| alias | Create shortcut names for long commands | alias ll='ls -l' |
| apt | Debian/Ubuntu package manager | sudo apt update && sudo apt upgrade |
| awk | Pattern scanning and processing language | awk '{print $1}' file |
| cat | Concatenate/display file content | cat /etc/passwd |
| cd | Change directory | cd /var/log |
| chmod | Change file permissions | chmod 755 script.sh |
| chown | Change file owner/group | chown user:group file |
| cp | Copy files/directories | cp -r src/ dest/ |
| cron | Schedule periodic jobs | crontab -e |
| curl | Transfer data from/to URLs | curl -O https://example.com/file |
| cut | Remove sections from lines | cut -d: -f1 /etc/passwd |
| df | Show disk usage | df -h |
| diff | Compare files line-by-line | diff file1 file2 |
| du | Show directory space usage | du -sh * |
| echo | Display text/variables | echo "Hello $USER" |
| export | Set environment variables | export PATH=$PATH:/opt/bin |
| find | Search for files/directories | find /var -name "*.log" |
| free | Show memory usage | free -m |
| grep | Search text patterns | grep -i error /var/log/syslog |
| gzip | Compress files | gzip large.txt |
| head | Show first lines of a file | head -n 20 file |
| history | List command history | history | grep docker |
| htop | Interactive process viewer | htop |
| id | Show user/group IDs | id |
| ifconfig | Configure network interfaces (deprecated) | ifconfig eth0 |
| ip | Modern network configuration | ip addr show |
| jobs | List active jobs | jobs -l |
| kill | Terminate processes | kill -9 PID |
| less | View file page-by-page | less /var/log/syslog |
| ln | Create links | ln -s /path/to/file linkname |
| ls | List directory contents | ls -al |
| lsof | List open files | lsof -i :80 |
| man | Show manual pages | man tar |
| mkdir | Create directories | mkdir -p /tmp/backup/$(date +%F) |
| more | View file (basic pager) | more README |
| mount | Mount filesystems | mount /dev/sdb1 /mnt |
| mv | Move/rename files | mv old new |
| netstat | Show network connections | netstat -tulpn |
| nice | Run program with modified priority | nice -n 19 ./longtask |
| nohup | Keep command running after logout | nohup ./script & |
| passwd | Change user password | passwd |
| pgrep | Find process IDs by name | pgrep -f nginx |
| ping | Test network reachability | ping 8.8.8.8 |
| ps | Show running processes | ps aux |
| pwd | Show current directory | pwd |
| rm | Remove files/directories | rm -rf node_modules |
| rmdir | Remove empty directories | rmdir olddir |
| rsync | Fast file copying/synchronization | rsync -avz local/ remote:/backup/ |
| scp | Secure copy over SSH | scp file user@host:/path |
| sed | Stream editor | sed 's/foo/bar/g' file |
| service | Manage system services | sudo service apache2 restart |
| shred | Securely delete files | shred -vz -n 3 file |
| shutdown | Shutdown or reboot system | sudo shutdown -h now |
| sleep | Delay execution | sleep 30 && echo "Done" |
| sort | Sort lines of text | sort -k2 -n file |
| ssh | Secure shell remote login | ssh user@host |
| stat | Show file status | stat /etc/hosts |
| su | Switch user | su - username |
| sudo | Execute command as superuser | sudo apt install git |
| tail | Show last lines of a file | tail -f /var/log/nginx/access.log |
| tar | Archive/extract files | tar czf backup.tar.gz folder/ |
| tee | Write stdout to file and screen | echo "test" | tee file |
| top | Dynamic process viewer | top |
| touch | Create empty file/update timestamp | touch newfile |
| tr | Translate/delete characters | echo "abc" | tr 'a-z' 'A-Z' |
| umask | Set default file permissions | umask 022 |
| unalias | Remove aliases | unalias ll |
| uname | Show system information | uname -a |
| uniq | Remove duplicate lines | sort file | uniq |
| unzip | Extract ZIP archives | unzip archive.zip |
| uptime | Show system uptime | uptime |
| useradd | Create new user | sudo useradd -m alice |
| usermod | Modify user account | sudo usermod -aG sudo alice |
| vi/vim | Text editor | vim file |
| w | Show logged-in users and activity | w |
| wc | Count lines/words/bytes | wc -l file |
| wget | Download files from web | wget https://example.com/file |
| which | Show full path of command | which python3 |
| who | Show logged-in users | who |
| whoami | Show current user | whoami |
| xargs | Build and execute commands from stdin | find . -name "*.bak" | xargs rm |
| yum/dnf | RHEL/CentOS package manager | sudo dnf install nginx |
| zip | Create ZIP archives | zip -r archive.zip folder/ |