Linux Cheat Sheet / Advanced Command Reference

# Perform forward or reverse lookup on string

host string

# Lookup string’s host info from nameserver

dig @nameserver string

# Move all files containing string to /path

find . -type f -exec grep -l string {} \; -exec mv {} /path \;

# Change ownership and group of all files recursively

chown -cR --from=usera:groupa userb:groupb *

# Find total amount of RAM in the system

grep -i memtotal /proc/meminfo

# Display DMI/SMBIOS information

dmidecode -q

# Display CPU information

cat /proc/cpuinfo

# See if a processor supports hardware virtualization

egrep '(vmx|svm)' /proc/cpuinfo

# Display PCI information

lspci -tv

# Display USB information

lsusb -tv

# Display disk information for sda

hdparm -i /dev/sda

# Recursively download entire website

wget -r -np -nH -mkp -e robots=off http://www.domain.com/

# Replace all X's with Y's in all files this directory and below.

find . -type f -print -exec sed -i -e 's|X|Y|g' {} \;

# View special characters in files. Isolate \n\r issues.

od -c

# Fix some DOS file formatting issues. ^V means Control-V

%/\n\n/^V^M/g

# Replace all X's with Y's in all files ending with *.txt

perl -pi -w -e 's/X/Y/g;' *.txt

# Print filename and all lines containing 'string'

find -name '*' | xargs grep 'string'

# Print all file names containing Test String in all subdirectories

grep -Hir "Test String" .

# Recursively copy while preserving permissions

scp -p -r [USER]@[HOST]:file /dir

# Create public & private keys on LOCAL-HOST

ssh-keygen

# Install public key for trusted login on REMOTE-HOST

ssh-copy-id -i ~/.ssh/id_rsa.pub [REMOTE-HOST]

# Jump though host1 to access host2

ssh -J root@host1.domain.com root@host2.domain.com

# Full process list with Child Process Tree

ps -auxf

# List all active network connections and state

netstat -tup

# Show information related to http (port 80) connections

lsof -i :80

# List open files by a particular userid

lsof -u userid

# List active network connections consuming bandwidth

iftop

# Top for Apache web server

apachetop -f logfile

# Find out which patches have been applied to a package

rpm -q --changelog PACKAGE-NAME

# Monitor IP Traffic

iptraf

# Like top, but with an h

htop

# My Traceroute - An improved traceroute

mtr

# Tail multiple files at the same time

multitail

# A http/web stress test utility

siege

# Scan local network for windows shares

smbtree

# List all open files and show IP addresses with process IDs

smbstatus

clamscan -ir --scan-mail=no --exclude-dir="mail" .

netstat -an | grep :80 | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr

netstat -anp | grep 'tcp\|udp' | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr

netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr

netstat -ntu | grep -v TIME_WAIT | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr

netstat -n --tcp --udp --numeric-hosts | grep -v 127.0.0.1 | awk '{if (/(tcp|udp)/) { print $5 }}' | sed 's/:.*//' | sort | uniq -c | sort -n | awk '{if ($1 > 20) {print "Count: "$1"\t"$2; }}'

# Isolate Spam Scripts in WHM/CPanel Environment

grep cwd /var/log/exim_mainlog | grep -v /var/spool | awk -F"cwd=" '{print $2}' | awk '{print $1}' | sort | uniq -c | sort -n