Tag: linux commands

Wide range of Linux commands with their usage and descriptions

Here’s a more extensive HTML table of common Linux commands with their usage and descriptions:

Command Usage Description
ls ls [options] [directory] Lists the contents of a directory.
cd cd [directory] Changes the current directory to the specified directory.
mkdir mkdir [directory] Creates a new directory.
rm rm [options] [file] Deletes files or directories.
rmdir rmdir [directory] Removes an empty directory.
cp cp [options] source destination Copies files or directories.
mv mv [options] source destination Moves or renames files or directories.
touch touch [file] Creates an empty file or updates the timestamp of an existing file.
chmod chmod [options] mode file Changes file permissions.
chown chown [options] user[:group] file Changes file owner and group.
ps ps [options] Displays information about active processes.
kill kill [options] pid Terminates a process by its ID.
df df [options] Shows disk space usage.
du du [options] [directory] Shows disk usage of files and directories.
tar tar [options] file Archives files.
gzip gzip [file] Compresses files.
gunzip gunzip [file] Decompresses gzip files.
zip zip [options] zipfile files Creates a compressed archive.
unzip unzip [file.zip] Extracts files from a zip archive.
wget wget [options] url Downloads files from the internet.
curl curl [options] url Transfers data from or to a server.
ping ping [options] hostname Checks the network connection to a server.
top top Displays real-time system processes and resource usage.
nano nano [file] Opens a file in the Nano text editor.
vim vim [file] Opens a file in the Vim text editor.
echo echo [text] Displays a line of text or variable value.
cat cat [file] Displays the content of a file.
less less [file] Views the content of a file page by page.
head head [options] [file] Displays the first lines of a file.
tail tail [options] [file] Displays the last lines of a file.
find find [path] [options] Searches for files in a directory hierarchy.
locate locate [file] Finds the location of a file.
man man [command] Displays the manual page for a command.
ssh ssh [options] user@hostname Connects to a remote server via SSH.
scp scp [options] source destination Copies files between hosts over SSH.
sudo sudo [command] Executes a command as another user, typically root.
apt-get apt-get [options] command Manages packages on Debian-based systems.
yum yum [options] command Manages packages on Red Hat-based systems.
systemctl systemctl [command] Controls the systemd system and service manager.
service service [service] [command] Manages system services.
passwd passwd [options] [user] Changes a user’s password.
adduser adduser [options] user Adds a new user to the system.
deluser deluser [options] user Removes a user from the system.
crontab crontab [options] [file] Schedules regular tasks with cron.
alias alias name=’command’ Creates a shortcut for a command.
unalias unalias name Removes a command alias.
uname uname [options] Prints system information, such as the kernel name, version, and more.
hostname hostname Displays or sets the system’s hostname.
free free [options] Shows memory and swap usage.
df df [options] Shows disk space usage.
du du [options] [directory] Shows disk usage of files and directories.
history history Displays the list of previously executed commands.
uname uname -a Displays system information including the kernel version.
uptime uptime Shows how long the system has been running, including load averages.
who who Displays information about users currently logged into the system.
useradd useradd [options] username Adds a new user account.
usermod usermod [options] username Modifies a user account.
userdel userdel [options] username Deletes a user account.
groupadd groupadd [options] groupname Creates a new group.
groupdel groupdel groupname Deletes a group.
passwd passwd [options] [username] Changes a user’s password.
top top Displays real-time information about system processes and resource usage.
killall killall [process name] Terminates all processes with the specified name.
reboot reboot Reboots the system.
shutdown shutdown [options] [time] Shuts down the system.
mount mount [options] device directory Mounts a filesystem.
umount umount [options] directory Unmounts a filesystem.
fdisk fdisk [options] device Partition a hard disk.
mkfs mkfs [options] device Formats a filesystem on a device.
fsck fsck [options] [filesystem] Checks and repairs a filesystem.
df df [options] Reports the amount of disk space used and available on filesystems.
du du [options] [directory] Estimates file space usage.
