instead of UDP?” Good candidates can explain the retransmission overhead and why buffering issues would result.

“A user reports they can’t access a website. Walk me through your troubleshooting process.”

This is actually three questions disguised as one: Can you troubleshoot? Do you follow a logical process? Can you explain it?

Start simple: Can they reach other websites? If not, the problem is broader than one site. If yes, the problem is specific to that site. Next: ping the site’s IP address directly. If that works but the hostname doesn’t, you’ve identified a DNS issue. Check DNS configuration. If ping fails entirely, check routing, firewalls, and whether the site is actually down.

Good answers demonstrate systematic thinking—starting from the user, narrowing down possibilities, and not jumping to conclusions. Mention that you’d check if other users are affected before assuming it’s a client-side problem.

“What is DHCP and why do organizations use it?”

Beyond the definition (Dynamic Host Configuration Protocol assigns IP addresses automatically), explain the actual value: manual IP assignment doesn’t scale. A network with 500 devices can’t have someone manually tracking and assigning addresses. DHCP centralizes that management.

If you understand DHCP deeply, you can discuss scopes, leases, reservations, and what happens when a DHCP server goes down. Interviewers often follow up with: “What problems can occur with DHCP?” Good answers include IP exhaustion, duplicate addresses from rogue DHCP servers, and lease expiration issues.

Linux Administration

“A server is running slowly. How would you diagnose the problem?”

This tests whether you have a troubleshooting methodology or just throw commands at the wall.

Start with resource utilization: top or htop to see CPU, memory, and which processes consume them. df -h to check disk space. iostat or iotop for disk I/O bottlenecks. netstat or ss for network connections.

Explain why each step matters. High CPU usage by a specific process tells you where to look. Full disks cause all kinds of strange behavior. Memory pressure leads to swapping, which kills performance. The goal is narrowing down which resource is constrained.

Candidates who have actually done this work mention checking logs (/var/log/messages, application-specific logs) and recent changes (new deployments, configuration updates, cron jobs running).

“What’s the difference between hard links and symbolic links?”

Hard links point to the same inode—they’re essentially different names for the same file data. Deleting the “original” file doesn’t affect a hard link because both point to the same underlying data. Hard links can’t span filesystems or link to directories.

Symbolic links (symlinks) are pointers to file paths. If you delete the original file, the symlink becomes broken. Symlinks can span filesystems and link to directories.

Practical follow-up: “When would you use each?” Hard links for creating backup references to important files. Symlinks for creating shortcuts, managing application versions, or pointing to files on different partitions.

“How would you find all files larger than 100MB that were modified in the last 7 days?”

find / -type f -size +100M -mtime -7

But explaining the command shows deeper understanding. -type f means files only. -size +100M means larger than 100 megabytes. -mtime -7 means modified within the last 7 days. Know how to combine with -exec to do something with those files.

Practice command line skills until this feels natural. Interviewers can tell when someone is reciting memorized commands versus actually using them.

Windows Administration

“Explain what Active Directory is and why organizations use it.”

Active Directory is Microsoft’s directory service for managing network resources—users, computers, groups, policies. But why does this matter?

Centralization. Without AD, every computer manages its own user accounts, passwords, and permissions. With AD, a single change propagates everywhere. You create a user once; they can log into any domain-joined computer. You set a password policy once; it applies across the organization.

If you’ve worked with AD, mention specific experiences: Group Policy management, OU structure design, user provisioning, or troubleshooting login issues. Practical experience beats textbook knowledge.

“A user’s account is locked out. How do you troubleshoot?”

Unlock the account (easy). But find out why it locked—that’s the real job.

Check Event Viewer on domain controllers for failed logon attempts. Look at the source IP to identify which device is sending bad credentials. Common causes: user forgot password and kept trying, old password cached on mobile device, scheduled task with outdated credentials, mapped drive with saved credentials. Understanding Active Directory structure helps you know where to look.

Tools like Microsoft’s Account Lockout and Management Tools (LockOutStatus.exe) help trace the source. If you’ve dealt with persistent lockouts, you know how frustrating they are to track down. Mention that experience.

“What’s the difference between a domain, a tree, and a forest in Active Directory?”

A domain is a logical container for network objects sharing a common namespace and security policies. A tree is a collection of domains in a contiguous namespace hierarchy (parent-child relationships). A forest is a collection of one or more trees that share a common schema and global catalog.

The practical implication: trust relationships. Domains within a tree automatically trust each other. Forests can be configured to trust each other, but it’s not automatic. This matters when organizations merge or need to separate security boundaries.

Virtualization and Cloud

“Explain the benefits of virtualization.”

