Cheatsheet

1. Add new user and database to Mysql

    Create database ‘<database>’;
    CREATE USER '<user>'@'localhost' IDENTIFIED BY 'password';
    GRANT ALL PRIVILEGES ON <database>.* TO <user>@‘localhost';
    FLUSH PRIVILEGES;
   

   • Enable logging without restarting

     SET GLOBAL general_log = 'ON';
     SET GLOBAL slow_query_log = 'ON';
     

   • Disable runtime logging

     SET GLOBAL general_log = 'OFF';
     SET GLOBAL slow_query_log = 'OFF';
     

   • https://www.pontikis.net/blog/how-and-when-to-enable-mysql-logs

2. List listening ports

   netstat -plntu | grep -i "listen"
   

3. Docker

   • Update after files change

     docker-compose up -d --build
     

   • Logs

     docker-compose logs -f -t
     

   • Destroy all docker images

     docker stop $(docker ps -a -q) 
     docker rm $(docker ps -a -q)
     docker rmi $(docker images -q) 
     docker exec <name> <command>
     

4. Mailgun Setup

    apt-get update 
    apt-get install postfix libsasl2-modules
   

   • Add to /etc/postfix/main.cf

      smtp_sasl_auth_enable = yes
      relayhost = smtp.mailgun.org        
      smtp_sasl_security_options = noanonymous
      smtp_sasl_password_maps=hash:/etc/postfix/sasl_passwd
     

    echo 'smtp.mailgun.org <mail>:<password>' > /etc/postfix/sasl_passwd
    chmod 600 /etc/postfix/sasl_passwd
    postmap /etc/postfix/sasl_passwd
    service postfix restart
    sudo apt-get install -y mailutils
    echo "Mail test" | mail -s "Subject" root
    echo "This is testing SMTP Relay." | mail -s "Postfix Mailgun" $MAIL
   

5. Send mail on every sudo command

    visudo -f /etc/sudoers.d/my_sudoers
    Defaults mail_always
    Defaults mailerpath=/usr/sbin/sendmail
    Defaults mailto="root"
    Defaults mailerflags="-t"
   

6. Hibernate Mac -> Here

7. Find blogger feed url - add this to end

   /feeds/posts/default?alt=rss
   

8. Download all files in directory

   wget - r - np -nH cut-dirs -R index.html http://hostname/aaa/bbb/ccc/ddd
   

9. Generate dhparam

   openssl dhparam -dsaparam -out /etc/ssl/private/dhparam.pem 4096
   

10. Check system logs for a service

    journalctl -u <service.name> -f
    

11. Remove commited directories from git remote branch

    git rm -r --cached some-directory
    git commit -m 'Remove the now ignored directory "some-directory"'
    git push origin master
    

12. Setup rTorrent with ruTorrent
    • Click here
13. Jekyll

    • Run on custom host

       bundle exec jekyll serve -H 10.8.0.1
      

14. Nmap

    • Scan for open ports

      nmap -sS -sU -PN -p 1-65535 thedoc.eu.org
      

15. Open port on SSH

    ssh -L <localPort>:127.0.0.1:<remotePort> sshConfig
    

16. UFW

    • Allow from specific subnet

      sudo ufw allow from <subnet/24> to any port <port-no>
      

    • Delete rule

      sudo ufw delete allow <port>
      

    • https://www.digitalocean.com/community/tutorials/ufw-essentials-common-firewall-rules-and-commands

17. To add users to a group

    sudo usermod -aG <grp_toadd> user
    sudo chmod g+rw <folder>
    

18. Forward SSH port to localhost

    ssh -L <localPort>:localhost:<remotePort> <server_config>
    

19. Change text in any file using bash/sed

    sed -i 's/original/new/g' file.txt
    

20. Repeat a command in bash every n seconds

    while :; do clear; <command> ; sleep < n seconds >; done
    

21. Adb commands to control package manager

    pm list packages
    pm path package.name
    adb install -r package.apk
    pm disable --user 10 package.name
    

22. Android Studio : Solve support library issue
    • Execute in Terminal ./gradlew -q dependencies app:dependencies
    • Then search for conflicting dependencies version
    • add the latest version for conflicting dependencies explicitly in build.gradle