RHCSA Cheat Sheet

RHEL Lightspeed Command-line Assistant

Purpose (Exam Context)

• AI‑assisted helper for RHEL administration
• Available in RHEL 9.6+ and RHEL 10
• Helps explain commands, logs, and outputs
• NOT required knowledge for RHCSA
• Exam environments are offline → do not rely on it

✅ Treat Lightspeed as built‑in documentation, not a replacement for core Linux skills.

Requirements

• Active RHEL subscription
• Internet connectivity
• Installed package: command-line-assistant

Installation

dnf install command-line-assistant

dnf install command-line-assistant

• Installs the c command
• Must be run as root

Core Command

Ask a Question

c chat "question in plain English"

c chat "question in plain English"

Example:

c chat "How do I list running services?"

c chat "How do I list running services?"

Interactive Mode

Used for multi‑step troubleshooting.

c chat --interactive

c chat --interactive

Exit:

• Ctrl + C
• or .exit

Service Management (RHCSA MUST‑KNOW)

List Running Services

systemctl list-units --type=service --state=running

systemctl list-units --type=service --state=running

Check Service Status

systemctl status sshd.service

systemctl status gdm.service

systemctl status sshd.service

systemctl status gdm.service

Lightspeed Example:

c chat "How do I check the status of the sshd service?"

c chat "How do I check the status of the sshd service?"

Log Analysis (HIGH IMPORTANCE)

View Logs for a Service

journalctl -u httpd.service --since "1 hour ago"

journalctl -u httpd.service --since "1 hour ago"

Analyze Logs with Lightspeed

journalctl -u httpd.service --since "1 hour ago" | c chat "What could be causing errors?"

journalctl -u httpd.service --since "1 hour ago" | c chat "What could be causing errors?"

Process & Memory Analysis

View Top Memory Consumers

ps aux --sort=-%mem

ps aux --sort=-%mem

Limit Output

ps aux --sort=-%mem | head -n 20

ps aux --sort=-%mem | head -n 20

Analyze with Lightspeed

ps aux --sort=-%mem | head -n 20 | c chat "Is there a memory leak?"

ps aux --sort=-%mem | head -n 20 | c chat "Is there a memory leak?"

File & Log File Analysis

View System Logs

cat /var/log/messages

cat /var/log/messages

Analyze Log Content

cat /var/log/messages | c chat "Look for critical errors"

cat /var/log/messages | c chat "Look for critical errors"

Attach Files Directly

Analyze Boot Log

c chat -a /var/log/boot.log "Why did the last boot take so long?"

c chat -a /var/log/boot.log "Why did the last boot take so long?"

Options:

• -a → attach file

Pipes (Exam Essential)

command | command | command

command | command | command

Examples you must know:

ps aux | head

journalctl -u sshd | less

cat /var/log/messages | grep error

ps aux | head

journalctl -u sshd | less

cat /var/log/messages | grep error

Lightspeed just reads piped output — it does not access files on its own.

Important Limitations (Exam Trap)

❌ Lightspeed cannot:

• Read system RAM, CPU, disks directly
• Access files unless you provide them
• Work without internet access

✅ It suggests commands instead

RHCSA Exam Takeaways

You must know these commands without AI help:

dnf

systemctl

journalctl

ps

cat

head

piping (|)

log locations (/var/log/*)

dnf

systemctl

journalctl

ps

cat

head

piping (|)

log locations (/var/log/*)

You are not tested on:

c chat

c chat

• Lightspeed architecture
• AI behavior

Quick Command Review (Memorize)

dnf install command-line-assistant

c chat "question"

c chat --interactive

systemctl list-units --type=service --state=running

systemctl status sshd.service

journalctl -u httpd.service --since "1 hour ago"

ps aux --sort=-%mem

head -n 20

cat /var/log/messages

c chat -a /var/log/boot.log

dnf install command-line-assistant

c chat "question"

c chat --interactive

systemctl list-units --type=service --state=running

systemctl status sshd.service

journalctl -u httpd.service --since "1 hour ago"

ps aux --sort=-%mem

head -n 20

cat /var/log/messages

c chat -a /var/log/boot.log

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