Command Reference
86+ commands with syntax, options, and practical examples. Search or browse by category.
Showing 86 of 86 commands
ls List directory contents
cd Change directory
pwd Print working directory name
cp Copy files and directories
mv Move or rename files and directories
mkdir Make directories
rm Remove files or directories
rmdir Remove empty directories
touch Change file timestamps or create empty files
cat Concatenate and display file content
grep Print lines matching a pattern
find Search for files in a directory hierarchy
less Opposite of more; view file content paginated
head Output the first part of files
tail Output the last part of files
awk Pattern scanning and processing language
sed Stream editor for filtering and transforming text
sort Sort lines of text files
uniq Report or omit repeated lines
wc Print newline, word, and byte counts for each file
diff Compare files line by line
chmod Change file mode bits (permissions)
chown Change file owner and group
sudo Execute a command as another user (superuser)
useradd Create a new user or update default new user information
usermod Modify a user account
userdel Delete a user account and related files
passwd Update user`s authentication tokens (passwords)
groupadd Create a new group
groupmod Modify a group definition on the system
groups Print the groups a user is in
id Print real and effective user and group IDs
ps Report a snapshot of current processes
top Display Linux processes (dynamic)
df Report file system disk space usage
du Estimate file space usage
free Display amount of free and used memory in the system
date Print or set the system date and time
uname Print system information
uptime Tell how long the system has been running
who Show who is logged on
ping Send ICMP ECHO_REQUEST to network hosts
ip Show / manipulate routing, network devices, interfaces
ssh OpenSSH SSH client (remote login program)
scp Secure copy (remote file copy program)
wget The non-interactive network downloader
curl Transfer data from or to a server
ss Another utility to investigate sockets
apt Package handling utility (Debian/Ubuntu)
tar GNU `tar` saves many files together into a single tape or disk archive, and can restore individual files from the archive.
gzip Compress or expand files
gunzip Decompress files compressed by gzip
kill Send a signal to a process
pkill Signal processes based on name and other attributes
killall Kill processes by name
jobs List active jobs
history Display command history
fg Bring a job to the foreground
bg Send a job to the background
shutdown Shut down or reboot the system
reboot Reboot the system
halt Halt the system
poweroff Power off the system
man Format and display the on-line manual pages
info Read Info documents
alias Create an alias for a command
unalias Remove an alias
echo Display a line of text
printf Format and print data
sleep Delay for a specified amount of time
read Read a line from standard input
true Do nothing, successfully (exit with 0)
false Do nothing, unsuccessfully (exit with 1)
tee Read from standard input and write to standard output and files
apt update Refresh available package information from configured sources.
apt upgrade Upgrade installed packages to their newest versions.
apt install Install new packages.
apt remove Remove packages.
apt search Search for a package by name or description.
systemctl Control the systemd system and service manager
journalctl Query the systemd journal (logs)
iptables Administration tool for IPv4 packet filtering and NAT
nft Administration tool for nftables (successor to iptables)
ufw Uncomplicated Firewall - frontend for iptables
htop Interactive process viewer and system monitor
lsof List open files and the processes that opened them