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Linux Cheat Sheet

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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 command1 indicates that it succeeded without error by returning 0.
command_1 && command_2
  • || acts like && but only executes command2 if command1 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.1620855846.txt.gz · Last modified: 2021/05/12 21:44 by bpienig
 
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