Basic Commands

1. pwd – Print the current working directory.
   • Example: pwd
2. cd – Change the current directory.
   • Example: cd /home/user
3. ls – List directory contents.
   • Example: ls -l
4. cp – Copy files or directories.
   • Example: cp file.txt /home/user/backup/
5. mv – Move/rename files or directories.
   • Example: mv oldname.txt newname.txt
6. rm – Remove files or directories.
   • Example: rm file.txt
7. mkdir – Create a new directory.
   • Example: mkdir newdir
8. rmdir – Remove an empty directory.
   • Example: rmdir olddir
9. touch – Create a new empty file or update the timestamp of an existing file.
   • Example: touch newfile.txt
10. cat – Concatenate and display file contents.
    • Example: cat file.txt

File Viewing

11. less – View file contents one screen at a time.
    • Example: less file.txt
12. more – View file contents one screen at a time (less advanced than less).
    • Example: more file.txt
13. head – Display the first lines of a file.
    • Example: head -n 10 file.txt
14. tail – Display the last lines of a file.
    • Example: tail -n 10 file.txt
15. nano – Simple text editor in the terminal.
    • Example: nano file.txt
16. vim – Advanced text editor in the terminal.
    • Example: vim file.txt
17. grep – Search text using patterns.
    • Example: grep "pattern" file.txt
18. find – Search for files in a directory hierarchy.
    • Example: find /home/user -name "*.txt"
19. diff – Compare files line by line.
    • Example: diff file1.txt file2.txt
20. wc – Word, line, character, and byte count.
    • Example: wc file.txt

File Permissions

21. chmod – Change file modes or Access Control Lists.
    • Example: chmod 755 script.sh
22. chown – Change file owner and group.
    • Example: chown user:group file.txt
23. chgrp – Change group ownership.
    • Example: chgrp group file.txt

File Compression

24. tar – Archive files.
    • Example: tar -czvf archive.tar.gz /path/to/dir
25. zip – Compress files into a zip archive.
    • Example: zip archive.zip file1 file2
26. unzip – Extract files from a zip archive.
    • Example: unzip archive.zip
27. gzip – Compress files with gzip.
    • Example: gzip file.txt
28. gunzip – Decompress gzip files.
    • Example: gunzip file.txt.gz
29. bzip2 – Compress files with bzip2.
    • Example: bzip2 file.txt
30. bunzip2 – Decompress bzip2 files.
    • Example: bunzip2 file.txt.bz2

System Monitoring

31. top – Display system tasks.
    • Example: top
32. htop – Interactive process viewer.
    • Example: htop
33. ps – Report a snapshot of current processes.
    • Example: ps aux
34. df – Report file system disk space usage.
    • Example: df -h
35. du – Estimate file space usage.
    • Example: du -sh /home/user
36. free – Display memory usage.
    • Example: free -h
37. uptime – Tell how long the system has been running.
    • Example: uptime
38. who – Show who is logged on.
    • Example: who
39. uname – Print system information.
    • Example: uname -a
40. iostat – Report CPU and I/O statistics.
    • Example: iostat

Networking

41. ping – Send ICMP ECHO_REQUEST to network hosts.
    • Example: ping google.com
42. ifconfig – Configure a network interface.
    • Example: ifconfig eth0
43. ip – Show/manipulate routing, devices, policy routing, and tunnels.
    • Example: ip addr show
44. netstat – Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.
    • Example: netstat -tuln
45. ss – Another utility to investigate sockets.
    • Example: ss -tuln
46. wget – Non-interactive network downloader.
    • Example: wget http://example.com/file.zip
47. curl – Transfer data from or to a server.
    • Example: curl -O http://example.com/file.zip
48. scp – Secure copy (remote file copy program).
    • Example: scp file.txt user@remote:/path/to/dest/
49. ssh – OpenSSH SSH client (remote login program).
    • Example: ssh user@remote
50. ftp – File Transfer Protocol client.
    • Example: ftp ftp.example.com

