- Basic Commands
- File Viewing & Editing
- Search & Filter
- File Permissions
- User & Group Management
- Process Management
- Disk Usage & Storage
- Package Management
- Networking
- System Information
- Text Processing
- Compression & Archiving
Basic Commands
| Command | Description | Real-World Example |
|---|---|---|
pwd | Print the current working directory |
Input: pwd
Output: /home/user
|
ls |
List files and directories in the current location |
Input: ls
Output: Documents Downloads file.txt
|
cd |
Change the current directory |
Input: cd Documents
Output: (no output, just changes to Documents directory)
|
cp |
Copy files or directories |
Input: cp file.txt copy.txt
Output: (copy.txt created with same content as file.txt)
|
mv |
Move or rename files or directories |
Input: mv copy.txt archive/
Output: (copy.txt moved to archive/ directory)
|
rm |
Remove files or directories |
Input: rm file.txt
Output: (file.txt deleted)
|
touch |
Create a new empty file or update timestamp |
Input: touch newfile.txt
Output: (newfile.txt created)
|
mkdir |
Create a new directory |
Input: mkdir new_folder
Output: (new_folder created)
|
rmdir |
Remove an empty directory |
Input: rmdir old_folder
Output: (old_folder deleted if empty)
|
File Viewing & Editing
| Command | Description | Real-World Example |
|---|---|---|
cat file.txt |
Displays the full content of a file |
Input: cat file.txt
Output: Hello world! This is the file content.
|
less file.txt | View file content with scroll (page by page) |
Input: less file.txt
Output: (Shows file in pager; use ↑ ↓ to scroll, q to quit)
|
more file.txt | View file content page-by-page (simpler than less) |
Input: more file.txt
Output: (Displays first page; press space for next)
|
head file.txt | Display the first 10 lines of a file |
Input: head file.txt
Output: Line 1
Line 2
...
Line 10
|
tail file.txt | Display the last 10 lines of a file |
Input: tail file.txt
Output: Line 91
...
Line 100
|
nano file.txt | Open file in nano text editor (simple and beginner-friendly) |
Input: nano file.txt
Output: (Opens nano editor; use Ctrl+X to exit)
|
vim file.txt | Open file in Vim editor (advanced and powerful) |
Input: vim file.txt
Output: (Opens file in Vim; press i to edit, :wq to save and quit)
|
Search & Filter
| Command | Description | Real-World Example |
|---|---|---|
grep "hello" file.txt | Search for the word "hello" in file.txt |
Input: grep "hello" file.txt
Output: hello world, this is a test
|
find / -name file.txt |
Search for a file named "file.txt" starting at root |
Input: find / -name file.txt
Output: /home/user/Documents/file.txt
|
locate file.txt |
Quickly find file using a prebuilt database |
Input: locate file.txt
Output: /home/user/Documents/file.txt
|
which python |
Show the path of the python executable |
Input: which python
Output: /usr/bin/python
|
whereis python |
Locate the binary, source, and man pages for a command |
Input: whereis python
Output: python: /usr/bin/python /usr/share/man/man1/python.1.gz
|
echo 'file1 file2' | xargs rm |
Run rm on each word passed via pipe |
Input: echo 'file1 file2' | xargs rm
Output: (file1 and file2 deleted if they exist)
|
File Permissions
| Command | Description | Real-World Example |
|---|---|---|
chmod 755 script.sh |
Change file permissions (rwxr-xr-x) |
Input: chmod 755 script.sh
Output: (script.sh is now executable by owner, readable/executable by others)
|
chown user:group file.txt | Change the owner and group of a file |
Input: chown alice:devs file.txt
Output: (Ownership of file.txt changed to alice:devs)
|
chgrp devs file.txt | Change group ownership of a file |
Input: chgrp devs file.txt
Output: (Group of file.txt changed to devs)
|
umask | Show or set default permissions for new files |
Input: umask
Output: 0022
|
umask 0007 | Set new default permissions (restricts access for others) |
Input: umask 0007
Output: (New files will default to 770 permissions)
|
User & Group Management
| Command | Description | Real-World Example |
|---|---|---|
adduser alice | Add a new user named "alice" |
Input: sudo adduser alice
Output: Adding user `alice' ...
