LINUX Cheat Sheet

1 – SYSTEM INFORMATION

uname -a# Display Linux system informationuname -r# Display kernel release informationcat /etc/redhat-release# Show which version of Red Hat installeduptime# Show how long the system has been running + loadhostname# Show system host namehostname -I# Display all local IP addresses of the hostlast reboot# Show system reboot historydate# Show the current date and timecal# Show this month’s calendarw# Display who is onlinewhoami# Who you are logged in as

2 – HARDWARE INFORMATION

dmesg# Display messages in kernel ring buffercat /proc/cpuinfo# Display CPU informationcat /proc/meminfo# Display memory informationfree -h# Display free and used memory ( ​-h​ for human readable,-m​ for MB, ​-g​ for GB.)lspci -tv# Display PCI deviceslsusb -tv# Display USB devicesdmidecode# Display DMI/SMBIOS (hardware info) from the BIOShdparm -i /dev/sda# Show info about disk sdahdparm -tT /dev/sda# Perform a read speed test on disk sdabadblocks -s /dev/sda# Test for unreadable blocks on disk sdaLINUX COMMAND LINE CHEAT SHEET ​https://www.LinuxTrainingAcademy.com2

3 – PERFORMANCE MONITORING AND STATISTICS

top# Display and manage the top processeshtop# Interactive process viewer (top alternative)mpstat 1# Display processor related statisticsvmstat 1# Display virtual memory statisticsiostat 1# Display I/O statisticstail -100 /var/log/messages# Display the last 100 syslog messages (Use/var/log/syslog​ for Debian based systems.)tcpdump -i eth0# Capture and display all packets on interface eth0tcpdump -i eth0 ‘port 80’# Monitor all traffic on port 80 ( HTTP )lsof# List all open files on the systemlsof -u user# List files opened by ​userfree -h# Display free and used memory ( -h for humanreadable, -m for MB, -g for GB.)watch df -h# Execute “df -h”, showing periodic updates

4 – USER INFORMATION AND MANAGEMENTid# Display the user and group ids of yourcurrent user.last# Display the last users who have logged ontothe system.who# Show who is logged into the system.w# Show who is logged in and what they aredoing.groupadd test# Create a group named “test”.useradd -c “John Smith” -m john# Create an account named john, with acomment of “John Smith” and create the user’shome directory.userdel john# Delete the john account.usermod -aG sales john# Add the john account to the sales groupLINUX COMMAND LINE CHEAT SHEET ​https://www.LinuxTrainingAcademy.com3

5 – FILE AND DIRECTORY COMMANDSls -al# List all files in a long listing (detailed) formatpwd# Display the present working directorymkdir directory# Create a directoryrm file# Remove (delete) filerm -r directory# Remove the directory and its contentsrecursivelyrm -f file# Force removal of file without prompting forconfirmationrm -rf directory# Forcefully remove directory recursivelycp file1 file2# Copy file1 to file2cp -r source_directory destination# Copy ​source_directory​ recursively todestination​. If destination exists, copysource_directory​ into ​destination​,otherwise create ​destination​ with thecontents of ​source_directory​.mv file1 file2# Rename or move ​file1​ to ​file2​. If file2 isan existing directory, move file1 into directoryfile2ln -s /path/to/file linkname# Create symbolic link to ​linknametouch file# Create an empty file or update the accessand modification times of file.cat file# View the contents of ​fileless file# Browse through a text filehead file# Display the first 10 lines of ​filetail file# Display the last 10 lines of ​filetail -f file# Display the last 10 lines of ​file​ and “follow”the file as it grows.LINUX COMMAND LINE CHEAT SHEET ​https://www.LinuxTrainingAcademy.com4

6 – PROCESS MANAGEMENT

ps# Display your currently running processesps -ef# Display all the currently running processes on thesystem.ps -ef | grep processname# Display process information for ​processnametop# Display and manage the top processeshtop# Interactive process viewer (top alternative)kill pid# Kill process with process ID of p​idkillall processname# Kill all processes named ​processnameprogram &# Start ​program​ in the backgroundbg# Display stopped or background jobsfg# Brings the most recent background job toforegroundfg n# Brings job ​n​ to the foreground

