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

• List listening ports

netstat -plntu | grep -i "listen"

1. 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>
   

2. Mailgun Setup

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

3. Add to /etc/postfix/main.cf

   bash 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
   

4. 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"
   

5. Hibernate Mac

6. Find blogger feed url - add this to end

   /feeds/posts/default?alt=rss
   

7. Download all files in directory

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

8. Generate dhparam

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

1. Check system logs for a service

   journalctl -u <service.name> -f
   

2. Remove commited directories from git remote branch

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

3. Setup rTorrent with ruTorrent

   • Click here

4. Jekyll

   • Run on custom host

   bundle exec jekyll serve -H 10.8.0.1
   

5. Nmap

   • Scan for open ports

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

6. Open port on SSH

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

7. 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

8. To add users to a group

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

9. Forward SSH port to localhost

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

10. Change text in any file using bash/sed

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

11. Repeat a command in bash every n seconds

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

12. Adb commands to control package manager

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

13. 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