User:Cyrusty/Useful Commands

Linux Commands

cd # Home directory or changes directory

cd .. # Up a directory and to up 2 directories ../.. and so on

cd - # Returns you to the previous directory you were in

cd / # Changes directory to root

cd /proc # Changes directory to your running processes

ls # Lists the files that are in a directory

ls –a # Shows all files/hidden files in a directory

ls –al # Shows all files/hidden files and time/write permissions in a directory

ls -alh # Shows same as above command but shows file sizes in a better readable format

ls -l # Shows the files and write permissions in the directory

ls / # Shows the contents of the root directory

cat <file name. extension> # Prints the contents of a file on the shell

mkdir <Directory Name> # Makes a directory

mkdir -p EXAMPLE/RIGHT/IN/HERE # Makes multiple folders in the directory created

mv /FILE/NAME/OR/DIR /TO/DIR/WANTED # Moves a file to a directory or renames a file

rm <FILE NAME> # Removes a file

rmdir <DIRECTORY> # Removes an empty directory

rm –r # Removes a directory and its contents

rm -rf # Force deletes everything

rm –rf / # Deletes everything under root directory

sudo # Runs command as sudo

sudo bash # Changes to root privellages

sudo su # Gives SUPERUSER privellages

sudo !! # This will redo the previous command but instead runs it as sudo

su # switch USER

adduser USERNAME # Create a USER

adduser USERNAME sudo # Adds USER to the sudo group

passwd # Reset password for current user

man <COMMAND> # Displays a manual for a specific command

man hier # Displays a description of the filesystem hierarchy

grep # searching, finding, filtering command

top # Shows running processes

htop # Shows more information than top and in more detail

sudo renice -10 PID # This will prioritize a process (-20 being highest priority and 19 being lowest priority)

ps -A # Shows all running processes

kill PID # Kills process under a certain PID

kill -9 PID # Force kills a process that wont kill normally

sudo killall NAME # Kill all processes under the NAME

sudo pkill -u USER # Kills all USER processes

head FILENAME # Prints the first 10 lines

tail FILENAME # Prints the last 10 lines

clear # Clears the screen

pwd # Print working directory

<file name. extension> # Makes a file in current directory ##unsure of this##

cal # Shows current calender date (also cal mm/yy)

whatis # Type a command after to see a brief description of what it does/is

who # Shows current users on the machine and when they logged in

w # Shows whos logged in, from where, how long and what they're doing

nano # Edit a text file

vi # Nano is better...

vim # Another editor... type vimtutor on commandline to learn more

sort # Sort lines of text files

wc # Wordcount a text file

rig # Random Identity Generator

apt-cache search # ??

Networking

ifconfig # Shows network info IP/MAC address

sudo netdiscover # Shows who's on the network and identifies the ip address of each connection

sudo lsof -i # Lists the open ports and the process that owns them (to see which process is bound to port use :PORTNUMBER)

sudo netstat # Seeing what might be exposed to the network

sudo netstat -tulpn # t=tcp, u=udp ports, l=listening ports, p=processes, n=numerical

sudo macchanger -s enp4s0/eth0/wps/ # To see mac addresses

sudo macchanger -r enp4s0 # Changes the current mac address to a new one

ssh -NCD 1080 user@ip # Proxy network traffic over port 1080 (edit below settings on firefox to port traffic correctly)

Manual Proxy Configuration

Socks Host: localhost

port: 1080

SSH

ssh-keygen -t rsa # creates a key in .ssh

sudo nano /etc/ssh/sshd_config # change ssh parameters (key logging/password authentication)

sudo service ssh restart # saves ssh modifications

ssh-copy-id USER@IP # saves the pub key to be known as an authenticated key

scp -r USER@IP:/home/USER/FILE/FOLDER /home/user/localmachine # copy from server to localmachine

scp -r /home/USER/localmachine/file/folder USER@IP:/home/USER/VPS # copy files from localmachine to server

sudo hostname -b NEWHOSTNAME # Renames the host

sudo nano /etc/hosts # Set unique names for IP's (makes shelling in faster using a desired name) eg. 172.321.123.123<TAB>VPS1

sudo apt-get install openssh-server # allows access to ssh into the computer through a LAN

