How To: Linux File System Hierarchy and Command Guide for SRE & AIOps

Introduction

In Site Reliability Engineering (SRE) and AIOps, mastery of the Linux file system and command-line utilities is crucial for effective system management, rapid troubleshooting, and operational automation, particularly in cloud-native and containerized environments.

Linux File System Hierarchy

Understanding the Structure

A clear grasp of the Linux file hierarchy enables efficient incident response, effective automation, and reliable system configurations, significantly reducing operational overhead and improving system resilience in SRE and AIOps contexts.

A strong understanding of the Linux file hierarchy enables faster incident response, efficient automation, and reliable system configuration, which are essential in SRE and AIOps.

Directory	Purpose & Typical Usage
/	Root directory, top-level of the hierarchy.
/bin	Essential user binaries (e.g., ls, cp, mv).
/boot	Boot loader files and kernels.
/dev	Device files (e.g., /dev/sda).
/etc	System-wide configuration files (e.g., /etc/nginx/nginx.conf).
/home	User home directories.
/lib	Essential shared libraries required for binaries in /bin and /sbin.
/mnt	Temporary mount point for manually mounted file systems.
/opt	Add-on software applications, often used for third-party tools like Prometheus, Grafana, or custom scripts.
/proc	Virtual file system providing process and kernel information, such as /proc/cpuinfo, /proc/meminfo, crucial for performance monitoring.
/root	Home directory for the root user.
/sbin	Essential system binaries (e.g., fdisk, iptables).
/srv	Data for services provided by the system (e.g., websites, FTP data).
/sys	Information about kernel and system hardware.
/tmp	Temporary files.
/usr	Secondary hierarchy with read-only user data; contains binaries, libraries, documentation, and source code.
/var	Variable data like logs (/var/log/messages, /var/log/kern.log), databases (/var/lib), and runtime data (/var/run).

Essential Linux Commands for SRE and AIOps

Proficiency and efficiency with Linux command-line tools are critical in operational scenarios, enabling SRE and AIOps teams to quickly diagnose issues, automate repetitive tasks, and maintain robust system reliability.

Efficient use of command-line tools is integral to operational effectiveness and rapid troubleshooting.

System Monitoring & Performance

These commands help monitor system health, analyze performance issues, and maintain optimal resource usage, crucial for maintaining service reliability.

Command	Description	Example
top	Real-time system monitoring; consider alternatives like glances, nmon.	top
htop	Enhanced interactive version of top	htop
vmstat	Virtual memory statistics	vmstat 2 5
iostat	I/O statistics for devices and partitions	iostat -x 1
free	Memory usage statistics	free -m
sar	Collect and report performance metrics	sar -u 1 3
mpstat	CPU statistics	mpstat -P ALL

Log Analysis

Effective log analysis enables rapid identification of issues, debugging, and informed decision-making, improving overall system resilience and uptime.

Command	Description	Example
tail	Latest lines of files	tail -f /var/log/syslog
grep	Search text patterns in files	grep ERROR /var/log/syslog
journalctl	Query systemd logs, filter by time-range or priority	journalctl -u nginx.service --since today
awk, sed	Advanced log parsing	awk '/error/ {print $0}' /var/log/syslog

Process Management

Managing processes efficiently is essential for ensuring service continuity, quickly resolving issues, and optimizing system performance.

Command	Description	Example
ps	Report process status	ps aux | grep nginx
kill	Terminate processes	kill -9 <PID>
systemctl	Manage systemd services	systemctl restart nginx.service
nice, renice	Manage process priority	renice -n 10 -p <PID>

Network and Security

Maintaining a secure and stable network environment is critical for SRE and AIOps teams, preventing downtime and ensuring robust security measures.

Command	Description	Example
netstat	Network connections, routing tables, interface stats	netstat -tulnp
ss	Investigate sockets and connections	ss -ltn
iptables, firewalld	Firewall configuration	iptables -L
nmap	Network exploration	nmap -sT -p 80,443 server.example.com
tcpdump	Packet capture	tcpdump port 443

Files and Permissions

Properly managing file permissions and efficiently locating files are key aspects of operational security and efficient troubleshooting.

Command	Description	Example
chmod	Modify file permissions; important for security	chmod 755 script.sh
chown	Change file ownership	chown root:admin /var/www
ls	List directory contents	ls -l /var/log
find, locate	Find files quickly	find /var/log -name '*.log'

Disk and Storage

Disk and storage management commands assist in effectively monitoring storage usage, preventing critical failures, and optimizing performance.

Command	Description	Example
df	Disk space usage	df -h
du	Estimate file/directory space usage	du -sh /var/log
mount	Mount file systems	mount /dev/sdb1 /mnt/backup
lvm	Logical Volume Management	lvdisplay, vgextend

Package and Application Management

Efficient package and application management simplifies software installation, updates, and maintenance, promoting stability and consistency across environments.

Command	Description	Example
apt, yum, dnf	Package management tools	apt install nginx
docker	Container management	docker ps, docker logs <container>
kubectl	Kubernetes management, troubleshooting (describe, logs)	kubectl describe pod
helm	Kubernetes package manager, automation in deployments	helm install prometheus prometheus-community/prometheus
ansible, puppet	Configuration management	ansible-playbook setup.yml

Integrating Linux Commands with AIOps

Leveraging Linux commands within AIOps frameworks significantly reduces manual toil by automating routine tasks such as system monitoring, log analysis, incident detection, and remediation. Real-world examples include automatic disk space alerts, automated log rotation, proactive health checks, and self-healing services triggered through platforms like PagerDuty, Robusto, Jenkins, and GitLab CI/CD. These integrations enable SREs to shift focus toward high-value tasks and continuous improvement, ensuring systems remain reliable and performant.

Real-world integration of Linux commands with monitoring tools and CI/CD platforms significantly reduces manual toil and enhances reliability.

Example Automation Scenario (Enhanced):

#!/bin/bash
threshold=80
usage=$(df / | awk 'NR==2 {print $5}' | sed 's/%//')

if [ "$usage" -gt "$threshold" ]; then
  echo "Disk usage at $usage%" | mail -s "Disk Usage Alert" [email protected]
fi

Command Integration with Tools

• Monitoring Systems: Utilize vmstat, iostat, free in platforms like Prometheus/Grafana.
• Incident Management: Automate log retrieval (journalctl) and service remediation (systemctl) through orchestration tools like PagerDuty, Robusto, Jenkins, GitLab CI/CD.

Conclusion

Mastering Linux file systems and command-line utilities significantly enhances system reliability, reduces downtime, and accelerates incident response. Leveraging these tools in automation and integration with CI/CD pipelines empowers SRE and AIOps professionals to maintain resilient and efficient systems.