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

1. Check permissions: id, ls -la
2. Check disk: df -h, du -sh /*
3. Check memory: free -h
4. Check logs: journalctl -xe

Recovery Procedures

Out of Disk Space

1. Find large files: du -sh /* | sort -rh | head
2. Clean cache: apt clean
3. Rotate logs: journalctl --vacuum-size=100M

Resources

• Linux Journey
• TLDR Pages