Basic Commands

1. pwd – Print the current working directory.

• Example: pwd

1. cd – Change the current directory.

• Example: cd /home/user

1. ls – List directory contents.

• Example: ls -l

1. cp – Copy files or directories.

• Example: cp file.txt /home/user/backup/

1. mv – Move/rename files or directories.

• Example: mv oldname.txt newname.txt

1. rm – Remove files or directories.

• Example: rm file.txt

1. mkdir – Create a new directory.

• Example: mkdir newdir

1. rmdir – Remove an empty directory.

• Example: rmdir olddir

1. touch – Create a new empty file or update the timestamp of an existing file.

• Example: touch newfile.txt

1. cat – Concatenate and display file contents.

• Example: cat file.txt

File Viewing

1. less – View file contents one screen at a time.

• Example: less file.txt

1. more – View file contents one screen at a time (less advanced than less).

• Example: more file.txt

1. head – Display the first lines of a file.

• Example: head -n 10 file.txt

1. tail – Display the last lines of a file.

• Example: tail -n 10 file.txt

1. nano – Simple text editor in the terminal.

• Example: nano file.txt

1. vim – Advanced text editor in the terminal.

• Example: vim file.txt

1. grep – Search text using patterns.

• Example: grep "pattern" file.txt

1. find – Search for files in a directory hierarchy.

• Example: find /home/user -name "*.txt"

1. diff – Compare files line by line.

• Example: diff file1.txt file2.txt

1. wc – Word, line, character, and byte count.

• Example: wc file.txt

File Permissions

1. chmod – Change file modes or Access Control Lists.

• Example: chmod 755 script.sh

1. chown – Change file owner and group.

• Example: chown user:group file.txt

1. chgrp – Change group ownership.

• Example: chgrp group file.txt

File Compression

1. tar – Archive files.

• Example: tar -czvf archive.tar.gz /path/to/dir

1. zip – Compress files into a zip archive.

• Example: zip archive.zip file1 file2

1. unzip – Extract files from a zip archive.

• Example: unzip archive.zip

1. gzip – Compress files with gzip.

• Example: gzip file.txt

1. gunzip – Decompress gzip files.

• Example: gunzip file.txt.gz

1. bzip2 – Compress files with bzip2.

• Example: bzip2 file.txt

1. bunzip2 – Decompress bzip2 files.

• Example: bunzip2 file.txt.bz2

System Monitoring

1. top – Display system tasks.

• Example: top

1. htop – Interactive process viewer.

• Example: htop

1. ps – Report a snapshot of current processes.

• Example: ps aux

1. df – Report file system disk space usage.

• Example: df -h

1. du – Estimate file space usage.

• Example: du -sh /home/user

1. free – Display memory usage.

• Example: free -h

1. uptime – Tell how long the system has been running.

• Example: uptime

1. who – Show who is logged on.

• Example: who

1. uname – Print system information.

• Example: uname -a

1. iostat – Report CPU and I/O statistics.

• Example: iostat

Networking

1. ping – Send ICMP ECHO_REQUEST to network hosts.

• Example: ping google.com

1. ifconfig – Configure a network interface.

• Example: ifconfig eth0

1. ip – Show/manipulate routing, devices, policy routing, and tunnels.

• Example: ip addr show

1. netstat – Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.

• Example: netstat -tuln

1. ss – Another utility to investigate sockets.

• Example: ss -tuln

1. wget – Non-interactive network downloader.

• Example: wget http://example.com/file.zip

1. curl – Transfer data from or to a server.

• Example: curl -O http://example.com/file.zip

1. scp – Secure copy (remote file copy program).

• Example: scp file.txt user@remote:/path/to/dest/

1. ssh – OpenSSH SSH client (remote login program).

• Example: ssh user@remote

1. ftp – File Transfer Protocol client.

• Example: ftp ftp.example.com

Disk Management

1. fdisk – Partition table manipulator for Linux.

