# add a new user interactively
sudo adduser '<NEW_USERNAME>'
# add a new service account interactively
sudo adduser --disabled-password '<NEW_USERNAME>'
# add a new service account non-interactively
sudo adduser --disabled-password --gecos "" '<NEW_USERNAME>'# perform a GET request, print headers to stdout
curl -s -L -D - -o /dev/null '<URL>'# Write ISO to a USB. Be sure to unmount any mounted partitions before attempting.
sudo dd bs=4M if='<PATH_TO_ISO>' of='<PATH_TO_USB_BLOCK_DEVICE>' && sync# recursively compare two directories and list differences
diff -rq directory1/ directory2/
# diff output of 2 commands
diff <(command1 arg1 arg2) <(command2 arg1 arg2)# get everything
dig example.com
# return MX records only
dig example.com MX
# use a specific dns server (e.g. cloudflare)
dig @1.1.1.1 A 'example.com'eyeD3 -A '<ALBUM_NAME>' -b '<ALBUM_NAME>' --add-image '<PATH_TO_FILE>':FRONT_COVER '<INPUT_MP3>'# delete all GPS and XMP metadata from a media file
exiftool -gps:all= -xmp-exif:all= '<FILES_TO_PROCESS>'# find all files in a directory older than 10 days and delete them
find '<PATH_TO_DIRECTORY>' -mtime +10 -name '*.pdf' -type f -delete
# Recursively delete music metadata files
find . -name '*.nfo' -type f -delete
find . -name '*.m3u' -type f -delete
find . -name '*.m3u8' -type f -delete
# remove a file from git index but don't delete the local copy.
git rm --cached '<PATH_TO_FILE>'
# squash the last 3 commits
git reset --soft HEAD~3 && git commit -m '<NEW_MESSAGE>' && git push -f
# delete the most recent commit and rollback changes to the previous commit
git reset --hard HEAD~1
# add upstream to a GitHub fork
git remote add upstream 'https://github.com/<ORIGINAL_OWNER>/<ORIGINAL_REPOSITORY>.git'
# sync a GitHub fork with master. Be sure to have added 'upstream' as a remote
git fetch upstream && git checkout master && git merge upstream/master
# show content of last stash
git stash show -p
# delete your local changes and replace with what is currently on master
git fetch --all && git reset --hard origin/master
# don't use your system keychain for this repository
git config --local credential.helper ""
# Have git prompt for your new password next push
git config --global --unset user.password
# sync a branch with master
git checkout master && git pull && git checkout '<BRANCH_TO_SYNC>' && git merge master
# cherry pick a commit
git cherry-pick -x '<COMMIT_SHA>'
# clear saved git passwords in macOS keychain, make sure to press enter key after each line.
git credential-osxkeychain erase
host=github.com
protocol=https
# permanently delete all dangling commits
git reflog expire --expire-unreachable=now --all
git gc --prune=now# generate a key
gpg --full-generate-key
# list keys and show short IDs (used by gradle)
gpg --list-keys --keyid-format SHORT
# list keys for which I have both the public and private keys
gpg --list-secret-keys --keyid-format LONG
# Print GPG public key in ASCII armor format
gpg --armor --export "<GPG_KEY_ID>"
# Publish a public key (using Ubuntu's keyservers)
gpg --keyserver keyserver.ubuntu.com --send-keys "<GPG_KEY_ID>"
# Force gpg to output a secring.gpg file in the current directory
gpg --export-secret-keys -o secring.gpg# recursive grep for text in files
grep -rnw '<ROOT_DIRECTORY_TO_SEARCH>' -e '<PATTERN>'# list current user's groups
groups
# list another user's groups
groups '<USERNAME>'
# Add existing user to new group
sudo usermod -a -G '<GROUP_TO_ADD>' '<USERNAME>'
# list users on a system
compgen -u# Remove a white background from an image
convert '<INPUT_FILE>' -fuzz 20% -transparent white out.png
# Make a GIF from JPG files in a directory
convert -dispose none -loop 0 -delay 100 *.JPG -resize 20% out.gif
# Create a favicon from a square png
convert '<SOURCE_PNG_FILE>' -background transparent -define icon:auto-resize=16,24,32,48,64,72,96,128,256 favicon.ico
# Convert a pdf to png (high resolution)
convert -density 288 '<INPUT_PDF>' '<OUTPUT_PNG>'
# Convert a svg to png with height 1000, high density, and alpha transparency
convert -resize x1000 -density 1200 -background none '<INPUT_SVG>' 'OUTPUT_PNG'
# get detailed information about an image
magick identify -verbose '<PATH_TO_IMG>'# Start iperf3 server
iperf3 -s
# connect to server with iperf3 client
iperf3 -c '<SERVER_IP>'# Quickly (-n) list all open sockets by port (-P) on local device
lsof -Pn -i4# create symlink. Omit trailing slashes
ln -s '<DIRECTORY_TO_LINK_TO>' '<NEW_SYM_LINK_NAME>'# restart an nginx service
sudo nginx -t && sudo systemctl restart nginx# Scan all ports, no ping (-Pn), no DNS resolution (-n, helps reduce scan time)
nmap -n -Pn -p 0-65535 127.0.0.1
# Scan specific ports, no ping
nmap -Pn -p 80,443,555 127.0.0.1
# Scan all ports, be aggressive, probe for OS/app versions
nmap -p 1-65535 -T4 -A -v 127.0.0.1
# Host discovery on a CIDR range
nmap -sP 10.0.1.0/24-A- enables OS/version detection, script scanning, and traceroute--allports- enables scanning on 9100, a printer port. Caveat: some printers print anything sent to this port.-T4/-T5- use an aggressive/insane timing template
# check if a port is open, close connection immediately
nc -vz '<SERVER_IP>' '<PORT>'# Initalize a dev php server at localhost:8080 rooted at ./public_html
php -S localhost:8080 -t public_html/# get process name if you have its pid
ps -p '<PID>' -o comm=
# get detailed information about process with PID
ps -Flw -p '<THE_PID>'# Recursively delete duplicate files in a directory
rdfind -deleteduplicates true '<PATH_TO_DIRECTORY>'# archive, show progress, delete files on dest. Note trailing slash on SOURCE_FOLDER
rsync -avh --progress --delete "<SOURCE_FOLDER>/" "<DEST_FOLDER>"
# archive, use ssh to copy to dest on server
rsync -avh "<SOURCE_FOLDER>/" "[email protected]:<DEST_FOLDER>"-a stands for "archive mode", implies:
-r: recursive-l: copy symlinks as symlinks-p: preserve permissions-t: preserve times-g: preserve group-o: preserve owner (super-user only)-D: preserve device files and special files
other interesting args:
-v- verbose-h- human readable-P- show progress bar and keep partially copied files-n- dry run--delete- delete files on dest which are not in source-u- skip files that are newer on destination
