NETSTAT

sudo netstat -nap | grep nginx

netstat -an | grep :1935 | grep ESTABLISHED | wc -l ## Returns # connections

netstat -tulpn 

netstat -tulpn | grep :80

NETWORKING

dig lookup
dig +short mx example.com
dig +short ns example.com

PSQL

# login as postgres user
psql -U postgres

# list all databases
psql -l

# quit
\q

# connect to db
\c database

# show tables
\dt

# list users
\du

TMUX

sudo apt-get update
sudo apt-get install tmux

• tmux list-sessions
• Ctrl-b then d - To detach
• tmux attach -t <session-name> - To attach

UBUNTU

tar -zxvf name.tar.gz
unzip dev.zip
apt get unzip

• echo "stuff" > README.md - write / overwrite file
• echo "add stuff" >> README.md - append to file
• ps axuf - process status displays information of all active processes
• ps -e - displays all the current process
• sudo /usr/local/nginx/sbin/nginx -s restart
• sudo /usr/local/nginx/sbin/nginx -s reload
• lsof -wni tcp:3000 - find process on port 3000
• kill -9 <pid> - kills process of process # pid
• cat / head / tail filename.txt - displays entire / start / end of file
• echo hello > foo.txt - redirect into file, creates file if not exist, overwrites if exists
• echo hello >> foo.txt - appends to file
• grep my_regrex my_file - search and returns whole line of file for each match
• grep -i my_regex my_file - -i makes the search case insensitive.
• grep -v my_regex my_file - return all lines that don’t contain my_term. -vreturns the inverse, like not in many languages.
• grep -c my_regex my_file - return a count of how many times a match is found with -c.
• grep -R my_regex my_folder - recursively search all files in the folder and all subfolders with -R.
• ag my_regex my_file - returns the line number and the line with any matches.
• ag -i my_regex my_file -  -i for case insensitive .