Some Famous and Useful Linux (Ubuntu) Command

Hello Guys !!! Hope you all doing well.Today I am going to put Some most famous and useful Linux command(Ubuntu & RedHead) . I am putting it categories wise.

1 - SYSTEM INFORMATION

uname -a	# Display Linux system information
uname -r	# Display kernel release information
cat /etc/redhat-release	# Show which version of redhat installed
uptime	# Show how long the system has been running + load
hostname	# Show system host name
Hostname -I	# Display the IP adress 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

2 - HARDWARE INFORMATION

dmesg	# 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 ( -h for human readable, -m for MB, -g for GB.)
lspci -tv	# Display PCI devices
lsusb -tv	# Display USB devices
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 sda

3 - PERFORMANCE MONITORING AND STATISTICS

top	# Display and manage the top processes
htop	# Interactive process viewer (top alternative)
mpstat l	# 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 (Use /var/log/syslog for Debian based systems.)
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 updates

4 - USER INFORMATION AND MANAGEMENT

id	# 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 group

5 - FILE AND DIRECTORY COMMANDS

ls -la	# List all files in a long listing (detailed) format
pwd	# Display the present working directory
mkdir directory	# Create a directory
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. If destination exists, copy source_directory into destination, otherwise create destination with the contents of source_directory.
mv file1 file2	# Rename or move file1 to file2. If file2 is an existing directory, move file1 into directory file2
ln -s /path/to/file linkname	# Create symbolic link to linkname
touch file	# Create an empty file or update the access and modification times of file.
cat file	# View the contents of file
less file	# Browse through a text file
head file	# Display the first 10 lines of file
tail file	# Display the last 10 lines of file
tail -f file	# Display the last 10 lines of file and "follow" the file as it grows.

6 - PROCESS MANAGEMENT

ps	# 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 all 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

7 - FILE PERMISSIONS 8 8- NETWORKING

ifconfig -a	# Display all network interfaces and ip address
ifconfig 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 I P_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
wget http://domain.com/file	# Download h ttp://domain.com/file
netstat -nutlp	# Display listening tcp and udp ports and corresponding programs

9 - ARCHIVES (TAR FILES)

tar 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 compress
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.

10 - INSTALLING PACKAGES

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 p ackage .
sudo apt-get update sudo apt-get upgrade	# Use this command to update and upgrade your Ubuntu system weekly.it will applied all the latest patch given by Ubuntu system
sudo apt-get autoclean sudo apt-get autoremove	# clean and remove all unused file from your system
sudo apt-get install <package-name>	# install software in your ubuntu system
sudo apt-get remove <package-name>	# Uninstall a package from system
sudo apt-get add-apt-repository ppa : <repo-name>	# Install a third party package/software.

11 – SEARCH

grep 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
find /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 user
ssh -p port user@host	# Connect to host using Port

13 - DISK USAGE

df -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

14 - DIRECTORY NAVIGATION

cd ..	# To go up one level of the directory tree. (Change into the parent directory.)
Cd	# Go to the $HOME directory
cd /etc	# Change to the /etc directory

Happy Coding !!!!

Thanks

Saurabh

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