linux-handbook

---

✅ Project Structure

linux-server-automation-setup/
│
├── basic/
│   ├── create_group_users.sh
│   ├── set_permissions.sh
│   ├── install_packages.sh
│   └── system_info.sh
│
├── intermediate/
│   ├── automate_backup.sh
│   ├── log_cleanup.sh
│   ├── check_service_status.sh
│   └── performance_monitor.sh
│
└── advanced/
    ├── custom_systemd_service.sh
    ├── ssh_hardening.sh
    ├── lvm_setup.sh
    ├── firewall_setup.sh
    └── logrotate_config.sh

---

---

🟩 Folder: basic

basic

1️⃣ create_users.sh

#!/bin/bash
sudo groupadd devteam
for user in dev1 dev2 dev3; do
    sudo useradd -m -G devteam $user
    echo "User $user created and added to devteam"
done

2️⃣ set_permissions.sh

#!/bin/bash
sudo mkdir -p /opt/devproject
sudo chown :devteam /opt/devproject
sudo chmod 770 /opt/devproject
echo "Permissions set for /opt/devproject"

3️⃣ install_packages.sh

#!/bin/bash
sudo yum update -y
sudo yum install -y git nginx java-17-amazon-corretto
sudo systemctl enable nginx
sudo systemctl start nginx
echo "Git, Nginx & Java installed successfully on Amazon Linux"

4️⃣ system_info.sh

#!/bin/bash
echo "CPU Info:"; lscpu
echo "Memory Info:"; free -h
echo "Disk Info:"; df -h

---

🟨 Folder: intermediate

intermediate

1️⃣ automate_backup.sh

#!/bin/bash
SOURCE=/opt/devproject
BACKUP=/backup/devproject_$(date +%F).tar.gz
sudo tar -czvf $BACKUP $SOURCE
echo "Backup stored at $BACKUP"

(Add to cron: 0 2 * * * /path/automate_backup.sh)

2️⃣ log_cleanup.sh

#!/bin/bash
find /var/log -type f -mtime +7 -exec rm -f {} \;
echo "Old logs cleared"

3️⃣ check_service_status.sh

#!/bin/bash
SERVICES="nginx ssh"
for svc in $SERVICES; do
    sudo systemctl is-active --quiet $svc && \
    echo "$svc is running" || \
    echo "$svc is down"
done

4️⃣ performance_monitor.sh

#!/bin/bash
echo "---CPU Load---"; top -b -n1 | head -5
echo "---Disk Space---"; df -h
echo "---Memory---"; free -h

---

🟥 Folder: advanced

advanced

1️⃣ custom_systemd_service.sh

#!/bin/bash
cat <<EOF | sudo tee /etc/systemd/system/myapp.service
[Unit]
Description=My Custom App Service

[Service]
ExecStart=/usr/bin/python3 /opt/myapp/app.py
Restart=always

[Install]
WantedBy=multi-user.target
EOF

sudo systemctl daemon-reload
sudo systemctl enable myapp
sudo systemctl start myapp

2️⃣ ssh_hardening.sh

#!/bin/bash
sudo sed -i 's/#PasswordAuthentication yes/PasswordAuthentication no/' /etc/ssh/sshd_config
sudo systemctl restart sshd
echo "SSH Hardening Applied: Password login disabled"

3️⃣ lvm_setup.sh

#!/bin/bash
sudo pvcreate /dev/sdb
sudo vgcreate myvg /dev/sdb
sudo lvcreate -n mylv -L 5G myvg
sudo mkfs.ext4 /dev/myvg/mylv
sudo mkdir /mnt/lvmdata
sudo mount /dev/myvg/mylv /mnt/lvmdata
echo "LVM setup completed"

4️⃣ firewall_setup.sh

#!/bin/bash
sudo ufw allow OpenSSH
sudo ufw allow 80/tcp
sudo ufw allow 443/tcp
sudo ufw logging on
echo "Enabling UFW firewall..."
sudo ufw --force enable

echo "Firewall configured: SSH, HTTP, HTTPS allowed"
sudo ufw status verbose

5️⃣ logrotate_config.sh

#!/bin/bash
cat <<EOF | sudo tee /etc/logrotate.d/myapp
/var/log/myapp.log {
    daily
    rotate 7
    compress
    missingok
    notifempty
}
EOF
echo "Logrotate config added"

---

👉 Execution Steps

chmod +x basic/*.sh
chmod +x intermediate/*.sh
chmod +x advanced/*.sh

Now run any script, e.g.:

./basic/install_packages.sh

---

🚀 GitHub Upload Instructions

git init
git add .
git commit -m "Initial automation project commit"
git branch -M main
git remote add origin <your_github_repo_url>
git push -u origin main

---

What is Linux?

Linux is an open-source operating system based on the Unix architecture. It acts as a bridge between hardware and applications, managing processes, memory, file systems, and security.

💡 Key points:

• Open-source → source code is freely available
• Highly secure and stable
• Most servers, cloud platforms, and DevOps environments run on Linux
• Supports CLI (Command Line Interface) and GUI

Commonly used in:

• AWS, Azure, GCP servers
• Containers (Docker uses Linux kernel features)
• CI/CD tools, Kubernetes, DevOps automation

---

Dynamic Linux Commands for DevOps Engineers

Here are the most important commands grouped by usage:

---

🔍 System & Process Monitoring

Command	Purpose
top / htop	View running processes live
ps aux	Detailed process list
free -h	Memory usage
df -h	Disk space usage
du -sh *	Disk usage by files/folders
systemctl status <service>	Check service status
journalctl -xe	View logs for system services

---

📂 File & Directory Management

Command	Purpose
ls -l	Detailed directory view
cd, pwd	Navigate paths
mkdir, rmdir	Create/remove folders
cp, mv, rm -rf	Copy/move/delete
find / -name filename	Search files
touch, cat, less, head, tail -f	Create & view files

---

🔐 Permissions & Ownership

Command	Purpose
chmod 755 file	Change permissions
chown user:group file	Change ownership
useradd, passwd, usermod	User management

---

🌐 Network Commands

Command	Purpose
ifconfig / ip a	Check network interfaces
ping google.com	Check connectivity
curl <URL>	API testing
netstat -tulnp or ss -tulnp	Check open ports
scp, rsync	Transfer files between servers

---

📝 Log & File Inspection

Command	Purpose
grep "error" filename	Search inside files
awk, sed	Text processing (mostly used in automation)
tail -f /var/log/messages	Live log view

---

🔧 Package Management

OS Type	Commands
RHEL/CentOS	yum install, rpm -qa
Ubuntu/Debian	apt-get install, dpkg -l

---

🐳 Container & DevOps Tools (Bonus)

Tool	Example Command
Docker	docker ps, docker images
Git	git status, git pull, git log
Kubernetes	kubectl get pods

---

💡 Tip for Interviews

They often ask:

• How do you check CPU/memory usage?
• How do you find which process is using a port?
• How do you monitor logs in real time?
• How do you troubleshoot service failure?