uname -a # Display Linux system information
uname -r # Display kernel release information
cat /etc/redhat-release # Show which version of Red Hat installed
uptime # Show how long the system has been running + load
hostname # Show system host name
hostname -I # Display all local IP addresses of the host.
last reboot # Show system reboot history
date # Show the current date and time
cal # Show this month's calendar
w # Display who is online
whoami # Who you are logged in as
!! # Run the last command
history # Reviewing your Previous Bash History
history 5 # Last 5 history
history | grep cd # Filter cd comandsdmesg # Display messages in kernel ring buffer
cat /proc/cpuinfo # Display CPU information
cat /proc/meminfo # Display memory information
free -h # Display free and used memory
lsusb # List USB devices
lspci # List PCI hardware
lshw # List all hardware
dmidecode # Display DMI/SMBIOS (hardware info) from the BIOS
hdparm -i /dev/sda # Show info about disk sda
hdparm -tT /dev/sda # Perform a read speed test on disk sda
badblocks -s /dev/sda # Test for unreadable blocks on disk sdampstat 1 # Display processor related statistics
vmstat 1 # Display virtual memory statistics
iostat 1 # Display I/O statistics
tail -100 /var/log/messages # Display the last 100 syslog messages
tcpdump -i eth0 # Capture and display all packets on interface eth0
tcpdump -i eth0 'port 80' # Monitor all traffic on port 80 ( HTTP )
lsof # List all open files on the system
lsof -u user # List files opened by user
watch df -h # Execute "df -h", showing periodic updatesservice --status-all # List all services
systemctl stop <service-name> # Stop service
systemctl start <service-name> # Start service
systemctl restart <service-name> # Restart service
systemctl status <service-name> # Service status
service <service-name> stop # Stop service
service <service-name> start # Start service
service <service-name> restart # Restart service
service <service-name> status # Service statusid # Display the user and group ids of your current user.
last # Display the last users who have logged onto the system.
who # Show who is logged into the system.
w # Show who is logged in and what they are doing.
groupadd test # Create a group named "test".
useradd -c "John Smith" -m john # Create an account named john, with a comment of "John Smith" and create the user's home directory.
userdel john # Delete the john account.
usermod -aG sales john # Add the john account to the sales groupls -al # List all files in a long listing (detailed) format
pwd # Display the present working directory
mkdir directory # Create a directory
mkdir foo bar # Create multiple directories
mkdir -pv dir/{foo,bar} # Create multiple nested directories
rm file # Remove (delete) file
rm -r directory # Remove the directory and its contents recursively
rm -f file # Force removal of file without prompting for confirmation
rm -rf directory # Forcefully remove directory recursively
cp file1 file2 # Copy file1 to file2
cp -r source_directory destination # Copy source_directory recursively to destination.
mv file1 file2 # Rename or move file1 to file2.
ln -s /path/to/file linkname # Create symbolic link to linkname
touch file # Create an empty file or update the modification times.
touch {foo,bar}.txt # Create multiple files
touch test{1..3} # Create test1, test2 and test3 files
cat file # View the contents of file
less file # Browse through a text file
head file # Display the first 10 lines of file
stat file # List size, created and modified timestamps for a file
tree # List directory and file tree
tree -a # List directory and file tree including hidden
tree -d # List directory tree
wc file # List number of lines words and characters in the file
type wget # Find the binary
which wget # Find the binary
whereis wget # Find the binary, source, and manual page filesps # Display your currently running processes
ps -ef # Display all the currently running processes on the system.
