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