ln ln [options] source [target] Creates hard and symbolic links between files.
tee tee [options] [file] Reads from standard input and writes to standard output and files.
chmod chmod [options] mode file Changes file modes or Access Control Lists (ACLs).
chown chown [options] user[:group] file Changes file owner and group.
chgrp chgrp [options] group file Changes the group ownership of a file.
dd dd [options] [if=file] [of=file] Converts and copies a file.
grep grep [options] pattern [file] Searches for patterns in files.
sed sed [options] script [file] Stream editor for filtering and transforming text.
awk awk [options] ‘program’ [file] A programming language that can be used for text processing and data extraction.
cut cut [options] file Removes sections from each line of files.
sort sort [options] file Sorts lines of text files.
uniq uniq [options] file Removes duplicate lines from a file.
diff diff [options] file1 file2 Compares files line by line.
comm comm [options] file1 file2 Compares two sorted files line by line.
head head [options] [file] Outputs the first part of files.
tail tail [options] [file] Outputs the last part of files.
paste paste [options] file1 file2 Merges lines of files side by side.
tr tr [options] set1 set2 Translates or deletes characters.
echo echo [options] string Displays a line of text.
expr expr expression Evaluates expressions.
bc bc An arbitrary precision calculator language.
xargs xargs [options] [command] Builds and executes command lines from standard input.
printf printf [format] [arguments] Formats and prints data.
date date [options] [+format] Displays or sets the system date and time.
cal cal [options] [month] [year] Displays a calendar.
uptime uptime Shows how long the system has been running.
whoami whoami Prints the current username.
env env [options] Displays or modifies the environment.
alias alias name=’command’ Creates an alias for a command.
unalias unalias name Removes an alias.
export export [variable] Sets an environment variable.
unexport unexport [variable] Unsets an environment variable.
seq seq [options] first last Prints a sequence of numbers.
basename basename [path] [suffix] Strips directory and suffix from filenames.
dirname dirname [path] Strips the last component from a file path.
bc bc [options] Interactive algebraic language calculator.
yes yes [string] Outputs a string repeatedly until killed.
nohup nohup command [arguments] Runs a command immune to hangups.
sleep sleep [number][suffix] Delays for a specified amount of time.
bc bc Basic calculator with support for floating-point arithmetic.
clear clear Clears the terminal screen.
jobs jobs Lists the active jobs.
fg fg [job] Brings a job to the foreground.
bg bg [job] Resumes a suspended job in the background.
disown disown [job] Removes jobs from the job table.
type type [command] Describes how a command would be interpreted.
read read [options] variable Reads a line of input into a variable.
trap trap [command] [signal] Catches and handles signals.
wait wait [pid] Waits for processes to complete.
kill kill [signal] pid Sends a signal to a process.
pkill pkill [options] pattern Stops processes by name.
killall killall [options] name Kills processes by name.
bg bg [job] Resumes a job in the background.
fg fg [job] Brings a job to the foreground.
jobs jobs Lists background jobs.
alias alias name=’command’ Creates a shortcut for a command.
unalias unalias name Removes an alias.
echo echo [string] Displays a line of text.
cal cal [options] [month] [year] Displays a calendar.
yes yes [string] Outputs a string until killed.
bc bc [options] Interactive calculator.
time time [command] Measures the duration of a command’s execution.
uptime uptime Shows how long the system has been running.
who who Displays who is logged in.
w w Shows who is logged in and what they are doing.
users users Shows the currently logged-in users.
last last [options] [username] Shows the last logins of users.
lastb lastb [options] Shows the last bad login attempts.
uname uname [options] Displays system information.
df df [options] Shows disk space usage.
du du [options] [directory] Shows disk usage.
lsof lsof [options] Lists open files and the processes using them.
strace strace [options] command Traces system calls and signals in a process.
nc (netcat) nc [options] host port Performs network operations, such as port scanning, or file transfer.
tcpdump tcpdump [options] Captures and analyzes network packets.
rsync rsync [options] source destination Synchronizes files and directories between two locations.