ps -ef | grep processname # Display process information for processname
top # Display and manage the top processes
htop # Interactive process viewer (top alternative)
kill pid # Kill process with process ID of pid
kill -9 pid # Force Kill process
killall processname # Kill all processes named processname
program & # Start program in the background
bg # Display stopped or background jobs
fg # Brings the most recent background job to foreground
fg n # Brings job n to the foreground
| # | Permission | rwx | Binary |
|---|---|---|---|
| 7 | read, write and execute | rwx | 111 |
| 6 | read and write | rw- | 110 |
| 5 | read and execute | r-x | 101 |
| 4 | read only | r-- | 100 |
| 3 | write and execute | -wx | 011 |
| 2 | write only | -w- | 010 |
| 1 | execute only | --x | 001 |
| 0 | none | --- | 000 |
PERMISSION EXAMPLE
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
chmod +100 foo.sh # Add 1 to the user permission
chmod -100 foo.sh # Subtract 1 from the user permission
chmod u+x foo.sh # Give the user execute permission
chmod g+x foo.sh # Give the group execute permission
chmod u-x,g-x foo.sh # Take away the user and group execute permission
chmod u+x,g+x,o+x foo.sh # Give everybody execute permission
chmod a+x foo.sh # Give everybody execute permission
chmod +x foo.sh # Give everybody execute permissionip a # Display all network interfaces and IP address
ip addr show dev eth0 # Display eth0 address and details
ethtool eth0 # Query or control network driver and hardware settings
ping host # Send ICMP echo request to host
whois domain # Display whois information for domain
dig domain # Display DNS information for domain
dig -x IP_ADDRESS # Reverse lookup of IP_ADDRESS
host domain # Display DNS IP address for domain
hostname -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/file
netstat -nutlp # Display listening tcp and udp ports and corresponding programs
netstat -tulpn
netstat -i # List all network interfaces and in/out usage
netstat -l # List all open ports
traceroute example.com # List all servers the network traffic goes through
nmap 0.0.0.0 # Scan for the 1000 most common open ports on localhost
nmap 0.0.0.0 -p1-65535 # Scan for open ports on localhost between 1 and 65535
nmap 192.168.4.3 # Scan for the 1000 most common open ports on a remote IP address
nmap -sP 192.168.1.1/24 # Discover all machines on the network by ping'ing them
host example.com # Show the IPv4 and IPv6 addresses
dig example.com # Show complete DNS informationtar cf archive.tar directory # Create tar named archive.tar containing directory.
tar xf archive.tar # Extract the contents from archive.tar.
tar czf archive.tar.gz directory # Create a gzip compressed tar file name archive.tar.gz.
tar xzf archive.tar.gz # Extract a gzip compressed tar file.
tar cjf archive.tar.bz2 directory # Create a tar file with bzip2 compression
tar xjf archive.tar.bz2 # Extract a bzip2 compressed tar file.yum search keyword # Search for a package by keyword.
yum install package # Install package.
yum info package # Display description and summary information about package.
rpm -i package.rpm # Install package from local file named package.rpm
yum remove package # Remove/uninstall package.
tar zxvf sourcecode.tar.gz # Install software from source code.
cd sourcecode
./configure
make
make installapt-cache search keyword # Search for a package by keyword.
apt-get install package # Install package.
apt-cache show package # Display description and summary information about package.
apt-get remove package # Remove/uninstall package.
dpkg -i package.deb # Install package from local file named package.rpmgrep pattern file # Search for pattern in file
grep -r pattern directory # Search recursively for pattern in directory
locate name # Find files and directories by name
locate f*.txt # Find file starting with 'f'
find /home -name 'prefix*' # Find files in /home/john that start with "prefix".
find /home -size +100M # Find files larger than 100MB in /home
find /path -name foo.txt # Find a file
find /path -iname foo.txt # Find a file with case insensitive search
find /path -name "*.txt" # Find all text files
find /path -name foo.txt -delete # Find a file and delete it
find /path -type f -name foo.txt # Find a file
find /path -type d -name foo # Find a directory
find /path -type l -name foo.txt # Find a symbolic link
find /path -type f -mtime +30 # Find files that haven't been modified in 30 days
find /path -type f -mtime +30 -delete # Delete files that haven't been modified in 30 daysssh host # Connect to host as your local username.
ssh user@host # Connect to host as user
ssh -p port user@host # Connect to host using port
scp file.txt server:/tmp # Secure copy file.txt to the /tmp folder on server
scp 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 from server to the current system's /tmp folder.
