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 |
Thanks !!!