Interview questions and answers
Linux
- What is the difference between a hard link and a soft link? — easy
- How do you find which process is listening on a port? — easy
- Explain the permission string -rwxr-x---. — easy
- What do the setuid, setgid and sticky bits do? — medium
- What is load average and how do you read it? — medium
- A disk is full but du shows little usage. Why? — medium
- What is the difference between kill -15 and kill -9? — medium
- How do you search recursively for a string in files? — easy
- Describe the Linux boot process. — hard
- What is a zombie process? — medium
RHCSA
- How do you reset a forgotten root password on RHEL 9? — easy
- How do you create a logical volume and mount it persistently? — medium
- How do you extend an XFS logical volume? — medium
- A web server cannot read files in a custom directory with SELinux enforcing. How do you fix it? — medium
- How do you open a port permanently with firewalld? — easy
- How do you schedule a recurring job for a user? — medium
- How do you set a static IP with nmcli? — easy
- How do you configure a collaborative directory for a group? — medium
- How do you make the system boot into a non-graphical target? — medium
- How do you add swap space persistently? — easy
DevOps
- What is CI/CD? — easy
- What is the difference between blue-green and canary deployments? — medium
- What is infrastructure as code and why use it? — medium
- Declarative vs imperative configuration? — medium
- What does idempotent mean in configuration management? — easy
- How should secrets be handled in a pipeline? — medium
- What are the four golden signals of monitoring? — medium
- What are SLI, SLO and SLA? — hard
- What is the purpose of a Git branching strategy? — easy
- What is configuration drift and how do you prevent it? — medium
Docker
- What is the difference between an image and a container? — easy
- CMD vs ENTRYPOINT? — easy
- How do you reduce Docker image size? — medium
- Volumes vs bind mounts? — medium
- How does layer caching work during a build? — medium
- COPY vs ADD? — easy
- Which Linux kernel features make containers possible? — medium
- How do containers on the same host talk to each other? — medium
- Why should containers not run as root? — hard
- What does docker compose do? — easy
Kubernetes
- What is a Pod? — easy
- Deployment vs StatefulSet? — easy
- Explain the Service types. — medium
- A pod is in CrashLoopBackOff. How do you debug it? — medium
- Liveness vs readiness probes? — medium
- ConfigMap vs Secret? — medium
- What happens when you run kubectl apply -f deploy.yaml? — hard
- Requests vs limits? — medium
- Why is a pod stuck in Pending? — medium
- How do you roll back a Deployment? — easy
AWS
- What is the difference between a Region and an Availability Zone? — easy
- Security group vs network ACL? — easy
- IAM role vs IAM user? — medium
- Name the S3 storage classes and when to use them. — medium
- Public vs private subnet? — medium
- What is Auto Scaling and how does it work with a load balancer? — medium
- What is the shared responsibility model? — easy
- ALB vs NLB? — medium
- How do you make an RDS database highly available? — hard
- What is the difference between EBS and instance store? — easy
Networking / CCNA
- What are the layers of the OSI model? — easy
- TCP vs UDP? — easy
- How many usable hosts are in a /26 network? — medium
- What is a VLAN and what is a trunk? — medium
- Why do we need Spanning Tree Protocol? — medium
- Explain the administrative distance of common routing sources. — medium
- What is the difference between static NAT, dynamic NAT and PAT? — medium
- What does ARP do? — easy
- How does OSPF elect a DR on a broadcast segment? — hard
- What is the purpose of DHCP and its message sequence? — easy
Cyber security
- What is the CIA triad? — easy
- Symmetric vs asymmetric encryption? — easy
- What is SQL injection and how do you prevent it? — medium
- XSS vs CSRF? — medium
- Hashing vs encryption? — easy
- What is the difference between a vulnerability assessment and a penetration test? — medium
- What are the phases of incident response? — medium
- What is the principle of least privilege? — medium
- How does a TLS handshake work (TLS 1.3)? — hard
- What is phishing and how do organisations reduce it? — easy