LSS_JC - Linux Shell Scripting (Project-Based)

My practice repo for the Udemy course Linux Shell Scripting: A Project-Based Approach to Learning. In the course you learn Bash by building six sysadmin tools on CentOS 7 VMs managed with Vagrant + VirtualBox. Each lesson is logged as a GitHub issue.

Projects

#	Script	What it does
1	add-local-user.sh	Prompts for a username, name and password, then creates the account and forces a password change at first login
2	add-new-local-user.sh	Takes the username and comment as arguments and generates a random password
3	add-newer-local-user.sh	Same as #2, but follows Unix conventions: errors go to STDERR, command noise goes to /dev/null
4	disable-local-user.sh	Disables, deletes (-d) or archives (-a) accounts, optionally removing home directories (-r). Skips system accounts
5	show-attackers.sh	Prints a CSV of IPs with more than 10 failed SSH logins, with each IP's country
6	run-everywhere.sh	Runs one command on many servers over SSH. Options: dry run -n, sudo -s, verbose -v, server list -f

Requirements

• VirtualBox, Vagrant and Git
• VT-x/AMD-V enabled in BIOS
• Windows only: disable Hyper-V, and run git config --global core.autocrlf input before cloning so scripts keep LF line endings

Setup

git clone https://github.com/dev000000/Linux-Shell-Scripting-Jason_Cannon.git
cd Linux-Shell-Scripting-Jason_Cannon
vagrant box add jasonc/centos7

Projects 1–5 run on a single VM:

cd localusers && vagrant up && vagrant ssh
cd /vagrant            # the host's localusers/ folder, shared into the VM

Project 6 runs on three VMs: admin01 (192.168.56.10), server01 (.11) and server02 (.12):

cd multinet && vagrant up && vagrant ssh admin01
# on admin01, one-time setup:
echo "192.168.56.11 server01" | sudo tee -a /etc/hosts
echo "192.168.56.12 server02" | sudo tee -a /etc/hosts
ssh-keygen                                   # press Enter at every prompt
ssh-copy-id server01 && ssh-copy-id server02 # password: vagrant
cd /vagrant

Project structure

.
├── documents/        # Course handouts for Exercises 1–7 (PDF)
├── testbox01/        # Exercise 1: first test VM
├── multitest/        # Exercise 1: two-VM test
├── localusers/       # Projects 1–5
│   ├── Vagrantfile
│   ├── demos/        # luser-demo01–14.sh: scripts from the course videos + access_log sample
│   ├── exercises/    # Exercise 2–6 solutions + syslog-sample
│   └── lessons/      # 01–10: my study notes written as scripts
├── multinet/         # Project 6
│   ├── Vagrantfile   # admin01, server01, server02
│   ├── demos/        # multinet-demo01.sh (ping check) + servers list
│   ├── exercises/    # run-everywhere.sh
│   └── lessons/      # 11: SSH and remote-command notes
└── .claude/skills/study-log/   # Claude Code skill: one issue + one commit per lesson

• demos/: scripts from the course videos, with my notes added
• exercises/: my solutions to the PDF exercises
• lessons/: reference notes. Copy commands one by one instead of running the file; some lines delete users or files

Usage

Scripts are not executable in git. Inside the VM, run them with bash (add sudo when needed):

sudo bash exercises/add-new-local-user.sh dstamper Doug Stamper
sudo bash exercises/disable-local-user.sh -dra dstamper
bash exercises/show-attackers.sh exercises/syslog-sample
bash exercises/run-everywhere.sh -v -s id        # on admin01, as vagrant (not root)

Learning log

• One issue per lesson. The title is N.<topic>; the body holds the course lesson title, an (S<section>-L<lecture>) tag and the key points.
• Commits follow Conventional Commits (lesson(scope): …, fix, refactor, chore, docs) and end with Refs: #N.

Notes

• Run scripts only inside the VMs: they create, lock and delete users.
• If vagrant up rejects the 10.9.8.x IPs in testbox01/ or multitest/, add * 10.0.0.0/8 192.168.0.0/16 to /etc/vbox/networks.conf on the host.
• CentOS 7 is end-of-life, so yum install needs the repos switched to vault.centos.org.

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Course and exercise handouts © Jason Cannon / Linux Training Academy. Solutions and notes by @dev000000.