📁 File Management
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ls – List directory contents
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cd – Change directory
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pwd – Print current directory path
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cp file1 file2 – Copy file1 to file2
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mv old new – Move or rename files
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rm file – Remove file
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mkdir folder – Create directory
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rmdir folder – Delete empty directory
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touch file – Create empty file
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stat file – Show file info (size, timestamps,
permissions)
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basename path – Get filename from path
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dirname path – Get directory name from path
🔧 System Information
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uname -a – Show complete system info (kernel,
architecture, hostname)
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hostname – Display current system hostname
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uptime – Show how long the system has been
running
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top – Display real-time CPU and memory
usage
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htop – Enhanced interactive process viewer (if
installed)
-
df -h – Disk space usage (human-readable)
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du -sh * – Folder sizes in current
directory
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free -m – Show memory usage in MB
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lscpu – CPU architecture and info
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lsblk – List block devices (disks and
partitions)
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dmesg – Show system boot and hardware
messages
👤 User Management
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whoami – Show current logged-in user
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id – Show UID, GID, and groups of user
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users – Show all users currently logged in
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adduser username – Add a new user
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passwd username – Set/change user password
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usermod -aG group username – Add user to
group
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groups username – Show groups a user belongs
to
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deluser username – Delete a user
-
who – Show who is logged in and from where
-
su - username – Switch to another user
account
🌐 Networking
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ping google.com – Check if host is
reachable
-
ip a – Show IP addresses and interfaces
-
ifconfig – Old tool for network interfaces (still
used)
-
netstat -tulnp – List listening ports and
services
-
ss -tuln – Faster replacement for netstat
-
curl ifconfig.me – Get public IP address
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traceroute domain.com – Show route packets
take
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dig example.com – DNS lookup
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nslookup example.com – Query name servers
-
nmap 192.168.1.1 – Scan ports on a target
(requires install)
📦 Package Management (Debian/Ubuntu)
-
apt update – Refresh package lists
-
apt upgrade – Upgrade all installed
packages
-
apt install <package> – Install a
package
-
apt remove <package> – Remove a
package
-
apt search <package> – Search for
packages
-
dpkg -i <file.deb> – Install .deb package
file manually
-
apt autoremove – Remove unused dependencies
-
apt clean – Clear local repository of retrieved
package files
🔄 Processes & Services
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ps aux – Show all running processes
-
top – Interactive real-time process viewer
-
htop – Enhanced process viewer (if
installed)
-
kill <PID> – Terminate process by PID
-
killall <process_name> – Terminate all
processes with name
-
systemctl status <service> – Show service
status (systemd)
-
systemctl start <service> – Start a
service
-
systemctl stop <service> – Stop a
service
-
systemctl restart <service> – Restart a
service
-
service <service> start|stop|restart –
Control services (SysV init)
🧪 Disk & Filesystems
-
df -h – Show disk space usage in human-readable
format
-
du -sh <directory> – Show total size of
directory
-
mount | umount – Mount or unmount
filesystems
-
lsblk – List block devices (disks and
partitions)
-
fdisk -l – Show partition tables
-
blkid – Show block device attributes like UUID and
type
-
tune2fs – Adjust ext2/3/4 filesystem
parameters
-
fsck /dev/sdX – Filesystem consistency check and
repair
🔐 Permissions & Ownership
-
chmod 755 file – Set file permissions
(rwxr-xr-x)
-
chown user:group file – Change owner and
group
-
ls -l file – List file with permissions and
ownership
-
umask – Show default permission mask for new
files
-
getfacl file – Get extended ACL permissions
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setfacl -m u:user:rwx file – Set extended ACL
permissions
🔍 Search & Filters
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grep 'pattern' file – Search text in files
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find /path -name 'file' – Find files by
name
-
locate file – Quickly find file by name (updatedb
index)
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awk '{print $1}' file – Pattern scanning and
processing
-
sed 's/old/new/g' file – Stream editor for text
substitution
-
cut -d',' -f1 file – Extract columns from
file
-
sort file – Sort lines alphabetically or
numerically
-
uniq file – Filter duplicate lines
🛠️ Bash & Scripting
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echo "Hello World" – Print text to terminal
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#!/bin/bash – Shebang to specify script
interpreter
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chmod +x script.sh – Make script executable
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./script.sh – Run executable script
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if [ condition ]; then ... fi – Basic if
statement
-
for i in {1..5}; do ... done – For loop
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while [ condition ]; do ... done – While
loop
-
read variable – Read input from user
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$? – Exit status of last command
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export VAR=value – Set environment variable