Linux # System # Management # Configuration # Security

🚁Some basic Linux Commands are:

• reboot | poweroff
• su - | sudo | sudo su
• Navigation : cd | pwd | mv -i | cp -i | rm -i | mkdir -i | rmdir -i | ln
• ls | cat | tac | grep | sort | uniq | xargs | exec | wc | head | tail | more | less | find | cut
• awk | sed | touch | echo | paste
• cmp | comm | diff | sdiff | tee | split | nl
• User Management : id | who | whoami | useradd | usermod | userdel | passwd | groups | chage | chmod | chown | umask | stat
• Process Management : ps | jobs | bg | lsof | kill | killall | systemctl
• Disk Management : du | df | fdisk | parted | blkid | lsblk | lsusb | lsscsi | mount | findmnt
• top | htop | free | iostat | vmstat | netstat | mpstat
• systemctl --failed | systemd-analyze
• Network Management : nmcli | ip | ifconfig | nmtui | ping | dhclient | ss | traceroute | tracepath | nslookup | dig | route | mtr | arp | tcpdump | netstat | ssh | telnet | scp | curl | wget | nc
• hostname | hostnamectl | uname | env |
• Text file format converters : dos2unix | unix2dos
• Package Management: rpm | yum | dnf
• dmidecode | lscpu | lspci
• history
• date | time
• Archive Management : tar | gzip | bzip2
• vi | vim | nano
• Absolute and Relative Path (/)
  • ~
  • . and ..
• ./ (to execute command) | sh
• Advanced Linux Commands
  • Find & exec & xargs
• bash-completion utility

🚁User & Group Management

notes

• su #Switching users
• sudo #Executing commands as another user. Group = [wheel | sudo]
• sudo su
• newgrp #Switching user groups
• Users Management
  • Creating Users | Modifying User Accounts (Add | Remove user from group) | Reset Users (Default Setting) | Deleting Users
  • Locking and Unlocking User Accounts | Expiring User Accounts | User Password Management | Changing User Shell | Viewing User Information | Permission & Access Control Lists (ACLs) | Managing User Quotas | User Account Policies
• Group Management
  • Creating Groups | Modifying Groups Accounts (Add | Remove user from group) | Deleting Groups

➡️user

Script:

➡️user add bulk

➡️user setpasswd bulk

➡️user_addgroup bulk_sudo

🚁 File & Folder | Permission

Notes

➡️file & folder permission

🚁 System Hardware & Device

• check OS version #cat /etc/*release
• check the kernel version #uname -a
• #hostnamectl
• kernel parameters cat /proc/cmdline

Notes

➡️[system hardware ]

🚁 Performance

Notes

• CPU
• Memory
• Disk I/O
• Network
• Process
• System Performance
• File System and Disk
• Kernel and System Tracing
• Performance Profiling
• Benchmarking

🚁 SystemD (Service & Process)

Notes

➡️SystemD - Website

➡️Service | Ports | Process

🚁 Network

Notes

➡️ Network

🚁 FirewallD

Notes

➡️ FirewallD

🚁 Schedule - Cron

Notes

🚁 Linux Logs

Notes

➡️ log

• Keywords

  • Date & Time
  • Activity
  • Errors, warnings, and critical alerts
  • Service and application failures
  • Security-related incidents (failed logins, suspicious user activity)
  • Performance bottlenecks or memory/disk-related problems
  • Unusual network activity (e.g., port scans, blocked IPs)
  • Hardware malfunctions (disk, CPU, RAM)

• Parsing Log Files

  • Tools for Parsing Logs; There are several command-line tools and programming languages that can help with log parsing:
    • grep: For searching text in logs.
    • awk: For pattern scanning and processing.
    • sed: For stream editing and transformations.
    • cut: For extracting specific fields.
    • logwatch: For summarizing log file information.
    • Python with libraries like pandas, json, and re: For advanced parsing.
    • Regex (Regular Expressions)

🚁 Vi

Notes

➡️ Vi

🚁 Port Number

Notes

➡️ Ports Number

🚁 Troubleshooting

Method

• Recent Change (Narrow Down the Issue)
• Symptom | Error Massage
• Log File (Error Pattern | Timing) - Parsing Log Files
• Configuration Validation
• Dump file
• Compare / Replicate / Simulate a problem with a working system that running the same distribution and version
• Check to see whether the problem is reproducible
• Common troubleshooting
• Symptom, Diagnosis, Solution
• Document findings, actions, and outcomes

Notes

➡️notes

🚁 Productivity

• bash-completion

🚁 RHEL

• Subscription
• Insights
• Satellite
• Ansible

🚁 HomeLab

Linux

• Linux load balancing
  • network interface card (NIC) bonding
  • services to HTTP and TCP-based services
• Integrating Linux user authentication with Windows Active Directory (AD) using the System Security Services Daemon (SSSD)
• SLURM (Simple Linux Utility for Resource Management)
• Configure NFS Shares
• Basic Web Server - Apache

🚁 References

• https://www.certdepot.net
• https://www.tecmint.com
• https://www.geeksforgeeks.org
• https://www.javatpoint.com
• https://linuxjourney.com
• https://www.open-scap.org/
• https://www.cisecurity.org/cis-benchmarks
• https://www.cyberciti.biz/
• https://killercoda.com
• https://linuxsecurity.com/
• https://firecracker-microvm.github.io/
• https://www.redhat.com/en/interactive-labs

🚁 Linux Security

• Industry Standard (General)
  • CIS Benchmark (Center for Internet Security)
  • STIG Standard (Security Technical Implementation Guide)
    • Federal Information Processing Standard (FIPS)
    • SELinux
• Hardening (Securing systems by applying configurations, controls, and best practices that minimize potential vulnerabilities)
• Vulnerability Scanning and Patching
  • Security Technical Implementation Guides (STIGs) Viewer
  • Security Content Automation Protocol (SCAP) Compliance Checker
• Baseline, Guide and Best Practice
• Risk Compliance
• Authentication: Identity and access management (IAM) & Privileged Access Management (PAM)
  • Centralized Authentication (LDAP, Active Directory)
  • Decentralized Authentication (local user accounts)
• Linux Audit Framework
  • AuditD

🚁 Socratic Linux Administration

➡️ Socratic Linux Administration

🚁 RHCSA

➡️ RHCSA Objectives

➡️ RHCSA

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🚁 CheatSheet

➡️ CheatSheet