• Example: fdisk /dev/sda

1. mkfs – Build a Linux file system.

• Example: mkfs.ext4 /dev/sda1

1. mount – Mount a file system.

• Example: mount /dev/sda1 /mnt

1. umount – Unmount a file system.

• Example: umount /mnt

1. fsck – File system consistency check and repair.

• Example: fsck /dev/sda1

User Management

1. useradd – Create a new user.

• Example: useradd newuser

1. userdel – Delete a user account and related files.

• Example: userdel newuser

1. usermod – Modify a user account.

• Example: usermod -aG sudo newuser

1. passwd – Update a user’s authentication tokens.

• Example: passwd newuser

1. groupadd – Create a new group.

• Example: groupadd newgroup

Package Management (Debian/Ubuntu)

1. apt-get – APT package handling utility.

• Example: apt-get update

1. apt-cache – Query the APT cache.

• Example: apt-cache search package

1. dpkg – Debian package manager.

• Example: dpkg -i package.deb

1. aptitude – High-level interface to the package manager.

• Example: aptitude install package

Package Management (Red Hat/CentOS)

1. yum – Package manager for RPM-based distributions.

• Example: yum install package

1. rpm – RPM package manager.

• Example: rpm -ivh package.rpm

1. dnf – Modernized package manager for RPM-based distributions.

• Example: dnf install package

System Control

1. systemctl – Control the systemd system and service manager.

• Example: systemctl start service

1. service – Run a System V init script.

• Example: service service start

1. shutdown – Halt, power-off or reboot the machine.

• Example: shutdown -h now

1. reboot – Reboot the system.

• Example: reboot

1. halt – Halt the system.

• Example: halt

1. init – Change runlevel.

• Example: init 0

Archive and Backup

1. rsync – Remote file and directory synchronization.

• Example: rsync -av /source /destination

1. dd – Convert and copy a file.

• Example: dd if=/dev/sda of=/dev/sdb

Text Processing

1. awk – Pattern scanning and processing language.

• Example: awk '{print $1}' file.txt

1. sed – Stream editor for filtering and transforming text.

• Example: sed 's/old/new/g' file.txt

1. cut – Remove sections from each line of files.

• Example: cut -d' ' -f1 file.txt

1. sort – Sort lines of text files.

• Example: sort file.txt

1. uniq – Report or omit repeated lines.

• Example: uniq file.txt

1. tr – Translate or delete characters.

• Example: tr 'a-z' 'A-Z' < file.txt

1. paste – Merge lines of files.

• Example: paste file1.txt file2.txt

1. join – Join lines of two files on a common field.

• Example: join file1.txt file2.txt

1. tee – Read from standard input and write to standard output and files.

• Example: echo "Hello" | tee file.txt

Disk Usage

1. lsblk – List information about block devices.

• Example: lsblk

1. blkid – Locate/print block device attributes.

• Example: blkid

1. df – Report file system disk space usage.

• Example: df -h

System Logs

1. dmesg – Print or control the kernel ring buffer.

• Example: dmesg

1. journalctl – Query and display messages from the journal.

• Example: journalctl -xe

Miscellaneous

1. alias – Create an alias for a command.

• Example: alias ll='ls -l'

1. unalias – Remove an alias.

• Example: unalias ll

1. env – Run a program in a modified environment.

• Example: env VAR=value command

1. printenv – Print all or part of environment.

• Example: printenv PATH

1. export – Set an environment variable.

• Example: export PATH=/usr/local/bin:$PATH

1. date – Display or set the system date and time.

• Example: date "+%Y-%m-%d %H:%M:%S"

1. cal – Display a calendar.

• Example: cal

1. whoami – Print effective user ID.

• Example: whoami

1. hostname – Show or set the system’s hostname.

• Example: hostname

1. clear – Clear the terminal screen.

• Example: clear

1. history – Show the command history. – Example: history