|
userdel alice | Delete an existing user |
Input: sudo userdel alice
Output: (User alice deleted)
|
usermod -aG sudo alice | Add user to the "sudo" group |
Input: sudo usermod -aG sudo alice
Output: (alice can now use sudo)
|
passwd alice | Change the password for user "alice" |
Input: sudo passwd alice
Output: Enter new UNIX password:
|
groupadd devs | Create a new group named "devs" |
Input: sudo groupadd devs
Output: (Group devs created)
|
groups alice | List all groups the user "alice" belongs to |
Input: groups alice
Output: alice : alice sudo devs
|
id alice | Display user ID, group ID, and group memberships |
Input: id alice
Output: uid=1001(alice) gid=1001(alice) groups=1001(alice),27(sudo),1002(devs)
|
whoami | Print the current user’s username |
Input: whoami
Output: alice
|
Process Management
| Command | Description | Real-World Example |
|---|---|---|
ps aux | Display a snapshot of all running processes |
Input: ps aux
Output: USER PID %CPU %MEM COMMAND
alice 1234 0.0 0.1 bash
|
top | Real-time display of running processes |
Input: top
Output: (Live list of processes; press q to quit)
|
htop | Interactive process viewer (enhanced top) |
Input: htop
Output: (Colorful, interactive process viewer)
|
kill 1234 | Terminate a process by PID |
Input: kill 1234
Output: (Process with PID 1234 is terminated)
|
killall firefox | Kill all processes by name |
Input: killall firefox
Output: (All firefox processes terminated)
|
nice -n 10 myscript.sh | Start a process with lower priority |
Input: nice -n 10 ./myscript.sh
Output: (myscript.sh runs with niceness 10)
|
renice -n -5 -p 1234 | Change the priority of an existing process |
Input: renice -n -5 -p 1234
Output: 1234 (process priority changed to -5)
|
jobs | List background jobs in current shell |
Input: jobs
Output: [1]+ Running ./script.sh &
|
fg %1 | Bring background job to foreground |
Input: fg %1
Output: (Brings job [1] to foreground)
|
bg %1 | Resume a suspended job in background |
Input: bg %1
Output: (Job [1] resumes in background)
|
Disk Usage & Storage
| Command | Description | Real-World Example |
|---|---|---|
df -h | Show disk space usage in human-readable format |
Input: df -h
Output: Filesystem Size Used Avail Use% Mounted on
/dev/sda1 50G 20G 28G 42% /
|
du -sh /home/alice | Show total size of a directory |
Input: du -sh /home/alice
Output: 2.1G /home/alice
|
mount /dev/sdb1 /mnt | Mount a device to a directory |
Input: sudo mount /dev/sdb1 /mnt
Output: (Device mounted to /mnt)
|
umount /mnt | Unmount a mounted device |
Input: sudo umount /mnt
Output: (Device unmounted from /mnt)
|
lsblk | List block devices |
Input: lsblk
Output: NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 50G 0 disk /
|
blkid | Show UUID and type of block devices |
Input: sudo blkid
Output: /dev/sda1: UUID="abcd-1234" TYPE="ext4"
|
fdisk -l | List all partitions on all disks |
Input: sudo fdisk -l
Output: Disk /dev/sda: 50 GiB
Device Boot Start End Sectors Size Id Type
/dev/sda1 2048 ...
|
parted /dev/sda | Interactive tool to manage partitions |
Input: sudo parted /dev/sda
Output: (parted prompt appears for interactive use)
|
Package Management
| Command | Description | Real-World Example |
|---|---|---|
apt update | Update package index |
Input: sudo apt update
Output: Hit:1 http://archive.ubuntu.com/ubuntu focal InRelease
|
apt install nginx | Install a package |
Input: sudo apt install nginx
Output: The following packages will be installed: nginx
|
dpkg -i package.deb | Install a .deb package manually |
Input: sudo dpkg -i package.deb
Output: Unpacking package.deb ...
|
yum install httpd | Install a package using YUM (older Red Hat/Fedora) |
Input: sudo yum install httpd
Output: Installed: httpd.x86_64
|
dnf update | Update all packages (Fedora/RHEL 8+) |
Input: sudo dnf update
Output: Dependencies resolved. Upgraded: ...
|
rpm -i package.rpm | Install an RPM package manually |
Input: sudo rpm -i package.rpm
Output: Preparing... ################################# [100%]
|
pacman -Syu | Update system and upgrade packages (Arch Linux) |
Input: sudo pacman -Syu
Output: :: Synchronizing package databases...
|
pacman -S firefox | Install a package on Arch-based systems |
Input: sudo pacman -S firefox
Output: resolving dependencies...
|
Networking
| Command | Description | Real-World Example |
|---|---|---|
ip a | Display IP address and network interfaces |
Input: ip a
Output: inet 192.168.1.10/24 brd 192.168.1.255 ...