Disk Management

51. fdisk – Partition table manipulator for Linux.
    • Example: fdisk /dev/sda
52. mkfs – Build a Linux file system.
    • Example: mkfs.ext4 /dev/sda1
53. mount – Mount a file system.
    • Example: mount /dev/sda1 /mnt
54. umount – Unmount a file system.
    • Example: umount /mnt
55. fsck – File system consistency check and repair.
    • Example: fsck /dev/sda1

User Management

56. useradd – Create a new user.
    • Example: useradd newuser
57. userdel – Delete a user account and related files.
    • Example: userdel newuser
58. usermod – Modify a user account.
    • Example: usermod -aG sudo newuser
59. passwd – Update a user’s authentication tokens.
    • Example: passwd newuser
60. groupadd – Create a new group.
    • Example: groupadd newgroup

Package Management (Debian/Ubuntu)

61. apt-get – APT package handling utility.
    • Example: apt-get update
62. apt-cache – Query the APT cache.
    • Example: apt-cache search package
63. dpkg – Debian package manager.
    • Example: dpkg -i package.deb
64. aptitude – High-level interface to the package manager.
    • Example: aptitude install package

Package Management (Red Hat/CentOS)

65. yum – Package manager for RPM-based distributions.
    • Example: yum install package
66. rpm – RPM package manager.
    • Example: rpm -ivh package.rpm
67. dnf – Modernized package manager for RPM-based distributions.
    • Example: dnf install package

System Control

68. systemctl – Control the systemd system and service manager.
    • Example: systemctl start service
69. service – Run a System V init script.
    • Example: service service start
70. shutdown – Halt, power-off or reboot the machine.
    • Example: shutdown -h now
71. reboot – Reboot the system.
    • Example: reboot
72. halt – Halt the system.
    • Example: halt
73. init – Change runlevel.
    • Example: init 0

Archive and Backup

74. rsync – Remote file and directory synchronization.
    • Example: rsync -av /source /destination
75. dd – Convert and copy a file.
    • Example: dd if=/dev/sda of=/dev/sdb

Text Processing

76. awk – Pattern scanning and processing language.
    • Example: awk '{print $1}' file.txt
77. sed – Stream editor for filtering and transforming text.
    • Example: sed 's/old/new/g' file.txt
78. cut – Remove sections from each line of files.
    • Example: cut -d' ' -f1 file.txt
79. sort – Sort lines of text files.
    • Example: sort file.txt
80. uniq – Report or omit repeated lines.
    • Example: uniq file.txt
81. tr – Translate or delete characters.
    • Example: tr 'a-z' 'A-Z' < file.txt
82. paste – Merge lines of files.
    • Example: paste file1.txt file2.txt
83. join – Join lines of two files on a common field.
    • Example: join file1.txt file2.txt
84. tee – Read from standard input and write to standard output and files.
    • Example: echo "Hello" | tee file.txt

Disk Usage

85. lsblk – List information about block devices.
    • Example: lsblk
86. blkid – Locate/print block device attributes.
    • Example: blkid
87. df – Report file system disk space usage.
    • Example: df -h

System Logs

88. dmesg – Print or control the kernel ring buffer.
    • Example: dmesg
89. journalctl – Query and display messages from the journal.
    • Example: journalctl -xe

Miscellaneous

90. alias – Create an alias for a command.
    • Example: alias ll='ls -l'
91. unalias – Remove an alias.
    • Example: unalias ll
92. env – Run a program in a modified environment.
    • Example: env VAR=value command
93. printenv – Print all or part of environment.
    • Example: printenv PATH
94. export – Set an environment variable.
    • Example: export PATH=/usr/local/bin:$PATH
95. date – Display or set the system date and time.
    • Example: date "+%Y-%m-%d %H:%M:%S"
96. cal – Display a calendar.
    • Example: cal
97. whoami – Print effective user ID.
    • Example: whoami
98. hostname – Show or set the system’s hostname.
    • Example: hostname
99. clear – Clear the terminal screen.
    • Example: clear
100. history – Show the command history. – Example: history

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