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Linux Cheat Sheet

The contents of this file are released under the GNU General Public License. Feel free to reuse the contents of this work, as long as the resultant works give proper attribution and are made publicly available under the GNU General Public License.

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 command2 if command_1 indicates that it succeeded without error by returning 0.

command_1 && command_2

double pipes || act 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 numberoflines 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 numberofseconds, 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: <file bash>mysql -u username -p –database=databasename < dumpfile.sql

 
 linuxfind.1620856883.txt.gz · Last modified: 2021/05/12 22:01 by bpienig
 
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