* Reference:
** Basics:
*** Getting help:

# View the manual for target command man command

# Get help with a target command (probably the same as above, but not always): command -h

# In case you forget the name of a command, print possible commands relating to any given word: apropos word

# View index of help pages: info *** Command Line Utilities:
**** Basic File and Directory Operations:
# Print current working directory: pwd # Show files in current directory: ls # Show maximum information about all files, including hidden: ls -a

# Recurse into subdirectories and list those as well: ls -R

# List files by modification time, most recent first. ls -lt

# Move/rename a file or directory (be careful that you don't move the source over a destination with the same name): mv source destination

# Delete target forever (be very careful), use -r recursive flag for directories: rm target

# Copy file or directory: cp source destination

# Mount filesytem: mount /dev/device_name /media/device_name

# Unmount: umount /media/device_name

# Forensically clone filesystems and do other low-level operations on files. Be careful with this one. Can be destructive: dd # Work with disk partitions: parted # Filesystem creation tool: mkfs **** System Administration:

# Execute command as an administrator (can be destructive/insecure. Use only for system administration tasks): sudo command

# Become system administrator: sudo -s

# Quit system administration: exit # Forgot to type sudo in front of a command and already hit enter? Repeat the last command using sudo: sudo !!

***** Installing software from a .tgz (also known as a tarball):

# First, unzip the tarball (see section on tar, below)
# Next, move into unzipped directory: cd software_directory

# Always read README first if it is provided, in case there are any modifications to the procedure outlined below: cat README

# Automatically check for appropriate configurations and generate a MAKE file in the directory:
./configure

# Compile software. May require sudo: make # Move files into their appropriate locations. May also require sudo: make install

# Clean up files in directory, in case make command fails, or just to remove unnecessary cruft: make clean

***** Ubuntu/Debian Software repositories:

# Check distro repositories for software updates: sudo apt-get update

# Download and install updates (update first): sudo apt-get upgrade

# Search for package in the repositories: apt-cache search keyword

# Get more detail on one specific package: apt-cache show package_name

# Download and install a package: sudo apt-get install package_name

# View the output of a command in a more convenient format: command | less

**** Working With Files:

# Print a file in terminal: cat file

# Find files matching filename: locate filename

# See the version of a program or the location of the program which appname

# Search through filename for matches to phrase: grep phrase filename

# Search through output of a command for phrase: command | grep phrase

**** Working With Processes:

# List all running processes: ps -e

# Standard system monitor showing a more extensive view of all processes and system resources: top # Like top, but with a better, cleaner interface: htop # Stop a process from using all system resources and lagging computer: renice process_name

# Kill misbehaving process (use sparingly, last resort, try 'renice' command first): pkill process name

# Start a process in the background command &

# Start a process in the background and have it keep running after you log off nohup command &

**** Compression and Encryption:

# Make a simple compressed backup of files or directories: tar -cvzf backup_output.tgz target_files_or_directories

# Open a compressed .tgz or .tar.gz file: tar -xvf target.tgz

# Encrypt a file: gpg -o outputfilename.gpg -c target_file

# Decrypt a file: gpg -o outputfilename -d target.gpg

# Zip and encrypt a directory simultaneously: gpg-zip -o encrypted_filename.tgz.gpg -c -s file_to_be_encrypted

*** The Bash shell:
**** File Name expansions:
# Current user's home directory:
~/

# Current directory:
./

# Parent directory:
../

# Or even (Two parent directories down):
../../

# All files in target directory. (Be very careful.):
/*

**** Output Redirects:

# Redirect output of one command into the input of another with a pipe: command_1 | command_2

# Or even:

command_1 | command_2 | command_3

# Redirect output to a file: command > file

# Or:

file > file

# Or even, to redirect in a different direction: file < file

# Append output rather than writing over the target file:

file_or_command >> file

# Works like |, but it writes output to both target and terminal: tee target

# Redirect standard output and error to /dev/null, where it is deleted. command > /dev/null 2>&1

**** Controlling Execution:
# Wait until command 1 is finished to execute command 2 command_1 ; command_2

# Or even: command_1 ; command_2 ; command_3

# && acts like ; but only executes command_2 if command_1 indicates that it succeeded without error by returning 0. command_1 && command_2

# || acts like && but only executes command_2 if command_1 indicates an error by returning 1. command_1 || command_2

**** Bash Wildcards:
# Zero or more characters:
*

# Matches "phrase" and any number of trailing characters: phrase* # Matches any incidences of "phrase" with any trailing or leading chars:
*phrase*

# Matches any one char:
?

# Matches any of the characters listed inside brackets:
[chars]

# Matches a range of chars between a-z:
[a-z]

** Advanced:
*** Command Line Utilities, Continued:
**** Networking:

# Configure network interfaces: ifconfig # Configure wireless network interfaces: iwconfig # Connect to a remote server. ssh username@ip_address

# Forward X from target to current machine (Get a remote desktop. Somewhat obscure, but very useful): ssh -X username@ip_address

# Copy files/directory over the network from one machine to another recursively: scp -r source_filename:username@ip_address target_filename:target_username@target_ip_address

# Copy only changes between files or directories (super efficient way to sync directories, works either locally or with remote servers using username@ip_address:optionalport, just like ssh): rsync source target

# Check to see if target is online and responding ping ip_address

# View network route to target: traceroute6 ip_address

# Network Monitor netstat # View firewall rules iptables -L

# Scan this machine(localhost) to check for open ports: nmap localhost

***** wget:

# download a file over http: wget http://example.com/folder/file

# complete a partially downloaded file: wget -c http://example.com/folder/file

# start download in background: wget -b wget -c http://example.com/folder/file

# download a file from ftp server: wget --ftp-user=USER --ftp-password=PASS ftp://example.com/folder/file

***** netcat:

# Listen for input from network on recieving_port, dump it to a file (insecure, but handy): netcat -l recieving_port > file_copied