System Info

df # Displays mounted devices

dmidecode | less # Shows bios information

lscpu # Shows cpu/hardware information

lspci # List all PCI devices

lsusb # List all USB devices

lsblk # List all Hard disks, Cd drives etc

cat /proc/meminfo # Shows memory information

cat /proc/version # Shows current running kernal version

Shutdown/Reboot

shutdown -r +60 # restarts in 60mins

shutdown -h +60 # shutdown in 60mins

poweroff # shuts system down

reboot # restarts computer

init 6 # same as reboot

Account Management

useradd # Adds a user

useradd -m -d # Create a new user and makes a home directory for the user and define the home directory /home/DIR/FOR/USER

sudo adduser <username> sudo # adds user to sudo privileges

userdel # Deletes a user

usermod -L USER # Locks the user from logging in

usermod -U USER # Unlocks the user so they can log in again

tail /etc/shadow

tail /etc/passwd

tail /etc/group

Note users will have a "!" after their name if they are locked out of their account to check this type in the above shadow command

File Permissions

(R)ead=4

(W)rite=2

(X)ecute=1

d=directory

l=link

4+2+1 = (r+w+x) = 7

4+2 = (r+w) = 6

4+1 = (r+x) = 5

4 = (r) = 4

2+1 = (w+x) = 3

2 = (w) = 2

1 = (x) = 1

chmod xxx dir # Change all files in a single directories permissions

chmod -R xxx dir # Change all file/folders permissions recursively

chown owner:group DIRECTORYNAME # Changes the owner and group name of files

Mail

mail # Checks mail for current user

mail -s "SUBJECT" USER < /home/USER/test.text # sends a mail to the user with test.text as the body

mail -f USER # Checks mail for selected user

mail -f guest # checks guest messages

Piping & Redirection

cat /FILE/IN/A/DIRECTORY | less # Shows in a opened document view without clogging the terminal

cat /FILE/IN/A/DIRECTORY | espeak # Speaks the text document in linux voice

Git

git add . # add all files for committing

git commit -am "COMMIT MESSAGE" # commit the changes locally

git push origin master # push changes to the server

git remote remove origin # Removes origin master

System Commands & Services

sudo apt-get update && sudo apt-get install # Updates n upgrades system to latest

crontab -e # the crontab (short for "cron table") is a list of commands that are scheduled to run at regular time intervals on your computer system

sudo nano /etc/default/grub # change grub options (boot timer)

cpulimit -b -l <PERCENTAGE> -p <PID> # Install cpulimit and use this command to restrict the amount of resources a program will use

Crontab Script Commands

@reboot sudo macchanger -r enp4s0 # (or eth0) # changes to random mac address on each reboot

@reboot sleep 20 && sudo shutdown 60 # will wait 20mins then schedule a shutdown 60mins later (just put this down as a reminder for sleep in crontab)

*  *    * * *   python3 /home/USER/ddns.py DNS 67f0ce616739484f82ca3837f40b401f # This will run the ddns.py script every 1 minute to detect if the ip changes and will update the domain (so the domain always points to the current ip address of the lappie/pc (of the router actually).

^The ddns.py script can be found here

Handy things to remember

ln -s /PATH/TO/SOMETHING/REAL /usr/local/bin/NAMEWANTED # can use executable file with preferred bind name

CTRL r # to search for previously used COMMAND

CTRL p # shows previously used COMMAND

CTRL a # brings you to begin of line

CTRL e # brings to the end of line

tail -f FILENAME # this will follow the file while it's being edited

echo "some kind of text" > example.text # this will overwrite the .text file with the quoted line

echo "new line of text" >> example.text # this will write the quoted line on a new line

alias COMMANDNAME="DESIREDNAME" # this will temporarily save a command to the desired name

echo "alias COMMANDNAME=\"DESIREDNAME\";" >> ~/.bashrc # this will permanently save a desired command to the bash file

&& # chain commands together

convert example.png example.jpg book.pdf # Converting files to PDF

> means to overwrite
>> means to append

Examples of Things

ls -alh /home/user/some/random/place >> ANYNAME # cat ANYNAME to see it show the directory with info

grep WHATEVERSEARCHINGFOR ./* # Useful for findings things.. If successful this will print out what it finds in the shell

Random Password Generators

openssl rand -base64 32 # generates random 32 character password

</dev/urandom tr -dc 'A-Za-z0-9!"#$%&'\''()*+,-./:;<=>?@[\]^_`{|}~' | head -c 10 ; echo # Sauls random character/symbol generated password command