linux-command-cheatsheet

Some useful linux commands

Working the Servers

To start the a simple http server at a single line:

python -m SimpleHTTPServer 8080

To see if a server is listening at a particular port:

lsof -i:8080

Working with Programs

To run a Java jar program as a background process:

nohup java -jar myProgram.jar 1>/dev/null 2>/dev/null &

To check if a Java program is running:

ps aux | grep -v myProgram.jar | grep -v grep

To check what program is running and listening at a partcular port (say 8080):

lsof -i:8080

To kill a process (say a Java process myProgram.jar):

kill -9 `ps aux | grep myProgram.jar | grep -v grep | awk 'NR==1{print $2}'`

To skill a GUI program (after that point and click on the gui to force close it):

xkill

Working with Security

To see the current status of linux security:

sudo getenforce

To turn off the linux security:

sudo setenforce 0

To turn on the linux security:

sudo setenforce 1

Passwordless ssh

Configure passwordless ssh from the machine-A to machine-B by performing the following steps:

• step 0: login machine-A and run "ssh-keygen -t rsa"

• Step 1: login machine-B to to $HOME

• Step 2: run "mkdir .ssh"

• Step 2: touch .ssh/authorized_keys"

• Step 3: run "sudo chmod 700 .ssh"

• Step 4: run "sudo chmod 640 .ssh/authorized_keys"

• Step 5: login onto machine-A and cd to $HOME

• Step 6: run "cat .ssh/id_rsa.pub | ssh machine-B 'cat >> .ssh/authorized_keys'"

Alternatively, you can run ssh-copy-id which is one-step only

Working with directories

The following script print the full path of the directory containing the bash script being executed:

#!/usr/bin/env bash
dir_name=`dirname "${BASH_SOURCE-$0}"`
pwd=`pwd`
current_dir=$pwd/$dir_name

echo $current_dir