uname -a # Display Linux System Information
uname -r # Display kernel release information
uptime # Show how long the system has been running + load
hostname # Show system host name
hostname -i # Display the IP address of the host
last reboot # Show system reboot history
date # Show the current date and time
cal # Show this month calendar
w # Display who is online
whoami # Who you are logged in as
finger user # Display information about user
chmod octal file-name # Change the permissions of the file to octal
# Example
chmod 777 /data/test.c # Set rwx permission for owner, group, world
chmod 775 /data/test.c # Set rwx permission for owner, rx for group and world
chown owner-user file # Change owner of the file
chown owner-user:owner-group file-name # Change owner and group owner of the file
chown owner-user:owner-group directory/ # Change owner and group owner of the directory
dmesg # Detected hardware and boot messages
cat /proc/cpuinfo # CPU Model
cat /proc/meminfo # Hardware memory
cat /proc/interrupts # Lists the number of interrupts per CPU per I/O device
lshw # Displays information on hardware configuration of the system
lsblk # Displays block device related information in Linux
free -m # Used and free memory (-m for MB)
lspci -tv # Show PCI Devices
lsusb -tv # Show USB Devices
dmidecode # Show hardware info from the BIOS
hdparm -i /dev/sda # Show info about disk sda
hdparm -tT /dev/sda # Do a read speed test on disk sda
badblocks -s /dev/sda # Test for unreadable blocks on disk sda
ip address add 192.168.0.1 dev eth0 # Set an IP Address
ip addr show # Display all network interfaces and ip address
ethtool eth0 # Linux tool to show ethernet status
mii-tool eth0 # Linux tool to show ethernet status
ping host # Send echo request to test connection
whois domain # Get Whois information for domain
dig domain # Get DNS information for domain
dig -x host # Reverse lookup host
host google.com # Lookup DNS IP address for the name
hostname -i # Lookup local IP address
wget file # Download file
netstat -tupl # List all active listening ports
id # Show the active user id with login and group
last # Show last logins on the system
who # Show who is logged on the system
groupadd admin # Add group "admin"
useradd \ # Create user "sam"
-c "Sam Tomshi" \
-g admin -m sam
userdel sam # Delete user sam
adduser sam # Add user "sam"
usermod # Modify user information
tar cf home.tar home # Create tar named home.tar containing home/
tar xf file.tar # Extract the files from file.tar
tar czf file.tar.gz files # Create a tar with gzip compression
gzip file # Compress file and renames it to file.gz
rpm -i pkgname.rpm # Install RPM based package
rpm -e pkgname # Remove package
./configure
make
make install
ls -al # Display all information about files/directories
pwd # Show the path of the current directory
mkdir directory-name # Create a directory
rm file-name # Delete a file
rm -r directory-name # Delete a directory recursively
rm -f file-name # Forcefully remove a file
rm -rf directory-name # Forecfully remove the directory structure
cp file1 file2 # Copy file1 to file2
cp -r dir1 dir2 # Copy dir1 to dir2, create dir2 if it doesn't exist
mv file1 file2 # Rename source to dest / move the source to directory
ln -s /path/to/file-name link-name # Create a symbolic link to file-name
touch file # Create or update a file
cat > file # Place standard input into a file
more file # Output contents of a file
head file # Output first 10 lines of a file
tail file # Output last 10 lines of a file
tail -f file # Output the contents of file as it grows starting with the last 10 lines
gpg -c file # Encrypt file
gpg file.gpg # Decrypt file
wc # Print the number of bytes, words, and lines of a file
xargs # Execute command lines from standard input
grep pattern file # Search for patterns in a file
grep -r pattern dir/ # Search recursively for a pattern in a dir
locate file # Find all instances of a file
find /home/tom -name 'index*' # Find file names that start with index
find /home -size +10000k # Find files larger than 10000k in /home
ssh user@host # Connect to a host as a user
ssh -p port user@host # Connect to a host using a specific port
telnet host # Connect to the system using telnet port
# scp
scp file.txt server2:/tmp # Secure copy file.txt to remote host /tmp folder
# rsync
rsync -a /home/apps /backup/ # Sync source to destination
ps # Display your currently active process
ps aux | grep 'telnet' # Find all process id's related to telnet process
pmap # Memory map of process
top # Display all running processes
kill pid # Kill process with mentioned pid id
killall proc # Kill all processes named proc
pkill process-name # Send signal to a process with its name
bg # Resumes suspended jobs without bringing them to the foreground
fg # Brings the most recent job to the foreground
fg n # Brings job n to the foreground
df -h # Show free space on mounted filesystems
df -i # Show free inodes on mounted filesystems
fdish -l # Show disk partition sizes and types
du -ah # Display disk usage in human readable form
du -sh # Display total disk usage on the current directory
findmnt # Displays target mount point for all filesystems
mount device-path mount-point # Mount a device
cd .. # Go up one level of the directory tree
cd # Go to the $HOME directory
cd /test # Change to the /test directory
