Linux Administration Tasks 2

As a Linux administrator, managing systems effectively involves a variety of tasks, from automating jobs with Cron to securing applications. This guide walks you through 24 essential tasks with practical use cases and instructions.

1. Create a Cron Job

Cron automates repetitive tasks. Example: Schedule a backup every day at midnight.

Steps:

1. Edit crontab:
   

   crontab -e

1. Add the job:
   

   0 0 * * * /path/to/backup.sh

1. Verify:
   

   crontab -l

2. Linux Banner

Display a custom message on login using /etc/motd.

Steps:

1. Edit /etc/motd:
   

   echo "Welcome to Linux Server" | sudo tee /etc/motd

3. Linux Collaborative Directories

Set up a shared directory with proper permissions.

Steps:

1. Create directory:
   

   mkdir /shared

1. Set group ownership and permissions:
   

   chgrp developers /shared

   chmod 2775 /shared

4. Linux String Substitute (sed)

Modify files using sed. Example: Replace "error" with "warning".

Command:

sed -i 's/error/warning/g' logfile.txt

5. Linux SSH Authentication

Set up key-based authentication for secure remote access.

Steps:

1. Generate keys:
   

   ssh-keygen

1. Copy the public key to the server:
   

   ssh-copy-id user@server

6. Linux Find Command

Locate files quickly. Example: Find .log files larger than 10MB.

Command:

find /path -type f -name "*.log" -size +10M

7. Install a Package

Install htop as an example.

Command:

sudo apt install htop

8. Install Ansible

Automate IT tasks with Ansible.

Steps:

1. Install Ansible:
   

   sudo apt install ansible

1. Verify:
   

   ansible --version

9. Configure Local Yum Repos

Set up a local YUM repository.

Steps:

1. Create a repo file:
   

   sudo vi /etc/yum.repos.d/local.repo

1. Add content:
   

   [local-repo]

   name=Local Repository

   baseurl=file:///mnt/repo

   enabled=1

   gpgcheck=0

10. Linux Services

Manage services. Example: Start and enable Apache.

Commands:

sudo systemctl start httpd

sudo systemctl enable httpd

11. Linux Configure sudo

Grant sudo privileges.

Steps:

1. Edit sudoers file:
   

   sudo visudo

1. Add user:
   

   username ALL=(ALL) NOPASSWD:ALL

12. DNS Troubleshooting

Diagnose DNS issues.

Commands:

nslookup domain.com

dig domain.com

13. Linux Firewalld Setup

Set up and manage firewalld.

Commands:

sudo firewall-cmd --add-port=80/tcp --permanent

sudo firewall-cmd --reload

14. Linux Postfix Mail Server

Set up Postfix for email delivery.

Steps:

1. Install:
   

   sudo apt install postfix

1. Configure via /etc/postfix/main.cf.

15. Linux Postfix Troubleshooting

Check logs:

sudo tail -f /var/log/mail.log

16. Install and Configure HAProxy LBR

Load balance traffic with HAProxy.

Steps:

1. Install HAProxy:
   

   sudo apt install haproxy

1. Configure /etc/haproxy/haproxy.cfg.

17. HAProxy LBR Troubleshooting

Check status:

sudo systemctl status haproxy

Debug logs:

sudo journalctl -u haproxy

18. MariaDB Troubleshooting

Check MariaDB logs:

sudo tail -f /var/log/mysql/error.log

19. Linux Bash Scripts

Automate tasks. Example: Disk usage report.

#!/bin/bash

df -h > disk_report.txt

20. Add Response Headers in Apache

Enhance security by adding headers.

Steps:

1. Edit .htaccess or /etc/httpd/conf/httpd.conf:
   

   Header set X-Frame-Options "DENY"

1. Restart Apache:
   

   sudo systemctl restart httpd

21. Apache Troubleshooting

Check configuration:

sudo apachectl configtest

View logs:

sudo tail -f /var/log/httpd/error_log

22. Linux GPG Encryption

Encrypt files with GPG.

Commands:

gpg --encrypt --recipient [email protected] file.txt

gpg --decrypt file.txt.gpg

23. Linux Log Rotate

Automate log rotation.

Steps:

1. Configure /etc/logrotate.conf.


2. Test:
   

   logrotate -d /etc/logrotate.conf

24. Application Security

Implement security measures like SELinux, AppArmor, or Fail2Ban.

Commands:

sudo apt install fail2ban

sudo systemctl enable fail2ban

Happy Learning !!!