🧠 Mastering Linux Administration: A Step-by-Step Hands-on Lab Guide

🔐 1. User & Group Management

🔎 What are Linux users, groups, and permissions?

Users:

• Linux is a multi-user OS.

• User types:

  • Root User: Full system access.

  • System Users: Services and daemons.

  • Regular Users: Human users.

Groups:

• A group gives a set of users shared permissions.

• Example: developers can modify code, marketing can only read docs.

Permissions Example:

-rw-r--r-- 1 user1 user1 48 Feb 5 10:00 file.txt

• rw- Owner: Read + Write

• r-- Group: Read

• r-- Others: Read

Modify Permissions:

chmod 764 file.txt

• 7 = Owner (rwx), 6 = Group (rw-), 4 = Others (r--)

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🧪 Task 1: Create user and group

sudo useradd -m devops_user -s /bin/bash
sudo groupadd devops_team
sudo gpasswd -M devops_user devops_team
cat /etc/group

🧪 Task 2: Set password and give sudo access

sudo passwd devops_user
sudo usermod -aG sudo devops_user
cat /etc/group

🧪 Task 3: Restrict SSH login

Edit file:

sudo vim /etc/ssh/sshd_config

Add:

DenyUsers user1 user2
DenyGroup devops_team

Restart SSH:

sudo systemctl restart sshd

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📁 2. File & Directory Permissions

🧪 Task 1: Create directory and file

sudo mkdir devops_workspace
cd devops_workspace
sudo touch project_note.txt

🧪 Task 2: Set permissions

sudo chmod 740 project_note.txt
ls -l

• Owner: read/write

• Group: read

• Others: no access

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📄 3. Log File Analysis (AWK, GREP, SED)

🔍 grep: Find "authentication failure"

grep -i "authentication failure" app.log

🧮 awk: Extract timestamps and fields

awk '/authentication failure/ {print $1, $2, $3, $7}' app.log | head
awk '/authentication failure/ {print $1, $2, $3, $7}' app.log | tail

🛠 sed: Mask IPs

sed -E "s/([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+|[0-9a-fA-F:]+:[0-9a-fA-F:]+)/[REDACTED]/g" auth_fail_ips.txt

🔁 Unique entries

sed "s/rhost/IP/g" auth_fail_ips.txt | uniq

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💽 4. Volume Management & Disk Usage

🧪 Task 1: Setup volume and LVM

mkdir -p /mnt/devops_data

Volume Management complete video : https://www.youtube.com/watch?v=Evnf2AAt7FQ
Create volumes in AWS Console (same region/zone as EC2).Attach to instance as /dev/sdf.

Check block devices:

lsblk

Create physical volumes:

sudo su
pvcreate /dev/xvdf /dev/xvdg

Create volume group:

vgcreate tws_vg /dev/xvdf /dev/xvdg

Create logical volume:

vcreate -L 1.5G -n tws_lv tws_vg

🧪 Task 2: Format and mount

mkfs.ext4 /dev/tws_vg/tws_lv
mount /dev/tws_vg/tws_lv /mnt/devops_data/

🧪 Task 3: Verify volume

df -h | grep devops_data

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🖥 5. Process Management & Monitoring

🧪 Task 1: Start a background process

ping google.com > ping_test.log &

🧪 Task 2: Monitor process

ps aux | grep ping
top
htop   # Install with: sudo apt install htop

🧪 Task 3: Kill process

ps aux | grep ping
kill <PID>

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✅ Final Thoughts

Understanding Linux user/group management, permissions, log parsing, disk volumes, and process monitoring is essential for any DevOps or system admin professional. This hands-on guide helps build practical confidence to manage real-world Linux systems efficiently and securely.

Happy Learning! 🚀

#Linux #DevOps #System Administration #AWS #Volume Management #Monitoring