Linux Command

Krishna Neupane

Jan 2, 2023

Command	Description
uname -a	Display Linux system information
uname -r	Display kernel release information
cat /etc/os-release	Show operating system information such as distribution name and version
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

Command	Description
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

Command	Description
top	Display and manage the top processes
htop	Interactive process viewer (top alternative)
mpstat 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 (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
free -h	Display free and used memory (-h for human readable, -m for MB, -g for GB.)
watch df -h	Execute "df -h", showing periodic updates

Command	Description
uname -a	Display Linux system information
uname -r	Display kernel release information
cat /etc/os-release	Show operating system information such as distribution name and version
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
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 "Krishna Neupane" -m krishna	Create an account named Krishna, with a comment of "Krishna Neupane" and create the user's home directory.
userdel Krishna	Delete the Krishna account.
usermod -aG sales krishna	Add the krishna account to the sales group

Command	Description
ls -al	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.

Command	Description
uname -a	Display Linux system information
uname -r	Display kernel release information
cat /etc/os-release	Show operating system information such as distribution name and version
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
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
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