Linux Commands Cheat Sheet

Did you know that there are literally hundreds of Linux commands? Even on a bare-bones Linux server install there are easily over 1,000 different commands. The interesting thing is that most people only need to use a very small subset of those commands. Below you’ll find a Linux “cheat sheet” that breaks down some of the most commonly used commands by category. To get your own PDF and printable copy.

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1 – SYSTEM INFORMATION

• Display Linux system information

  uname -a

• Display kernel release information

  uname -r

• Show operating system information such as distribution name and version

  cat /etc/os-release

• Show how long the system has been running + load

  uptime

• Show system host name

  hostname

• Display all local IP addresses of the host.

  hostname -I

• Show system reboot history

  last reboot

• Show the current date and time

  date

• Show this month’s calendar

  cal

• Display who is online

  w

• Who you are logged in as

  whoami

2 – HARDWARE INFORMATION

• Display messages in kernel ring buffer

  dmesg

• Display CPU information

  cat /proc/cpuinfo

• Display memory information

  cat /proc/meminfo

• Display free and used memory ( -h for human readable, -m for MB, -g for GB.)

  free -h

• Display PCI devices

  lspci -tv

• Display USB devices

  lsusb -tv

• Display DMI/SMBIOS (hardware info) from the BIOS

  dmidecode

• Show info about disk sda

  hdparm -i /dev/sda

• Perform a read speed test on disk sda

  hdparm -tT /dev/sda

• Test for unreadable blocks on disk sda

  badblocks -s /dev/sda

3 – PERFORMANCE MONITORING AND STATISTICS

• Display and manage the top processes

  top

• Interactive process viewer (top alternative)

  htop

• Display processor related statistics

  mpstat 1

• Display virtual memory statistics

  vmstat 1

• Display I/O statistics

  iostat 1

• Display the last 100 syslog messages (Use /var/log/syslog for Debian based systems.)

  tail -100 /var/log/messages

• Capture and display all packets on interface eth0

  tcpdump -i eth0

• Monitor all traffic on port 80 ( HTTP )

  tcpdump -i eth0 ‘port 80’

• List all open files on the system

  lsof

• List files opened by user

  lsof -u user

• Display free and used memory ( -h for human readable, -m for MB, -g for GB.)

  free -h

• Execute “df -h”, showing periodic updates

  watch df -h

4 – USER INFORMATION AND MANAGEMENT

• Display the user and group ids of your current user.

  id

• Display the last users who have logged onto the system.

  last

• Show who is logged into the system.

  who

• Show who is logged in and what they are doing.

  w

• Create a group named “test”.

  groupadd test

• Create an account named john, with a comment of “John Smith” and create the user’s home directory.

  useradd -c “John Smith” -m john

• Delete the john account.

  userdel john

• Add the john account to the sales group

  usermod -aG sales john

5 – FILE AND DIRECTORY COMMANDS

• List all files in a long listing (detailed) format

  ls -al

• Display the present working directory

  pwd

• Create a directory

  mkdir directory

• Remove (delete) file

  rm file

• Remove the directory and its contents recursively

  rm -r directory

• Force removal of file without prompting for confirmation

  rm -f file

• Forcefully remove directory recursively

  rm -rf directory

• Copy file1 to file2

  cp file1 file2

• Copy source_directory recursively to destination. If destination exists, copy source_directory into destination, otherwise create destination with the contents of source_directory.

  cp -r source_directory destination

• Rename or move file1 to file2. If file2 is an existing directory, move file1 into directory file2

  mv file1 file2

• Create symbolic link to linkname

  ln -s /path/to/file linkname

• Create an empty file or update the access and modification times of file.

  touch file

• View the contents of file

  cat file

• Browse through a text file

  less file

• Display the first 10 lines of file

  head file

• Display the last 10 lines of file

  tail file

• Display the last 10 lines of file and “follow” the file as it grows.

  tail -f file

6 – PROCESS MANAGEMENT

• Display your currently running processes

  ps

• Display all the currently running processes on the system.

  ps -ef

• Display process information for processname

  ps -ef | grep processname

• Display and manage the top processes

  top

• Interactive process viewer (top alternative)

  htop

• Kill process with process ID of pid

  kill pid

• Kill all processes named processname

  killall processname

• Start program in the background

  program &

• Display stopped or background jobs

  bg

• Brings the most recent background job to foreground

  fg

• Brings job n to the foreground

  fg n

7 – FILE PERMISSIONS

      U   G   W
        rwx rwx rwx     chmod 777 filename
        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 filename

