Appendix C: Glossary
Friends, if you forget a word, look here. Each term has a short definition – take a quick look before an interview.
मित्रांनो, एखादा शब्द विसरलात तर इथे बघा. प्रत्येक टर्मची छोटी व्याख्या दिली आहे – इंटरव्ह्यूआधी एकदा नजर फिरवा.
दोस्तों, कोई शब्द भूल जाओ तो यहाँ देखो. हर टर्म की छोटी परिभाषा दी गई है – इंटरव्यू से पहले एक बार नज़र डाल लो.
| Term | Meaning |
|---|---|
| A record | DNS record mapping a name to an IPv4 address |
| AMI | Amazon Machine Image — template (OS + software) to launch EC2 instances |
| Auto Scaling group (ASG) | Group of EC2 instances that AWS adds/removes automatically based on demand or health |
| AZ (Availability Zone) | One or more isolated data centres within an AWS Region |
| Block device mapping | Part of an AMI/launch that lists which volumes (root, data) attach to an instance, their device names, sizes and types |
| Bastion host | A hardened server used as the only SSH entry point into private subnets |
| CNAME | DNS alias record pointing one name to another name; not allowed at the apex |
| CIDR | Classless Inter-Domain Routing notation, e.g. 10.0.0.0/16 |
| cloud-init | Tool that configures an instance at first boot (runs user data, grows root partition) |
| Daemon | Background service process (e.g. sshd, nginx) |
| DLM (Data Lifecycle Manager) | AWS service that automates creation and deletion of EBS snapshots and EBS-backed AMIs |
| DHCP | Protocol that assigns IP addresses automatically |
| DNS | Domain Name System — translates names to IP addresses using a hierarchy of root, TLD and authoritative name servers |
| Document root / DocumentRoot | Folder from which a web server serves files (root in Nginx, DocumentRoot in Apache) |
| EBS | Elastic Block Store — persistent block storage volumes for EC2 |
| EC2 | Elastic Compute Cloud — AWS virtual servers |
| Elastic IP | Static public IPv4 address allocated to your AWS account |
| ELB (Elastic Load Balancer) | Managed load balancer (ALB/NLB) that spreads traffic across instances |
| ENI | Elastic Network Interface — virtual network card of an instance |
| FastCGI / PHP-FPM | Protocol / process manager that lets web servers run PHP efficiently |
| firewalld | Dynamic host firewall used on RHEL/CentOS |
| FQDN | Fully qualified domain name, e.g. blog.example.com. |
| fstab | /etc/fstab — file listing filesystems to mount at boot |
| Golden AMI | Standard, patched, pre-configured image from which all servers are launched |
| Gunicorn | Production WSGI HTTP server for Python web apps |
| Horizontal scaling | Adding/removing instances (scale out/in), usually with ASG + ELB |
| IAM | Identity and Access Management — users, groups, roles and policies in AWS |
| IGW | Internet Gateway — connects a VPC to the internet |
| IMDS | Instance Metadata Service at 169.254.169.254 (use IMDSv2 tokens) |
| IOPS | Input/output operations per second — storage performance measure |
| Key pair | Public/private key used for SSH authentication to EC2 |
| LTS | Long Term Support release (e.g. Ubuntu 24.04 LTS, Node.js LTS) |
| NAT | Network Address Translation — maps private IPs to a public IP |
| NAT Gateway | AWS managed service giving private subnets outbound internet access |
| Name server (NS) | Authoritative DNS server that answers queries for a domain; set at the registrar |
| NACL | Network Access Control List — stateless subnet-level firewall |
| Nitro | AWS hypervisor/hardware platform; EBS appears as NVMe devices |
| pm2 | Production process manager for Node.js applications |
| Port | 16-bit number identifying a service on a host (0–65535) |
| Registrar | Company that registers and renews domain names (GoDaddy, Namecheap, Route 53 Domains) |
| Region | Geographic area containing multiple AZs, e.g. ap-south-1 (Mumbai) |
| Reverse proxy | Server (Nginx/Apache) that forwards client requests to backend apps |
| Route 53 | AWS DNS service: hosted zones, records, Alias records, domain registration |
| RFC 1918 | Standard defining private IPv4 ranges 10/8, 172.16/12, 192.168/16 |
| Scale up (vertical scaling) | Moving to a bigger instance type (more vCPU/RAM); needs stop/start |
| Server block | Nginx server { } section defining one website (port, server_name, root) |
| Security group | Stateful virtual firewall attached to instances/ENIs |
| SELinux | Security-Enhanced Linux — mandatory access control on RHEL/CentOS |
| Service quota | Per-account, per-region limit on resources (e.g. 5 Elastic IPs by default) |
