Linux Fundamentals Skill

Overview

Master Linux system administration - the foundation of DevOps.

Parameters

Name Type Required Default Description

distro string No ubuntu Target distribution

operation string Yes

Operation category

Core Topics

MANDATORY

• Process lifecycle and management (ps, top, kill)

• Filesystem hierarchy and operations

• File permissions (chmod, chown, ACLs)

• Package management (apt, yum, dnf)

• User and group administration

• Basic bash scripting

OPTIONAL

• LVM and disk partitioning

• Systemd service management

• Log analysis with journalctl

ADVANCED

• Kernel parameters and sysctl

• SELinux/AppArmor security

• Performance profiling

Quick Reference

Process Management

ps aux | grep [p]rocess # Find process (avoid grep itself) kill -15 PID # Graceful termination kill -9 PID # Force kill (last resort) pkill -f pattern # Kill by pattern nohup command & # Background immune to hangup

File Permissions

chmod 755 file # rwxr-xr-x chmod u+x,g+r file # Symbolic notation chown -R user:group dir/ # Recursive ownership setfacl -m u:user:rw file # Set ACL

Package Management (Debian/Ubuntu)

apt update && apt upgrade -y apt install -y package apt autoremove

Package Management (RHEL/CentOS)

dnf update -y dnf install package

User Management

useradd -m -s /bin/bash user usermod -aG sudo user passwd user

System Info

uname -a # Kernel info cat /etc/os-release # OS version free -h # Memory usage df -h # Disk usage

Troubleshooting

Common Failures

Symptom Root Cause Solution

Permission denied Insufficient privileges Use sudo or check ownership

Command not found Package not installed Install with apt/dnf

No space left Disk full Clean /var/log, docker prune

High load CPU/IO bottleneck Use top, iotop

Debug Checklist

• Check permissions: id , ls -la

• Check disk: df -h , du -sh /*

• Check memory: free -h

• Check logs: journalctl -xe

Recovery Procedures

Out of Disk Space

• Find large files: du -sh /* | sort -rh | head

• Clean cache: apt clean

• Rotate logs: journalctl --vacuum-size=100M

Resources

• Linux Journey

• TLDR Pages