        LEGEND
        U = User
        G = Group
        W = World

        r = Read
        w = write
        x = execute
        - = no access

8 – NETWORKING

• Display all network interfaces and IP address

  ip a

• Display eth0 address and details

  ip addr show dev eth0

• Query or control network driver and hardware settings

  ethtool eth0

• Send ICMP echo request to host

  ping host

• Display whois information for domain

  whois domain

• Display DNS information for domain

  dig domain

• Reverse lookup of IP_ADDRESS

  dig -x IP_ADDRESS

• Display DNS IP address for domain

  host domain

• Display the network address of the host name.

  hostname -i

• Display all local IP addresses of the host.

  hostname -I

• Download http://example.com/file

  wget http://example.com/file

• Display listening tcp and udp ports and corresponding programs

  netstat -nutlp

9 – ARCHIVES (TAR FILES)

• Create tar named archive.tar containing directory.

  tar cf archive.tar directory

• Extract the contents from archive.tar.

  tar xf archive.tar

• Create a gzip compressed tar file name archive.tar.gz.

  tar czf archive.tar.gz directory

• Extract a gzip compressed tar file.

  tar xzf archive.tar.gz

• Create a tar file with bzip2 compression

  tar cjf archive.tar.bz2 directory

• Extract a bzip2 compressed tar file.

  tar xjf archive.tar.bz2

10 – INSTALLING PACKAGES

• Search for a package by keyword.

  yum search keyword

• Install package.

  yum install package

• Display description and summary information about package.

  yum info package

• Install package from local file named package.rpm

  rpm -i package.rpm

• Remove/uninstall package.

  yum remove package

• Install software from source code.

  tar zxvf sourcecode.tar.gz cd sourcecode ./configure make make install

11 – SEARCH

• Search for pattern in file

  grep pattern file

• Search recursively for pattern in directory

  grep -r pattern directory

• Find files and directories by name

  locate name

• Find files in /home/john that start with “prefix”.

  find /home/john -name ‘prefix*’

• Find files larger than 100MB in /home

  find /home -size +100M

12 – SSH LOGINS

• Connect to host as your local username.

  ssh host

• Connect to host as user

  ssh user@host

• Connect to host using port

  ssh -p port user@host

13 – FILE TRANSFERS

• Secure copy file.txt to the /tmp folder on server

  scp file.txt server:/tmp

• Copy *.html files from server to the local /tmp folder.

  scp server:/var/www/*.html /tmp

• Copy all files and directories recursively from server to the current system’s /tmp folder.

  scp -r server:/var/www /tmp

• Synchronize /home to /backups/home

  rsync -a /home /backups/

• Synchronize files/directories between the local and remote system with compression enabled

  rsync -avz /home server:/backups/

14 – DISK USAGE

• Show free and used space on mounted filesystems

  df -h

• Show free and used inodes on mounted filesystems

  df -i

• Display disks partitions sizes and types

  fdisk -l

• Display disk usage for all files and directories in human readable format

  du -ah

• Display total disk usage off the current directory

  du -sh

15 – DIRECTORY NAVIGATION

• To go up one level of the directory tree. (Change into the parent directory.)

  cd ..

• Go to the $HOME directory

  cd

• Change to the /etc directory

  cd /etc

16 – SECURITY

• Change the current user’s password.

  passwd

• Switch to the root account with root’s environment. (Login shell.)

  sudo -i

• Execute your current shell as root. (Non-login shell.)

  sudo -s

• List sudo privileges for the current user.

  sudo -l

• Edit the sudoers configuration file.

  visudo

• Display the current SELinux mode.

  getenforce

• Display SELinux details such as the current SELinux mode, the configured mode, and the loaded policy.

  sestatus

• Change the current SELinux mode to Permissive. (Does not survive a reboot.)

  setenforce 0

• Change the current SELinux mode to Enforcing. (Does not survive a reboot.)

  setenforce 1

• Set the SELinux mode to enforcing on boot by using this setting in the /etc/selinux/config file.

  SELINUX=enforcing

• Set the SELinux mode to permissive on boot by using this setting in the /etc/selinux/config file.

  SELINUX=permissive

• Set the SELinux mode to disabled on boot by using this setting in the /etc/selinux/config file.

  SELINUX=disabled

17 – LOGGING AND AUDITING

• Display messages in kernel ring buffer.

  dmesg

• Display logs stored in the systemd journal.

  journalctl

• Display logs for a specific unit (service).

  journalctl -u servicename