# Pipe the output of a command to a target ip and port over the network: command | netcat -w number_of_seconds_before_timeout target_ip target_port

# Use tar to compress and output a file as a stream, pipe it to a target ip and port over the network: sudo tar -czf - filename | netcat -w number_of_seconds_before_timeout target_ip target_port

**** Users and Groups:
# Change owner of a file or directory: chown user_name:group_name directory_name

# Change privileges over file or directory (see man page for details.) chmod # Create a new user: adduser # Change user privileges (be very careful with this one): usermod # Delete user deluser # Print groups: groups # Create a new group: groupadd # Change group privileges: groupmod # Delete group: delgroup # Temporarily become a different user: su username

# Print usernames of logged in users: users # Write one line to another user from your terminal: talk # Interactive talk program to talk to other users from terminal (must be installed from repositories.): ytalk **** Working With Files, Continued:
# View what processes are using what files: lsof # View the differences between two files: diff file_1 file_2

# Output the top number_of_lines of file: head -n number_of_lines file

# Like head, but it outputs the last -n lines: tail -n number_of_lines file

# Checksum a file: md5sum file

# Checksum every file in a directory (install this one from repositories.): md5deep directory

# Checksum a file (better algorithm with no hash collisions): sha1sum # Same operation as md5deep, but using sha1: sha1deep # Call command every few number_of_seconds, and highlight difference in output: watch -d -n number_of_seconds command

# Execute command, print how long it took: time command

# View files in directory from largest to smallest: du -a directory | sort -n -r | less

# remove spaces from filenames in current directory: rename -n 's/[\s]/''/g' *

# change capitals to lowercase in filenames in current directory: rename 'y/A-Z/a-z/' *

***** Environment and Hardware:
# print motherboard information dmidecode # Print full date and time: date # Print the hostname of this machine: echo $HOSTNAME

# Print information about current linux distro: lsb_release -a

# Or even:

more /etc/issue

# Print linux kernel version: uname -a

# Print information about kernel modules: lsmod # Configure kernel modules (never do this ;p ): modprobe # View Installed packages: dpkg --get-selections

# Print environment variables: printenv # List hardware connected via PCI ports: lspci # List hardware connected via USB ports: lsusb # Print hardware info stored in BIOS: sudo dmidecode

# Dump captured data off of wireless card: dumpcap # Dump info about keyboard drivers: dumpkeys ***** Ubuntu System Administration, Advanced (Continued):

# Add a Personal Package Archive from Ubuntu Launchpad: add-apt-repository # Install a .deb file from command line: sudo dpkg -i package.deb

**** Python:

# Update pip (Python package manager): pip install -U pip

# search pip repos for a library: pip search library_name

# create a virtual python environment to allow install of many different versions of the same Python modules: virtualenv dirname --no-site-packages

# connect to a virtual python environment source dirname/bin/activate

# disconnect from a virtual python environment: deactivate # install package into virtual python environment from outside: pip install packagename==version_number -E dirname

# export python virtual environment into a shareable format: pip freeze -E dirname > requirements.txt

# import python virtual environment from a requirements.txt file: pip install -E dirname -r requirements.txt

**** git (all commands must be performed in the same directory as .git folder):

# Start a new git project: git init

git config user.name "user_name"

git config user.email "email"

# Make a copy of a git (target can be specified either locally or remotely, via any number of protocols): git clone target

# Commit changes to a git: git commit -m "message"

# Get info on current repository: git status

# Show change log for current repository: git log

# Update git directory from another repository: git pull [target]

# Push branch to other repository: git push [target]

# Create a new branch: git branch [branchname]

# Switch to target branch: git checkout [branchname]

# Delete a branch: git branch -d [branchname]

# Merge two branches: git merge [branchname] [branchname]

# Show all branches of a project: git branch

*** Virtualization:

#clone a virtual machine (this works, it's been tested): vboxmanage clonehd virtual_machine_name.vdi --format VDI ~/target_virtual_machine_name.vdi

#mount a shared virtual folder:
#you need to make sure you have the right kernel modules. You can do this with modprobe, but this package works instead in a ubuntu-specific way.

sudo apt-get install virtualbox-ose-guest-utils

sudo mount -t vboxsf name_of_shared_folder_specified_in_Virtualbox path_of_mountpoint

*** mysql:

# Get help: help # Show databases: show databases;

# Choose a database to use: use database_name_here;

# Show database schema: show tables;

# Delete database:
DROP DATABASE databasename;

# New database:
CREATE DATABASE databasename;

# Create a new user:
CREATE USER username@localhost IDENTIFIED BY 'password';

# Show users: select * from mysql.user;

# Delete a user: delete from mysql.user WHERE User='user_name';

# Give user access to all tables (make them root). the "%" means that they can sign in remotely, from any machine, not just localhost.: grant all privileges on *.* to someusr@"%" identified by 'password';

# give certain privileges to a user on a certain database: grant select,insert,update,delete,create,drop on somedb.* to someusr@"%" identified by 'password';

# Tell mysql to use new user priv policies: flush privileges;

# change user password: use mysql;

update user set password='password'('newpassword') where User='user_name';

# mysql command line args:
# export text file with commands to rebuild all mysql tables: mysqldump databasename > dumpfilename.txt

# restore from a dump: mysql -u username -p < dumpfilename.txt

# dump entire database: mysqldump -u username -p --opt databasename > dumpfile.sql

# restore from entire database dump: mysql -u username -p --database=databasename < dumpfile.sql