Terminal Cheat Sheet
1 – SYSTEM INFORMATION
# Display Linux system information uname -a
Display kernel release information
uname -r
Show which version of Red Hat installed
cat /etc/redhat-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
NOTE: Use 777 sparingly!
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://domain.com/file
wget http://domain.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
ls
Lists all files and directories in the present working directory
ls-R
Lists files in sub-directories as well
ls-a
Lists hidden files as well
ls-al
Lists files and directories with detailed information like permissions,size, owner, etc.
cd or cd ~
Navigate to HOME directory
cd ..
Move one level up
cd
To change to a particular directory
cd /
Move to the root directory
cat > filename
Creates a new file
cat filename
Displays the file content
cat file1 file2 > file3
Joins two files (file1, file2) and stores the output in a new file (file3)
mv file "new file path"
Moves the files to the new location
mv filename new_file_name
Renames the file to a new filename
sudo
Allows regular users to run programs with the security privileges of the superuser or root
rm filename
Deletes a file
man
Gives help information on a command
history
Gives a list of all past commands typed in the current terminal session
clear
Clears the terminal
mkdir directoryname
Creates a new directory in the present working directory or a at the specified path
rmdir
Deletes a directory
mv
Renames a directory
pr -x
Divides the file into x columns
pr -h
Assigns a header to the file
pr -n
Denotes the file with Line Numbers
lp -nc , lpr c
Prints "c” copies of the File
lp-d lp-P
Specifies name of the printer
apt-get
Command used to install and update packages
mail -s 'subject'
Command to send email
-c 'cc-address'
-b 'bcc-address'
'to-address'
mail -s "Subject"
Command to send email with attachment
to-address < Filename
Linux File Permissions
File Permission commands
Command
Description
ls-l
to show file type and access permission
r
read permission
w
write permission
x
execute permission
-=
no permission
Chown user
For changing the ownership of a file/directory
Chown user:group filename
change the user as well as group for a file or directory
Environment Variables command
Command
Description
echo $VARIABLE
To display value of a variable
env
Displays all environment variables
VARIABLE_NAME= variable_value
Create a new variable
Unset
Remove a variable
export Variable=value
To set value of an environment variable
User management commands of linux
Command
Description
sudo adduser username
To add a new user
sudo passwd -l 'username'
To change the password of a user
sudo userdel -r 'username'
To remove a newly created user
sudo usermod -a -G GROUPNAME USERNAME
To add a user to a group
sudo deluser USER GROUPNAME
To remove a user from a group
finger
Shows information of all the users logged in
finger username
Gives information of a particular user
Networking command
Command
Description
SSH username@ip-address or hostname
login into a remote Linux machine using SSH
Ping hostname="" or =""
To ping and Analyzing network and host connections
dir
Display files in the current directory of a remote computer
cd "dirname"
change directory to "dirname” on a remote computer
put file
upload ‘file' from local to remote computer
get file
Download ‘file' from remote to local computer
quit
Logout
Process command
Command
Description
bg
To send a process to the background
fg
To run a stopped process in the foreground
top
Details on all Active Processes
ps
Give the status of processes running for a user
ps PID
Gives the status of a particular process
pidof
Gives the Process ID (PID) of a process
kill PID
Kills a process
nice
Starts a process with a given priority
renice
Changes priority of an already running process
df
Gives free hard disk space on your system
free
Gives free RAM on your system
VI Editing Commands
Command
Description
i
Insert at cursor (goes into insert mode)
a
Write after cursor (goes into insert mode)
A
Write at the end of line (goes into insert mode)
ESC
Terminate insert mode
u
Undo last change
U
Undo all changes to the entire line
o
Open a new line (goes into insert mode)
dd
Delete line
3dd
Delete 3 lines
D
Delete contents of line after the cursor
C
Delete contents of a line after the cursor and insert new text. Press ESC key to end insertion.
dw
Delete word
4dw
Delete 4 words
cw
Change word
x
Delete character at the cursor
r
Replace character
R
Overwrite characters from cursor onward
s
Substitute one character under cursor continue to insert
S
Substitute entire line and begin to insert at the beginning of the line
~
Change case of individual character
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