|
ifconfig | Show or configure a network interface (older tool) |
Input: ifconfig
Output: eth0: inet 192.168.1.10 netmask 255.255.255.0
|
ping google.com | Send ICMP packets to test connectivity |
Input: ping google.com
Output: 64 bytes from google.com: icmp_seq=1 ttl=117 time=22 ms
|
netstat -tuln | List all listening ports and connections |
Input: netstat -tuln
Output: tcp 0.0.0.0:22 LISTEN
|
ss -tuln | Faster and more detailed alternative to netstat |
Input: ss -tuln
Output: LISTEN 0 128 0.0.0.0:22
|
curl https://example.com | Transfer data from or to a server (shows content) |
Input: curl https://example.com
Output: <html>...</html>
|
wget https://example.com/file.txt | Download files from the web |
Input: wget https://example.com/file.txt
Output: Saving to: ‘file.txt’
|
scp file.txt user@192.168.1.5:/home/user/ | Securely copy a file to another system |
Input: scp file.txt user@192.168.1.5:/home/user/
Output: file.txt 100% 12KB 150.0KB/s 00:00
|
rsync -av file.txt user@192.168.1.5:/home/user/ | Sync files/directories between systems |
Input: rsync -av file.txt user@192.168.1.5:/home/user/
Output: sending incremental file list
|
ssh user@192.168.1.5 | Securely log into a remote machine |
Input: ssh user@192.168.1.5
Output: Welcome to Ubuntu 22.04 LTS
|
System Information
| Command | Description | Real-World Example |
|---|---|---|
uname -a | Display all system information (kernel, architecture, etc.) |
Input: uname -a
Output: Linux myhost 5.15.0-84-generic #1 SMP ... x86_64 GNU/Linux
|
hostname | Show the system's hostname |
Input: hostname
Output: myhost
|
uptime | Shows how long the system has been running |
Input: uptime
Output: 14:03:26 up 3 days, 2:17, 2 users, load average: 0.16, 0.09, 0.07
|
free -h | Display memory usage (human-readable) |
Input: free -h
Output: Mem: 7.7Gi 2.1Gi 3.4Gi ...
|
vmstat | Report system performance (memory, CPU, I/O) |
Input: vmstat
Output: procs -----------memory---------- ---swap-- ...
|
lscpu | Display CPU architecture information |
Input: lscpu
Output: Architecture: x86_64
CPU(s): 4
|
lsmem | Show memory block information |
Input: sudo lsmem
Output: RANGE SIZE STATE ...
0x0000000000000000-0x000000007fffffff 2G online
|
dmesg | View kernel ring buffer (boot and hardware messages) |
Input: dmesg | tail
Output: [ 12.123456] eth0: link up
|
Text Processing
| Command | Description | Real-World Example |
|---|---|---|
awk '{print $1}' file.txt | Print the first column of a file or input stream |
Input: awk '{print $1}' employees.txt
Output: John
Alice
|
sed 's/foo/bar/g' file.txt | Replace all occurrences of "foo" with "bar" |
Input: sed 's/foo/bar/g' notes.txt
Output: bar is a placeholder text
|
cut -d',' -f1 names.csv | Cut and show the first field (using comma as delimiter) |
Input: cut -d',' -f1 names.csv
Output: John
Alice
|
sort names.txt | Sort lines alphabetically |
Input: sort names.txt
Output: Alice
John
Mike
|
uniq sorted.txt | Remove duplicate adjacent lines |
Input: uniq sorted.txt
Output: Alice
John
|
tr 'a-z' 'A-Z' | Translate lowercase to uppercase |
Input: echo "hello" | tr 'a-z' 'A-Z'
Output: HELLO
|
wc -l file.txt | Count the number of lines in a file |
Input: wc -l notes.txt
Output: 42 notes.txt
|
tee output.txt | Read from input and write to a file and stdout |
Input: echo "Log entry" | tee log.txt
Output: Log entry
(and writes to log.txt)
|
split -l 10 large.txt | Split a file into pieces with 10 lines each |
Input: split -l 10 large.txt
Output: xaa, xab, xac...
|
paste file1 file2 | Merge lines from two files side-by-side |
Input: paste names.txt ages.txt
Output: Alice 25
John 30
|
Compression & Archiving
| Command | Description | Real-World Example |
|---|---|---|
tar -cvf archive.tar file1 file2 | Create a tar archive |
Input: tar -cvf archive.tar file1.txt file2.txt
Output: file1.txt
file2.txt
|
tar -xvf archive.tar | Extract files from a tar archive |
Input: tar -xvf archive.tar
Output: file1.txt
file2.txt
|
gzip file.txt | Compress a file using gzip |
Input: gzip report.txt
Output: Creates report.txt.gz
|
gunzip file.txt.gz | Decompress a .gz file |
Input: gunzip report.txt.gz
Output: Extracts report.txt
|
bzip2 file.txt | Compress file using bzip2 |
Input: bzip2 data.txt
Output: Creates data.txt.bz2
|
xz file.txt | Compress file using xz |
Input: xz manual.txt
Output: Creates manual.txt.xz
|
zip archive.zip file1 file2 | Create a zip archive |
Input: zip archive.zip file1.txt file2.txt
Output: adding: file1.txt
adding: file2.txt
|
unzip archive.zip | Extract a zip archive |
Input: unzip archive.zip
Output: extracting: file1.txt
extracting: file2.txt
|