# compare against entire process name (why isn't this the default?!)
pgrep -f '<PATTERN>'# Extract images from pdf
pdfimages -all '<INPUT_PDF>' '<OUTPUT_DIR>/<IMAGE_PREFIX_TO_USE>'# Start a new screen
screen '<PROGRAM_TO_RUN>' '<PROGRAM_ARGUMENTS>'- Enter command mode, use shortcut
Control+awhile running a screen. - To detach from the screen, press
d. - To kill the current screen, press
k. - To get documentation, press
?.
# List screens from bash
screen -ls
# Reattach a screen
screen -r '<PID>' # pid comes from doing screen -ls# create or change password of samba user
smbpasswd -a '<USERNAME_TO_CREATE_OR_CHANGE>'
# enable the account of an existing samba user
sudo smbpasswd -e '<USERNAME_TO_CREATE_OR_CHANGE>'
# create a system user for use with samba
sudo adduser --no-create-home --shell /usr/sbin/nologin --disabled-password --disabled-login --ingroup sambashare '<USERNAME>'
# Various ways to get status/information about smbd:
smbstatus
pdbedit -L -v
net usershare info --long
smbtree# Generate a spectrogram for an audio file
sox '<INPUT_FILE>' -n spectrogram -o out.png# run a local script on a server
ssh 'username@hostname' 'bash -s' < '<LOCAL_PATH_TO_SCRIPT>'
# List supported key types on a client
ssh -Q key
# Probe a server about its supported ssh algorithims
nmap --script ssh2-enum-algos -sV -Pn -p 22 '<HOSTNAME_OR_IP>'
# Get info about an existing ssh key (either pub or priv key)
ssh-keygen -l -f '<PATH_TO_FILE>'
# Remove an entry from known_hosts
ssh-keygen -R '<HOSTNAME_OR_IP>'
# Generate a new ed25519 priv/pub pair (best practice)
ssh-keygen -t ed25519 -C '<DESCRIPTION>'
# Generate a new rsa priv/pub pair (legacy systems)
ssh-keygen -t rsa -b 4096 -C '<DESCRIPTION>'# get status of a service
systemctl status '<SERVICE_NAME>'
# enable service at boot
systemctl enable '<SERVICE_NAME>'
# list all known services
systemctl list-units --all
# list all known unit files
systemctl list-unit-files
# display a unit file
systemctl cat '<SERVICE_NAME>'
# display service's dependencies
systemctl list-dependencies '<SERVICE_NAME>'
# mark a service as unstartable by nobody
systemctl mask '<SERVICE_NAME>'
# unmask a service and return it to its previous state
systemctl unmask '<SERVICE_NAME>'
# reload unit files after editing them
systemctl daemon-reload# Extract .tar.gz
tar -xvzf '<PATH_TO_TAR_FILE>'
# Create .tar.xz, based out of the specified dir
tar -cJf '<NAME_OF_FILE>.tar.xz' -C 'DIR_TO_USE_AS_ROOT_OF_TAR' .
# Create .tar.xz, use as many threads as possible
XZ_OPT='-T0' tar -cJf '<NAME_OF_FILE>.tar.xz' .# see all registered firewall profiles
ufw app list
# allow a profile/rule
ufw allow '<PROFILE/PORT>'
# show status
ufw status
# show status with rule priority
ufw status numbered
# delete a rule with id obtained from 'ufw status numbered'
ufw delete '<RULE_ID>'
# start firewall
ufw enable# download all media files on a page
wget -nd -r -l 1 -H -A png,gif,jpg,svg,jpeg,webm -e robots=off '<WEBSITE_URL>'
# recursively download the contents of a website
wget -e robots=off -m -k -np -w 5 '<URL>'
# download contents of an open directory (not recursive)
wget --no-directories --no-parent -r -l 1 -H '<URL>'# get whois data for host
whois example.com# view binary files
xxd -b '<THE_FILE>' | less# rip embedded vimeo
yt-dlp '<LINK_TO_VIDEO>' --referer '<LINK_TO_PAGE_VIDEO_IS_EMBEDED_ON>'