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Vivesh
Vivesh

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Linux Administration Tasks 2

#linux #cloud #devops #learning

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
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  1. Add the job: 
 0 0 * * * /path/to/backup.sh
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  1. Verify: 
 crontab -l
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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
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3. Linux Collaborative Directories

Set up a shared directory with proper permissions.

Steps:

  1. Create directory: 
 mkdir /shared
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  1. Set group ownership and permissions: 
 chgrp developers /shared chmod 2775 /shared
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4. Linux String Substitute (sed)

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

Command:

sed -i 's/error/warning/g' logfile.txt
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5. Linux SSH Authentication

Set up key-based authentication for secure remote access.

Steps:

  1. Generate keys: 
 ssh-keygen
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  1. Copy the public key to the server: 
 ssh-copy-id user@server
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6. Linux Find Command

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

Command:

find /path -type f -name "*.log" -size +10M
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7. Install a Package

Install htop as an example.

Command:

sudo apt install htop
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8. Install Ansible

Automate IT tasks with Ansible.

Steps:

  1. Install Ansible: 
 sudo apt install ansible
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  1. Verify: 
 ansible --version
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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
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  1. Add content: 
 [local-repo] name=Local Repository baseurl=file:///mnt/repo enabled=1 gpgcheck=0
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10. Linux Services

Manage services. Example: Start and enable Apache.

Commands:

sudo systemctl start httpd sudo systemctl enable httpd
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11. Linux Configure sudo

Grant sudo privileges.

Steps:

  1. Edit sudoers file: 
 sudo visudo
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  1. Add user: 
 username ALL=(ALL) NOPASSWD:ALL
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12. DNS Troubleshooting

Diagnose DNS issues.

Commands:

nslookup domain.com dig domain.com
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13. Linux Firewalld Setup

Set up and manage firewalld.

Commands:

sudo firewall-cmd --add-port=80/tcp --permanent sudo firewall-cmd --reload
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14. Linux Postfix Mail Server

Set up Postfix for email delivery.

Steps:

  1. Install: 
 sudo apt install postfix
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  1. Configure via /etc/postfix/main.cf.

15. Linux Postfix Troubleshooting

Check logs:

sudo tail -f /var/log/mail.log
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16. Install and Configure HAProxy LBR

Load balance traffic with HAProxy.

Steps:

  1. Install HAProxy: 
 sudo apt install haproxy
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  1. Configure /etc/haproxy/haproxy.cfg.

17. HAProxy LBR Troubleshooting

Check status:

sudo systemctl status haproxy
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Debug logs:

sudo journalctl -u haproxy
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18. MariaDB Troubleshooting

Check MariaDB logs:

sudo tail -f /var/log/mysql/error.log
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19. Linux Bash Scripts

Automate tasks. Example: Disk usage report.

#!/bin/bash df -h > disk_report.txt
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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"
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  1. Restart Apache: 
 sudo systemctl restart httpd
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21. Apache Troubleshooting

Check configuration:

sudo apachectl configtest
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View logs:

sudo tail -f /var/log/httpd/error_log
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22. Linux GPG Encryption

Encrypt files with GPG.

Commands:

gpg --encrypt --recipient email@example.com file.txt gpg --decrypt file.txt.gpg
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23. Linux Log Rotate

Automate log rotation.

Steps:

  1. Configure /etc/logrotate.conf.
  2. Test: 
 logrotate -d /etc/logrotate.conf
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24. Application Security

Implement security measures like SELinux, AppArmor, or Fail2Ban.

Commands:

sudo apt install fail2ban sudo systemctl enable fail2ban
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Happy Learning !!!

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