Cloud Girl Logs — Week 1: AWS + Linux Foundations

This is week 1 of my Cloud + Linux learning log. I'm preparing for RHCSA and AWS SAA simultaneously — alternate days, one topic per session. Writing it down here so it sticks, and maybe it helps someone else starting out.

AWS Side

IAM — Identity and Access Management

IAM is how AWS controls who can do what inside your account. Every action — launching an EC2, reading S3, creating a user — goes through IAM first.

Things that actually clicked this week:

• Never use the root account for daily work. Create an IAM admin user and use that instead. Root is only for billing and account-level stuff

• Attach policies to groups, not individual users. Much easier to manage when you scale

• Least privilege — give only the permissions actually needed, nothing extra

• Explicit deny always wins. If one policy allows S3 access and another explicitly denies it, the deny wins every time. No exceptions

EC2 — Elastic Compute Cloud

EC2 is basically a virtual machine running in AWS. You pick the OS, instance type, storage, and networking — it's running in minutes.

What I focused on:

• Instance types — t2.micro is free tier, but there are different families optimized for compute, memory, or storage depending on the workload

• Key pairs — SSH access to your instance. You get one chance to download the private key when creating it. Lose it and you're locked out

• Security groups — act as a virtual firewall. Control what traffic can come in and go out of your instance

• Stopping vs terminating — stopping is like shutting down a PC, terminating deletes the instance completely

Linux Side

What even is Linux

Linux is an open source operating system kernel. The distributions (Ubuntu, RHEL, CentOS, Fedora) are built on top of it. For RHCSA specifically, everything is RHEL-based.

Firmware and Low-Level Software

Before the OS even loads, firmware (BIOS or UEFI) runs first. It initializes hardware and hands control to the bootloader, which then loads Linux. Not something you touch daily but important to understand the boot chain.

Run-levels and Targets

Older Linux used run-levels. Modern Linux uses systemd targets:

• multi-user.target — command line, no GUI (what servers use)

• graphical.target — desktop environment

• rescue.target — minimal mode for recovery

bash

systemctl get-default    # check current target

Linux File System Structure

Everything in Linux starts from / (root). Key directories worth knowing:

• /etc — configuration files

• /var — logs and variable data

• /home — user home directories

• /bin and /usr/bin — essential commands

• /tmp — temporary files, cleared on reboot

• /root — home directory for the root user specifically

SSH Setup

SSH lets you securely connect to a remote Linux machine:

bash

ssh -i keyfile.pem username@ip-address

For RHCSA, /etc/ssh/sshd_config controls server behavior — changing default port, disabling root login, key-based vs password auth are all exam-relevant.

DOS vs Linux Terminal

Working with Directories

bash

pwd             # where am I
ls -la          # list all including hidden files
mkdir name      # create directory
mkdir -p a/b/c  # create nested directories in one go
rm -rf name     # remove directory and everything in it

File Creation and Manipulation

bash

touch filename    # create empty file
cp file1 file2    # copy
mv file1 file2    # move or rename
rm filename       # delete

File Content Manipulation

bash

cat file          # print file content
head -n 5 file    # first 5 lines
tail -n 5 file    # last 5 lines
grep "word" file  # search for word inside file

grep is something you'll use constantly. Worth spending extra time on it.

Getting Help and Man Pages

bash

man ls       # full manual
ls --help    # quick summary
whatis ls    # one line description

Man pages are allowed in the RHCSA exam. Get comfortable using them now.

Inodes, Hard Links and Soft Links

An inode stores file metadata — permissions, owner, size, timestamps. Every file has one.

A hard link points to the same inode. Delete the original — the hard link still works.

A soft link (symlink) points to the filename. Delete the original — the symlink breaks.

bash

ln file hardlink       # hard link
ln -s file softlink    # soft link
ls -li                 # see inode numbers

What's next?
That’s a wrap on Week 1!
Next week, I’ll be diving into:
AWS: VPC, Security Groups, NACLs, IP Addressing
Linux: Shell Expansion(Shell Embedding, File Globbing, etc)

Full notes on GitHub: https://github.com/anousheh-hussain/cloud-devops-notes