Day 05: Permissions Architecture, Users & Process Signals

Day 05 · Lunch — Permissions Architecture, Users & Process Signals

⚡ 60-Second Mental Model (Student Digest)

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║  ZOTHOS × 1NC0GN30 // LINUX FILESYSTEM & SHELL EXECUTION ARCHITECTURE       ║
╠══════════════════════════════════════════════════════════════════════════════╣
║                                                                              ║
║   [ USER TERMINAL / TUI ]  ──( stdin 0 )──►  [ BASH / ZSH SHELL PARSER ]     ║
║                                                       │                      ║
║                                              ( glibc / syscalls )            ║
║                                                       ▼                      ║
║   [ VFS / INODE TABLE ]    ◄───────────────  [ LINUX KERNEL RING 0 ]         ║
║     ├── /bin  (Core Binaries)                  ├── Process Scheduler         ║
║     ├── /etc  (System Configs)                 ├── Memory Manager            ║
║     ├── /home (Operator Workspaces)            └── Netfilter / I/O           ║
║     └── /var  (Logs & Runtime State)                                         ║
╚══════════════════════════════════════════════════════════════════════════════╝

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Welcome to Day 5 Lunch! Today, we will dive deeper into advanced process management and system monitoring techniques. We'll cover enhanced commands, filtering and customizing output, and analyzing system logs.

Advanced Process Management (htop, pstree)

Description: htop and pstree offer more detailed and interactive ways to view processes and their hierarchies.

Basic Usage:

- htop - Launch an interactive, color-coded process viewer. You can navigate using arrow keys and manage processes interactively.
- pstree - Display processes in a tree-like format, showing parent-child relationships.

Advanced Usage:

- htop -u username - Filter htop to show processes for a specific user.
- pstree -p - Include process IDs in the tree view.
- htop -d 10 - Set htop to update every 10 seconds.

Detailed Resource Monitoring (sar, atop)

Description: sar collects and reports system activity, while atop provides detailed historical performance data.

Basic Usage:

- sar -u 5 3 - Report CPU usage every 5 seconds for 3 iterations.
- sar -r - Display memory usage statistics.
- atop - Start atop for real-time and historical performance monitoring.

Advanced Usage:

- atop -r - Read from atop logs for historical analysis.
- sar -q - Report queue length and system load.

Customizing Output (grep, awk, sed)

Description: Use grep, awk, and sed to filter, format, and manipulate command output for analysis.

Basic Usage:

- grep 'pattern' - Search for lines matching 'pattern' in command output.
- awk '{print $1, $2}' - Format output by extracting specific columns.
- sed 's/old/new/' - Replace occurrences of 'old' with 'new' in output.

Advanced Usage:

- top -b -n 1 | grep 'PID' - Filter top output to show only lines containing 'PID'.
- ps aux | awk '{print $1, $11}' - Display user and command name from ps output.
- vmstat 5 | grep 'procs' - Filter vmstat output to show only lines containing 'procs'.

Analyzing Logs (logwatch, syslog)

Description: logwatch summarizes system logs, and syslog provides a standardized way to log system messages.

Basic Usage:

- logwatch --detail high --service all - Generate a detailed log report for all services.
- tail -f /var/log/syslog - Continuously monitor the syslog file for new messages.

Advanced Usage:

- logwatch --range 'yesterday' - Report on logs from the previous day.
- tail -f /var/log/messages - Monitor general system messages.

System Performance (perf, dstat)

Description: perf and dstat are tools for performance analysis and monitoring.

Basic Usage:

- perf top - Real-time performance monitoring and profiling.
- dstat -cdngy - Display CPU, disk, network, and system statistics.

Advanced Usage:

- perf record -e cpu-clock -a sleep 10 - Record performance data for 10 seconds.
- dstat --vm --io - Show VM and I/O statistics.

Key Takeaways

htop: An interactive tool for viewing processes, allowing real-time management and filtering.

pstree: Visualizes processes and their hierarchy, helping understand parent-child relationships.

sar: Collects and reports detailed system activity, useful for performance analysis over time.

atop: Provides comprehensive monitoring of system resources, including historical data.

grep, awk, sed: Essential tools for filtering, formatting, and manipulating command output for deeper analysis.

logwatch: Summarizes and analyzes system logs, helping in quick reviews of system activities.

syslog: A standard for logging system messages, crucial for monitoring and troubleshooting.

perf: Performance profiling tool that helps analyze and optimize system performance.

dstat: Provides versatile resource monitoring, offering real-time insights into system performance.

By mastering these commands and techniques, you'll gain a comprehensive understanding of process management and system monitoring, enabling you to effectively analyze and troubleshoot system performance issues.