| Snapshot | Incremental point-in-time backup of an EBS volume |
| SPA | Single Page Application (React, Angular) |
| Subdomain | Name to the left of your domain, e.g. blog.example.com; created free with a DNS record |
| Subnet | A range of IP addresses within a VPC, located in one AZ |
| systemd | Linux init system and service manager (systemctl, journalctl) |
| TLD | Top-level domain such as .com, .in, .org |
| TLS/SSL | Encryption protocol used by HTTPS |
| TTL | Time To Live — seconds a DNS answer may be cached by resolvers |
| User data | Script passed to an instance that runs at first boot |
| UUID | Universally unique identifier of a filesystem, used in fstab |
| Virtual host | Apache <VirtualHost> section defining one website; name-based vhosts share one IP and port |
| VPC | Virtual Private Cloud — your isolated network in AWS |
| WSGI | Python standard interface between web servers and Python apps |
Practice Tasks
Nairobi Ride is a transport business in Nairobi. Wanjiru Kamau looks after its IT and cloud work. They count money in KES and run their AWS resources in the af-south-1 Region. In the tasks below you do real jobs for them using what this lesson teaches. All names, account IDs, IP addresses and numbers are made up for practice.
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Easy List your EC2 instances
Why: Before changing anything, see what is running and in which state.
What to do: Show details of all EC2 instances of Nairobi Ride in af-south-1.
- Read the task and decide which AWS service it is about.
- Write aws, then the service name, then the operation (the action word).
- Add each needed flag (--name) followed by its value from the task.
- Flags can be in any order. Click Check answer.
Easy List files in a bucket folder
Why: Check that the upload worked and see file sizes.
What to do: List the objects under s3://nairobiride-invoices-2026/reports/.
- Read the task and decide which AWS service it is about.
- Write aws, then the service name, then the operation (the action word).
- Add each needed flag (--name) followed by its value from the task.
- Flags can be in any order. Click Check answer.
Easy Create a bucket
Why: A bucket is the top-level container for your files in S3.
What to do: Create the bucket nairobiride-invoices-2026 in af-south-1.
- Read the task and decide which AWS service it is about.
- Write aws, then the service name, then the operation (the action word).
- Add each needed flag (--name) followed by its value from the task.
- Flags can be in any order. Click Check answer.
Easy How many addresses in a /16?
Why: Picking a VPC size needs this count.
What to do: Nairobi Ride plans the VPC 10.205.0.0/16. How many IP addresses does it hold in total?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Medium First usable IP for a server
Why: The first 4 addresses are reserved by AWS.
What to do: What is the first IP address a server can get in 10.205.20.0/24 on AWS?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Medium Do these VPCs overlap?
Why: Peering fails when ranges overlap.
What to do: Can VPC 10.205.0.0/16 peer with VPC 10.205.128.0/17? Answer yes or no.
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Medium Find the VPC router address
Why: AWS reserves base+1 for the router.
What to do: Which address does AWS reserve for the VPC router in subnet 10.205.4.0/24?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Medium Usable IPs in an AWS /24 subnet
Why: AWS keeps 5 addresses in every subnet.
What to do: How many addresses can Nairobi Ride use for servers in subnet 10.205.1.0/24 on AWS?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Medium Usable IPs in a /28
Why: /28 is the smallest AWS subnet.
What to do: Subnet 10.205.9.0/28 on AWS. How many usable IPs?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Hard Pick the smallest prefix
Why: Right-sizing saves address space.
What to do: A subnet must hold 100 servers on AWS. What is the largest prefix number (smallest subnet) that fits? Answer like /25.
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Hard Range of a /26
Why: Knowing the range stops subnets from overlapping.
What to do: Write the first and last address of 10.205.3.64/26 (like a.b.c.d - e.f.g.h).
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Hard Split a /24 into two
Why: Public and private subnets often split one block.
What to do: Split 10.205.8.0/24 into two equal subnets. Write both CIDRs separated by a comma.
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.