Hardware consolidation (multiple VMs on one physical server), easier disaster recovery (VM snapshots, replication), faster provisioning (clone a template instead of building from scratch), better resource utilization (allocate resources dynamically).

If you’ve worked with VMware, Hyper-V, or KVM, mention specific experiences. Setting up a home lab with virtualization demonstrates hands-on skills that studying alone doesn’t prove.

“What’s the difference between IaaS, PaaS, and SaaS?”

Infrastructure as a Service: you manage OS and applications; provider manages physical hardware and virtualization. Examples: AWS EC2, Azure VMs.

Platform as a Service: you manage applications; provider manages OS, runtime, and infrastructure. Examples: Heroku, AWS Elastic Beanstalk. If you’re interested in this space, explore cloud career paths.

Software as a Service: provider manages everything; you just use the application. Examples: Gmail, Salesforce, Microsoft 365.

The follow-up question often probes whether you understand when to use each. SaaS for standard business applications (email, CRM). PaaS for development when you don’t want to manage infrastructure. IaaS when you need full control over the environment.

Scenario Questions: Where Interviews Are Won or Lost

These questions have no single correct answer. Interviewers evaluate your thinking process, prioritization, and communication clarity.

”A production server went down at 2 AM. Walk me through your response.”

This tests incident response methodology.

First priority: assess impact. Is it a critical system? Are users affected right now? This determines urgency level. Then verify the problem—is the server actually down, or is monitoring giving false positives? Can you ping it? Can you SSH/RDP into it?

Next: gather information. Check recent changes. Look at monitoring dashboards. Review logs if accessible. Contact whoever might have made changes.

Then troubleshoot based on symptoms. Hardware failure? OS crash? Service failure? Network issue? Your approach depends on what you find.

Throughout, communicate status. Let stakeholders know you’re working on it and provide estimated updates. Document everything for the post-incident review.

Good answers include specific tools: monitoring platforms (Nagios, Zabbix, Datadog), IPMI/iLO for out-of-band access, centralized logging systems. If you understand Wireshark for packet analysis, mention it when discussing network troubleshooting.

”A user complains their computer is running slowly. How do you approach this?”

Resist the urge to jump into solutions. Ask clarifying questions first.

When did it start? Was anything installed or changed recently? Is it slow all the time or during specific activities? These questions often reveal the cause before you touch the machine.

If you need to investigate: check Task Manager for resource usage. Look for obvious culprits—browser with 50 tabs, background updates, antivirus scanning. Check startup programs. Review recently installed software.

What makes answers good: acknowledging that “slow” means different things to different users. A computer that takes 30 seconds to boot might be “slow” to one user and normal to another. Managing expectations is part of the job.

”How would you migrate email from an on-premises Exchange server to Microsoft 365?”

This tests planning and migration experience.

A complete answer touches on: assessment (how many mailboxes, how much data, any compliance requirements), coexistence (running both systems during migration), cutover versus staged migration, DNS changes (MX records), user communication, testing, and rollback planning. Knowing how to document IT processes is valuable here.

You don’t need to have done this specific migration. But demonstrating that you’d research thoroughly, plan carefully, test before committing, and communicate with users shows the mindset organizations want.

”A backup job has been failing for three days. No one noticed until now. What do you do?”

This tests prioritization under pressure.

Immediate concern: are critical backups affected? What’s the recovery point situation? If this is a database server without valid backups, that’s an emergency.

Investigation: check backup logs for error messages. Disk space full? Network connectivity to backup target failed? Credential expired? Backup software license issue? Each error points to a different fix.

Prevention: why didn’t anyone notice for three days? Monitoring should alert on backup failures. This incident is also an opportunity to improve monitoring and alerting.

The question tests whether you think about both the immediate fix and the systemic improvement.

Behavioral Questions for Sysadmins

Technical skills get you in the door. Soft skills determine whether you fit the team.

”Tell me about a time you had to explain a technical problem to a non-technical stakeholder.”

The ability to translate technical concepts matters enormously. Not everyone understands that “DNS propagation” is why the website change hasn’t shown up everywhere yet.

Good answers demonstrate empathy—you understood what the stakeholder actually needed to know (not everything, just what’s relevant) and explained it without condescension. If you’ve practiced explaining tech to non-technical people, reference specific techniques.

”Describe a significant system failure you dealt with. What happened and what did you learn?”

Interviewers want to hear about real problems, not sanitized versions where everything went perfectly.

Strong answers acknowledge what went wrong, what you did to fix it, and—critically—what you did to prevent recurrence. The “what did you learn” part matters most. If the same problem happened again, would you handle it differently? Did you implement monitoring, automation, or documentation to prevent it?

Use the STAR method: Situation, Task, Action, Result. Structure keeps your answer focused.