Happy learning and exploring!

Day 05 · Dinner — Permissions Architecture, Users & Process Signals

⚡ 60-Second Mental Model (Student Digest)

╔══════════════════════════════════════════════════════════════════════════════╗
║  ZOTHOS × 1NC0GN30 // LINUX FILESYSTEM & SHELL EXECUTION ARCHITECTURE       ║
╠══════════════════════════════════════════════════════════════════════════════╣
║                                                                              ║
║   [ USER TERMINAL / TUI ]  ──( stdin 0 )──►  [ BASH / ZSH SHELL PARSER ]     ║
║                                                       │                      ║
║                                              ( glibc / syscalls )            ║
║                                                       ▼                      ║
║   [ VFS / INODE TABLE ]    ◄───────────────  [ LINUX KERNEL RING 0 ]         ║
║     ├── /bin  (Core Binaries)                  ├── Process Scheduler         ║
║     ├── /etc  (System Configs)                 ├── Memory Manager            ║
║     ├── /home (Operator Workspaces)            └── Netfilter / I/O           ║
║     └── /var  (Logs & Runtime State)                                         ║
╚══════════════════════════════════════════════════════════════════════════════╝

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Welcome to Day 5 Dinner! Tonight, we'll build upon the concepts covered in breakfast and lunch, and dive even deeper into advanced process management and system monitoring. This session will review the topics covered earlier and introduce new techniques and tools to further enhance your understanding.
Dinner Agenda:

Review of Breakfast and Lunch Topics
Advanced Process Control
In-Depth System Monitoring Techniques
Hands-On Advanced Challenges

Detailed Overview and Advanced Topics
1. Review of Breakfast and Lunch Topics

Breakfast Review:

Process Management: Covered ps, top, htop, and pstree for viewing and managing processes. Focused on real-time monitoring and process filtering.

Lunch Review:

System Resource Monitoring: Examined sar for historical data and atop for real-time metrics. Also, discussed output customization with grep, awk, and sed.

2. Advanced Process Control

Advanced kill and pkill:

Process Signals: Learn more about different signals you can send with kill. For example, SIGSTOP to pause a process and SIGCONT to resume it.
Using pkill with Patterns: You can use regular expressions with pkill to match process names more flexibly.

Examples:

bash

kill -STOP 1234 # Pause process with PID 1234
kill -CONT 1234 # Resume process with PID 1234
pkill -f 'java.' # Kill all processes matching 'java.' pattern
pkill -9 -f 'pattern' # Force kill processes matching 'pattern'

Process Priorities with nice and renice:

nice: Launch processes with adjusted priority.
renice: Change the priority of already running processes.

Examples:

bash

nice -n 10 command # Run 'command' with a nice value of 10
renice -n -5 -p 1234 # Change priority of process with PID 1234 to -5

3. In-Depth System Monitoring Techniques

Advanced sar Usage:

Custom Reports: Generate specific reports for CPU, memory, and network usage using sar.
Combining Metrics: Use sar to combine multiple metrics into a single report.

Examples:

bash

sar -u 1 3 # Report CPU usage every 1 second for 3 times
sar -r 1 3 # Report memory usage every 1 second for 3 times
sar -n DEV 1 3 # Report network statistics every 1 second for 3 times

Enhanced atop Features:

Historical Data Analysis: Analyze data collected by atop for historical performance insights.
Using atop Filters: Apply filters to focus on specific types of resources.

Examples:

bash

atop -r /var/log/atop/atop.log # Read from atop log file
atop -b -n 10 # Display real-time stats for 10 seconds

Customizing dstat:

Combining Metrics: Use dstat to show combined metrics such as CPU, memory, disk I/O, and network.

Examples:

bash

dstat -cdngyt # Display CPU, disk, network, and system stats with timestamps
dstat --top-cpu # Show the top processes by CPU usage

4. Hands-On Advanced Challenges

Challenge 1: Advanced Process Control

Task: Use htop to identify and renice the top 3 processes consuming the most CPU. Save the output to a file.
Command:

bash

htop

In htop, sort by CPU usage, renice the top 3 processes, and save output using a screen capture or htop command options

Challenge 2: Comprehensive sar Report

Task: Collect CPU, memory, and network usage data using sar and generate a report combining these metrics.
Commands:

bash

sar -u 1 3 > cpu_usage.txt
sar -r 1 3 > mem_usage.txt
sar -n DEV 1 3 > net_usage.txt
cat cpu_usage.txt mem_usage.txt net_usage.txt

Challenge 3: Analyzing atop Logs

Task: Review atop logs for CPU and memory usage spikes and identify any anomalies.
Commands:

bash

atop -r /var/log/atop/atop.log