Linux Administration

If you're diving into DevOps, understanding Linux system administration is crucial! Here’s a beginner-friendly breakdown of key concepts, covering user management, permissions, log analysis, disk usage, process monitoring, and automation.

🔹 1️⃣ User & Group Management

Linux users and groups help organize access control.

Every user is stored in /etc/passwd, and group details are in /etc/group.
You can create a user and add them to a group for better access management.
Grant sudo access to allow administrative privileges.
Restrict SSH logins for security in /etc/ssh/sshd_config.

💡 Example:
To create a user devops_user and add them to devops_team:

sudo useradd -m devops_user sudo groupadd devops_team sudo usermod -aG devops_team devops_user sudo passwd devops_user # Set a password

sudo useradd -m devops_user  
sudo groupadd devops_team  
sudo usermod -aG devops_team devops_user  
sudo passwd devops_user  # Set a password

📁 2️⃣ File & Directory Permissions

File permissions define who can read, write, or execute files in Linux.

The ls -l command shows file permissions.
Use chmod to modify them.
A secure directory structure ensures controlled access to files.

💡 Example:
To create a workspace directory and restrict access:

mkdir /devops_workspace  
touch /devops_workspace/project_notes.txt  
chmod 740 /devops_workspace/project_notes.txt  # Owner can edit, group can read, others denied

📝 3️⃣ Log File Analysis with AWK, Grep & Sed

Logs help monitor system activity. Using Linux tools, we can analyze them efficiently.

grep finds specific error messages in log files.
awk extracts useful data like timestamps and log levels.
sed replaces sensitive details for security.

💡 Example:
To filter logs containing errors and hide IP addresses:

grep "error" Linux_2k.log  
awk '{print $1, $2, $3}' Linux_2k.log  # Extract timestamp and log level  
sed 's/[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}/[REDACTED]/g' Linux_2k.log

💾 4️⃣ Volume Management & Disk Usage

Efficient storage management prevents performance bottlenecks.

Mount new storage volumes for expanding data capacity.
Use df -h to check disk space usage.
Verify mounts with mount | grep devops_data.

💡 Example:
To create and mount a new directory:

mkdir /mnt/devops_data  
mount /dev/sdb1 /mnt/devops_data  # Mount a new volume  
df -h | grep devops_data  # Verify disk space

🔍 5️⃣ Process Management & Monitoring

Processes keep systems running, but monitoring them prevents overload.

Use ps, top, and htop to monitor system performance.
Stop unwanted processes with kill.

💡 Example:
To start a background process and monitor it:

ping google.com > ping_test.log &  
ps aux | grep ping  
top  # Real-time monitoring  
kill $(pgrep ping)  # Stop the process

🔄 6️⃣ Automate Backups with Shell Scripting

Automate backups to protect important data!

💡 Example:
A simple script to create daily backups:

#!/bin/bash  
tar -czf /backups/backup_$(date +%F).tar.gz /devops_workspace  
echo -e "\e[32mBackup successful!\e[0m"

Save this script in /backups and schedule it with cron for automatic execution!

🚀 DevOps Essentials: Mastering Linux Administration