README.md

System Administration Tasks

General Tips

• Always verify your task using one or more of the approaches below:
  • Use Curl command to the test the task. This is particular useful for verifying tasks that involve HTTP/S servers e.g. Apache, Nginx, Firewalld, Iptables. Usage is: curl <HTTP URL>. Examples:
    • Simple URL fetch: curl http://stapp01:8080/. You should get a valid HTML content returned back.
    • Check HTTP headers (Especially useful to verify tasks that involve restricting access) curl -I http://stapp01:8080/. You should see a valid HTTP Header with HTTP Return code.
    • To ignore any certificate errors and still fetch the content, use option -k curl -k http://stapp01:8080/ or curl -Ik http://stapp01:8080
    • To connect as a specfic user (checking PAM or Htaccess tasks): curl -u javed:ax23Xsdg http://stapp01:8080/ ('javed' is the user and 'ax23Xsdg' is the password)
  • You can also use Telnet to verify connectivity to a specific port: telnet stapp01 8080. Ensure that you do not see any connection errors.
  • For some tasks, you need to use browser by clicking Open Port on Host 1 tab to open the site on specific port (especially the Wordpress task)
  • For tasks that involve iptables, use iptables -nvL to list all the rules in a simple-to-understand format
  • For some tasks, it may be time-saving and less error-prone if you rather create a shell script, with all the required commands, offline using your favourite IDE. This is how you will actually perform tasks in real-world. You can then copy-paste the script to each required host and execute it. This will help you to easily go for bonus points. e.g. Tasks that require you to configure Iptables or Firewalld
  • Most of the Linux tasks are based on Centos environment. Hence you can make use of the free Katakoda Centos Playground to practice changes. This is pretty useful for tasks that involve Httpd, Nginx, MariaDB, PostgreSQL, Firewalld or Iptables. This maximizes the learning process. So the recommendation is to:
    • Open the task in Kodekloud Engineer, note down the question and press Try Later
    • Open KataKoda Playground and play around until you are confident to attempt the question
    • Reopen question in Kodekloud Engineer, and follow the same approach
    • Note:
      • To find out the OS Flavor and version, run cat /etc/*release*
      • Centos Playground will allow processes such as httpd to listen only on port 8080
      • You can access browser by click Opening Port on Host 1 similar to KKE
      • For similar environment on Ubuntu, Katakoda Ubuntu Playground

Common mistakes

• Not reading the question properly. Especially, when you redo the same question, all the names and port values would've changed in the new question. So pay attention to that.
• To restart a systemd service after performing changes (like nginx.conf,httpd.conf, sshd.config), you run sudo systemctl restart <service> and not sudo systemctl start <service>. The problem with using start option is, if the service is already running then nothing is done. So your changes never take effect.
• For Firewalld tasks, most people miss out on reloading the firewall rules by running sudo firewall-cmd --reload
• For Iptables tasks, forgetting to persist the iptables rules is another common mistake: sudo service iptables save

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For general tips on getting better at KodeKloud Engineer tasks, click here