Navigation
pwd - present working directory
cd - change directory
ls - list directory contents

Manipulating files and directories
cp - copy files and directories
mv - move/rename files and directories
mkdir - create a directory
rm - remove files and directories
rmdir - remove empty directory
ln - create hard and soft links
file - determine file type
less- view file content

Know more about command
type - indicate how a command name is interpreted
which - displays which executable program will be executed
help - get help from shell builtin
man - displays manual page for command
whatis - displays one page of its manual page
alias - create an alias for a command

Redirection
cat - concatenate and view files
sort -sort lines of text
uniq - report and omit repeated lines
grep - print lines matching a pattern
head - output the first part of a file
tail - output the last part of a file
echo - display a line of text

Permission
id - display user identity
chmod - change a file’s mode
umask - set default file permissions
su - run a shell as another user
sudo - execute command as another user
chown - change a file’s owner
chgrp - change a file’s group ownership
passwd - change user’s password

Search for file
locate - Find files by name
find - Search for files in a directory hierarchy
touch - Change file times
stat - Display file or file system status

Processes
ps - report a snapshot of current process
top - display task
jobs - list active jobs
bg - place a job in the background
fg - place a job in the foreground
kill - send a signal to process
killall - kill process by name
shutdown - shutdown or reboot system

Shell Environment
printenv - print part or all of the environment
set -set shell options
export - expoert env to subsequently executed programs

Storage
mount - mount a file system
umount- unmount the file system
fsck - check and repair a file system
fdisk - manipulate disk partition table
mkfs - create a file system
dd - convert and copy a file
mkisofs - create an iso 9660 image file
cdrecord - write a data to optical storage media

Networking
ping - send an ICMP ECHO_REQUEST to network hosts
traceroute - print the route packets trace to a network host
ip -Show/manipulate routing, devices, policy routing, and tunnels
netstat - Print network connections, routing tables, interface statistics,masquerade connections, and multicast memberships

ftp-Internet file transfer program
wget - Non-interactive network downloader
ssh - OpenSSH SSH client (remote login program)

Archiving and Backup
gzip - Compress or expand files
bzip2 - A block sorting file compressor
tar - Tape archiving utility
zip - Package and compress files
rsync - Remote file and directory synchronization

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