Master Linux & AWS fundamentals.
A practical reference for Linux commands, AWS infrastructure, storage, networking, scalability and common DevOps concepts.
Linux Essentials
Commands you should know for everyday server administration.
Files & Directories
Navigate, create, copy, move and remove files.
pwd ls -la cd /var/log mkdir app touch file.txt cp file.txt /tmp/ mv old.txt new.txt rm file.txt
Files & Text
Read and search through configuration and log files.
cat config.txt less application.log head file.txt tail -f app.log grep "ERROR" app.log find /var -name "*.log"
System & Processes
Monitor CPU, memory, disk usage and running processes.
ps aux top df -h du -sh folder/ free -h uptime kill PID
Linux permissions commonly use read (r), write (w) and execute (x). For example, 755 means the owner has full permissions while group and others can read and execute.
Amazon EC2
Elastic Compute Cloud — virtual servers in AWS.
What is EC2?
EC2 provides resizable compute capacity. Think of an EC2 instance as a virtual machine running inside AWS.
AMI
An Amazon Machine Image is a template used to launch EC2 instances. It can contain an operating system and preconfigured software.
Security Group
A virtual firewall that controls inbound and outbound traffic for supported AWS resources.
ssh -i my-key.pem ec2-user@<public-ip> # Ubuntu ssh -i my-key.pem ubuntu@<public-ip>
Elastic IP
A persistent public IPv4 address.
An Elastic IP is a static public IPv4 address that can be associated with an AWS resource such as an EC2 instance. It can be remapped when needed.
Amazon EBS
Elastic Block Store — persistent block storage for EC2.
Virtual Hard Disk
EBS volumes behave like virtual disks that can be attached to EC2 instances.
Persistent
EBS is designed for persistent data such as operating systems, applications and databases.
Snapshots
EBS volumes can be backed up using snapshots, which are stored in AWS-managed storage.
Amazon S3
Simple Storage Service — scalable object storage.
Objects
S3 stores data as objects inside buckets. Objects can contain files, metadata and associated information.
Common Uses
Backups, images, videos, logs, static websites, application assets and data lakes.
Versioning
S3 versioning can retain multiple versions of objects and help protect against accidental deletion or overwrites.
aws s3 ls aws s3 cp file.txt s3://my-bucket/ aws s3 cp s3://my-bucket/file.txt .
Block vs Object Storage
The difference you should remember for interviews.
| Feature | Block Storage | Object Storage |
|---|---|---|
| AWS Example | EBS | S3 |
| Data Model | Blocks | Objects |
| Access | Disk / filesystem | API / HTTP |
| Typical Use | OS, applications, databases | Images, backups, logs, media |
| Scaling | Volume based | Highly scalable |
| Simple Example | /data/database | s3://bucket/image.jpg |
EBS = hard disk for your EC2. | S3 = storage bucket for your objects.
Elastic Load Balancing
Distribute incoming traffic across healthy targets.
Application Load Balancer
Designed primarily for HTTP and HTTPS applications with advanced application-layer routing.
Network Load Balancer
Designed for high-performance TCP, UDP and TLS workloads.
Health Checks
Load balancers can check target health and route traffic to healthy targets.
Auto Scaling
Automatically adjust compute capacity based on demand.
Scale Out
When demand increases, additional EC2 instances can be launched.
Scale In
When demand decreases, instances can be terminated according to the configured policy.
Self Healing
Auto Scaling can replace unhealthy instances to maintain the desired capacity.
Amazon VPC
Your logical network inside AWS.
VPC
Logical network environment for AWS resources.
Subnet
A subdivision of a VPC IP address range.
Route Table
Controls where network traffic is directed.
Security Groups
Control network access to supported AWS resources.
PORT PROTOCOL PURPOSE 22 TCP SSH 80 TCP HTTP 443 TCP HTTPS
Follow least privilege. Only expose the ports and sources that your application actually needs.
Amazon RDS
Managed relational databases in AWS.
Managed Database
AWS manages many infrastructure and operational tasks, reducing database administration overhead.
Engines
Common options include PostgreSQL, MySQL, MariaDB, Oracle, SQL Server and Aurora.
Backups
RDS provides managed backup capabilities and other features designed to simplify database operations.
Amazon CloudWatch
Monitor resources, applications, metrics and logs.
Metrics
Collect and visualize resource and application metrics.
Logs
Centralize and inspect logs from applications and AWS resources.
Alarms
Trigger actions when configured metric thresholds are reached.
Typical AWS Architecture
How common AWS services can work together.
Interview Questions
Quick questions to test your fundamentals.