”How do you stay current with technology changes?”

This field changes constantly. Sysadmins who stopped learning five years ago have stale skills. If you’re already thinking about DevOps transitions, that’s worth mentioning.

Mention specific resources: subreddits like r/sysadmin, podcasts, blogs, certification study, home labs, professional communities. If you’re working toward certifications, mention them. If you run a home lab to test new technologies, that demonstrates initiative.

But be honest. If your real answer is “I learn when I encounter problems at work,” that’s valid too—as long as you’re genuinely solving problems and not just coasting.

Questions to Ask Your Interviewer

Interviews are bidirectional. Your questions reveal what you value and whether you’ve thought about the role.

Strong questions:

• “What does a typical day look like for this role?” (Reveals actual workload)
• “How does the team handle on-call rotations?” (Shows you understand the reality)
• “What’s the biggest technical challenge the team is facing?” (Demonstrates interest in real problems)
• “How do you handle change management for production systems?” (Shows process awareness)
• “What happened to the last person in this role?” (Can reveal red flags or growth opportunities)

Questions to avoid:

• Anything you could find on the company website
• Salary and benefits (save for HR discussions)
• “What do you do here?” (You should already know this)

Preparation That Actually Helps

Build a Home Lab

Nothing substitutes for hands-on experience. Set up VirtualBox or Proxmox, install Windows Server and Linux VMs, configure Active Directory, break things on purpose, fix them. When an interviewer asks about troubleshooting, you’ll have real scenarios to reference.

Practice command-line skills with Shell Samurai—interactive exercises build the muscle memory you need when someone asks “how would you find all files modified in the last 24 hours?”

Know Your Resume

Every line on your resume is fair game. If you listed “managed backup systems,” be ready to explain what software, how many servers, and what your backup strategy was. If you can’t speak to something in detail, don’t list it.

Practice Out Loud

Technical interviews require explaining your thinking. That’s different from knowing the answer silently. Practice answering questions out loud—to a friend, to your cat, to a recording. The first time you verbalize a troubleshooting approach shouldn’t be in the interview.

Research the Company’s Tech Stack

If the job posting mentions specific technologies, know them. Running Windows Server 2022? Review the new features in our Windows Server tutorial. Using Azure? Understand the basics of their cloud services. Using Ansible for automation? Check our Ansible guide for a refresher.

Quick Reference: Common Questions by Category

Category	Example Questions
Networking	TCP vs UDP, subnetting, DNS resolution, firewall rules, VLAN concepts
Linux	File permissions, process management, log analysis, package management, cron
Windows	Active Directory, Group Policy, NTFS permissions, Windows services, PowerShell
Virtualization	VM snapshots, resource allocation, hypervisor types, migration strategies
Security	User authentication, encryption basics, security policies, patch management
Troubleshooting	Server down scenarios, slow performance, connectivity issues, user problems

Frequently Asked Questions

How technical should my answers be?

Match the interviewer. If they have a technical background (another sysadmin or IT manager), go deep. If they’re from HR, stay conceptual. When in doubt, start with a summary and offer to go deeper: “The short answer is DNS. Would you like me to walk through the technical details?”

What if I don’t know the answer to a question?

Don’t fake it. “I haven’t worked with that technology directly, but here’s how I’d approach learning it” is better than an obviously made-up answer. Interviewers respect honesty and problem-solving orientation over pretended expertise.

Should I mention my home lab or personal projects?

Absolutely. A home lab demonstrates initiative, curiosity, and hands-on experience that job duties alone might not provide. Be ready to describe what you’ve built and what you learned from it.

How long should my answers be?

Long enough to demonstrate competence, short enough to stay focused. For technical questions, 30 seconds to 2 minutes. For scenario questions, 2-4 minutes. Watch for cues—if the interviewer looks ready to move on, wrap up.

What’s the biggest mistake candidates make?

Not asking clarifying questions on scenario problems. When an interviewer says “a server is down,” ask: which server, what symptoms, what’s the impact? Jumping straight to solutions without gathering information mirrors how inexperienced admins approach real problems.

Final Thoughts

The sysadmin interview isn’t about proving you’ve memorized every command and protocol. It’s about demonstrating that you can think through problems systematically, communicate clearly, and learn what you don’t already know.

Technical knowledge is the baseline. Everyone who interviews has studied the basics. What sets candidates apart is showing how they apply that knowledge—the troubleshooting methodology, the attention to impact and priority, the ability to explain complex concepts simply.

Prepare by doing, not just reading. Build systems. Break things. Fix them. That experience gives you stories to tell and confidence that shows.

The next interview you walk into, you won’t just know the answers—you’ll understand why those answers matter.