7 – FILE PERMISSIONS

PERMISSION EXAMPLE U G W rwx rwx rwx chmod 777 filename # Use sparingly! rwx rwx r-x chmod 775 filename rwx r-x r-x chmod 755 filename rw- rw- r– chmod 664 filename rw- r– r– chmod 644 filenameLINUX COMMAND LINE CHEAT SHEET ​https://www.LinuxTrainingAcademy.com5

LEGEND U = User G = Group W = World r = Read w = write x = execute – = no access

8 – NETWORKING

ip a# Display all network interfaces and IP addressip addr show dev eth0# Display eth0 address and detailsethtool eth0# Query or control network driver and hardware settingsping host# Send ICMP echo request to ​hostwhois domain# Display whois information for ​domaindig domain# Display DNS information for ​domaindig -x IP_ADDRESS# Reverse lookup of ​IP_ADDRESShost domain# Display DNS IP address for ​domainhostname -i# Display the network address of the host name.hostname -I# Display all local IP addresses of the host.wget http://domain.com/file# Download ​http://domain.com/filenetstat -nutlp# Display listening tcp and udp ports and correspondingprograms

9 – ARCHIVES (TAR FILES)

tar cf archive.tar directory# Create tar named ​archive.tar​ containingdirectory​.tar xf archive.tar# Extract the contents from ​archive.tar​.tar czf archive.tar.gz directory# Create a gzip compressed tar file namearchive.tar.gz​.LINUX COMMAND LINE CHEAT SHEET ​https://www.LinuxTrainingAcademy.com6

tar xzf archive.tar.gz# Extract a gzip compressed tar file.tar cjf archive.tar.bz2 directory# Create a tar file with bzip2 compressiontar xjf archive.tar.bz2# Extract a bzip2 compressed tar file.

10 – INSTALLING PACKAGES

yum search keyword# Search for a package by ​keyword​.yum install package# Install ​package​.yum info package# Display description and summary informationabout ​package​.rpm -i package.rpm# Install package from local file namedpackage.rpmyum remove package# Remove/uninstall ​package​.tar zxvf sourcecode.tar.gzcd sourcecode./configuremakemake install# Install software from source code.

11 – SEARCH

grep pattern file# Search for ​pattern​ in ​filegrep -r pattern directory# Search recursively for ​pattern​ in ​directorylocate name# Find files and directories by namefind /home/john -name ‘prefix*’# Find files in ​/home/john​ that start with “prefix”.find /home -size +100M# Find files larger than 100MB in /home

12 – SSH LOGINS

ssh host# Connect to ​host​ as your local username.ssh user@host# Connect to ​host​ as ​userssh -p port user@host# Connect to ​host​ using ​portLINUX COMMAND LINE CHEAT SHEET ​https://www.LinuxTrainingAcademy.com7

13 – FILE TRANSFERS

scp file.txt server:/tmp# Secure copy ​file.txt ​to the /tmp folder onserverscp server:/var/www/*.html /tmp# Copy ​*.html​ files from ​server​ to the local/tmp folder.scp -r server:/var/www /tmp# Copy all files and directories recursively fromserver​ to the current system’s /tmp folder.rsync -a /home /backups/# Synchronize ​/home​ to​ /backups/homersync -avz /home server:/backups/# Synchronize files/directories between the localand remote system with compression enabled

14 – DISK USAGE

df -h# Show free and used space on mounted filesystemsdf -i# Show free and used inodes on mounted filesystemsfdisk -l# Display disks partitions sizes and typesdu -ah# Display disk usage for all files and directories inhuman readable formatdu -sh# Display total disk usage off the current directory

15 – DIRECTORY NAVIGATION

cd ..# To go up one level of the directory tree. (Change intothe parent directory.)cd# Go to the $HOME directorycd /etc# Change to the /etc directoryLINUX COMMAND LINE CHEAT SHEET ​https://www.LinuxTrainingAcademy.com8