rsync -a /home /backups/ # Synchronize /home to /backups/home
rsync -avz /foo username@hostname:/bar # Copy local directory to remote directory
rsync -avz username@hostname:/foo /bar # Copy remote directory to local directorydf -h # Show free and used space on mounted filesystems
df -i # Show free and used inodes on mounted filesystems
fdisk -l # Display disks partitions sizes and types
du -ah # Display disk usage for all files and directories in human readable format
du -sh # Display total disk usage off the current directory
mount -t ext4 # List Specific File Systems
mount /dev/sdb1 /mnt/media # Mount a File System
mount -t iso9660 -o ro /dev/cdrom /mnt # Mount a CD-ROM
mount /image.iso /media/iso-file -o loop # Mount ISO Files
mount --move [olddir] [newdir] # Move a Mount
umount /dev/sdb1 # Unmount a File System
umount -l [device] # Lazy Unmount
umount -f [device] # Forced Unmount
fdisk -l # Find the devicesecho "foo" > bar.txt # Overwrite file with content
echo "foo" >> bar.txt # Append to file with content
ls exists 1> stdout.txt # Redirect the standard output to a file
ls noexist 2> stderror.txt # Redirect the standard error output to a file
ls 2>&1 out.txt # Redirect standard output and error to a file
ls > /dev/null # Discard standard output and error
read foo # Read from standard input and write to the variable foogrep 'foo' /bar.txt # Search for 'foo' in file 'bar.txt'
grep 'foo' /bar -r # Search for 'foo' in directory 'bar'
grep 'foo' /bar -R # Search for 'foo' in directory 'bar' and follow symbolic links
grep 'foo' /bar -l # Show only files that match
grep 'foo' /bar -L # Show only files that don't match
grep 'Foo' /bar -i # Case insensitive search
grep 'foo' /bar -x # Match the entire line
grep 'foo' /bar -C # Add N line of context above and below each search result
grep 'foo' /bar -v # Show only lines that don't match
grep 'foo' /bar -c # Count the number lines that match
grep 'foo' /bar -n # Add line numbers
grep 'foo' /bar --colour # Add colour to outputsed 's/fox/bear/g' foo.txt # Replace fox with bear in foo.txt and output to console
sed 's/fox/bear/gi' foo.txt # Replace fox (case insensitive) with bear in foo.txt and output to console
sed 's/red fox/blue bear/g' foo.txt # Replace red with blue and fox with bear in foo.txt and output to console
sed 's/fox/bear/g' foo.txt > bar.txt # Replace fox with bear in foo.txt and save in bar.txt
sed 's/fox/bear/g' foo.txt -i # Replace fox with bear and overwrite foo.txtzip foo.zip /bar.txt # Compress bar.txt into foo.zip
zip foo.zip /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.zip
zip foo.zip /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.zip
zip -r foo.zip /bar # Compress directory bar into foo.zipgzip /bar.txt foo.gz # Compress bar.txt into foo.gz and then delete bar.txt
gzip -k /bar.txt foo.gz # Compress bar.txt into foo.gztar -czf foo.tgz /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.tgz
tar -czf foo.tgz /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.tgz
tar -czf foo.tgz /bar # Compress directory bar into foo.tgzunzip foo.zip # Unzip foo.zip into current directorygunzip foo.gz # Unzip foo.gz into current directory and delete foo.gz
gunzip -k foo.gz # Unzip foo.gz into current directorytar -xzf foo.tar.gz # Un-compress foo.tar.gz into current directory
tar -xf foo.tar # Un-combine foo.tar into current directoryshutdown # Shutdown in 1 minute
shutdown now "message" # Immediately shut down
shutdown +5 "message" # Shutdown in 5 minutes
shutdown -r # Reboot in 1 minute
shutdown -r now "message" # Immediately reboot
shutdown -r +5 "message" # Reboot in 5 minutes
shutdown -c # Cancel a shutdown or reboot
reboot # Reboot now
reboot -f # Force a reboot * * * * *
Minute, Hour, Day of month, Month, Day of the weekcrontab -l # List cron tab
crontab -e # Edit cron tab in Vim
crontab /path/crontab # Load cron tab from a file
crontab -l > /path/crontab # Save cron tab to a file
* * * * * foo # Run foo every minute
*/15 * * * * foo # Run foo every 15 minutes
0 * * * * foo # Run foo every hour
15 6 * * * foo # Run foo daily at 6:15 AM
44 4 * * 5 foo # Run foo every Friday at 4:44 AM
0 0 1 * * foo # Run foo at midnight on the first of the month
0 0 1 1 * foo # Run foo at midnight on the first of the yearcurl https://example.com # Return response body
curl -i https://example.com # Include status code and HTTP headers
curl -L https://example.com # Follow redirects
curl -o foo.txt https://example.com # Output to a text file
curl -H "User-Agent: Foo" https://example.com # Add a HTTP header
curl -X POST -H "Content-Type: application/json" -d '{"foo":"bar"}' https://example.com # POST JSON
curl -X POST -H --data-urlencode foo="bar" http://example.com # POST URL Form Encoded
wget https://example.com/file.txt . # Download a file to the current directory
wget -O foo.txt https://example.com/file.txt # Output to a file with the specified name