screen screen [options] Manages multiple shell sessions within one terminal.
tmux tmux [options] Terminal multiplexer to manage multiple terminal sessions.
htop htop Interactive process viewer (an enhanced version of top).
vmstat vmstat [options] Reports virtual memory statistics.
iotop iotop [options] Monitors disk I/O usage by processes.
iftop iftop [options] Displays bandwidth usage on an interface.
arp arp [options] Displays or modifies the ARP (Address Resolution Protocol) cache.
arping arping [options] host Sends ARP requests to hosts to discover MAC addresses.
ip ip [options] object command Utility for managing network devices, addresses, routing, and more.
ipcs ipcs [options] Displays information about IPC (Inter-Process Communication) facilities.
ipcrm ipcrm [options] Removes IPC facilities, such as message queues, semaphores, and shared memory.
ss ss [options] Displays socket statistics.
traceroute traceroute [options] host Displays the route packets take to reach a network host.
tracepath tracepath [options] host Similar to traceroute but does not require superuser privileges.
nmap nmap [options] [target] Scans networks and hosts for open ports and services.
dig dig [options] [domain] Queries DNS servers for information about a domain.
host host [options] [domain] Performs DNS lookups.
ethtool ethtool [options] interface Displays or changes Ethernet device settings.
iptables iptables [options] Configures the Linux kernel’s network packet filtering rules.
ufw ufw [options] Uncomplicated Firewall, front-end for iptables to manage firewall rules.
fail2ban fail2ban-client [options] Monitors log files and bans IPs that show malicious signs.
logrotate logrotate [options] Automatically rotates, compresses, and removes old log files.
journalctl journalctl [options] Views logs collected by systemd’s journal service.
rsyslog rsyslogd [options] Rocket-fast system for log processing.
lsblk lsblk [options] Lists information about block devices.
blkid blkid [options] [device] Prints block device attributes like UUID, filesystem type, etc.
hdparm hdparm [options] device Gets or sets SATA/IDE device parameters.
lsusb lsusb [options] Lists USB devices connected to the system.
lspci lspci [options] Lists all PCI devices.
modprobe modprobe [options] module Adds or removes a module from the Linux kernel.
lsmod lsmod Displays loaded kernel modules.
insmod insmod module Inserts a module into the Linux kernel.
rmmod rmmod module Removes a module from the Linux kernel.
depmod depmod [options] Generates modules.dep and map files for kernel modules.
mkinitcpio mkinitcpio [options] Creates an initial ramdisk environment.
mkinitrd mkinitrd [options] Creates an initial ramdisk for preloading modules during boot.
dracut dracut [options] Another tool to generate initramfs images.
setfacl setfacl [options] [file] Sets file access control lists (ACLs).
getfacl getfacl [options] [file] Gets file access control lists (ACLs).
chattr chattr [options] [files] Changes file attributes on a Linux filesystem.
lsattr lsattr [options] [files] Lists file attributes on a Linux filesystem.
fuser fuser [options] [files] Identifies processes using files or sockets.
inotifywait inotifywait [options] [file] Waits for changes to files using inotify.
inotifywatch inotifywatch [options] [file] Watches changes to files using inotify.
ionice ionice [options] [command] Sets or gets the I/O scheduling class and priority of a program.
renice renice [options] [priority] [PID] Alters the priority of running processes.
lscpu lscpu Displays information about the CPU architecture.
lsns lsns [options] Lists information about Linux namespaces.
unshare unshare [options] [command] Runs a program with some namespaces unshared from the parent.
chroot chroot [new root] [command] Changes the root directory for a command or interactive shell.
pivot_root pivot_root [new root] [put old] Changes the current root filesystem.
dd dd if=[source] of=[destination] [options] Converts and copies files.
shred shred [options] [file] Overwrites a file to hide its contents, making recovery difficult.
stat stat [options] [file] Displays detailed information about a file or file system.
namei namei [options] pathname Follows a pathname until a terminal point is reached, showing the directory entries found along the way.
findmnt findmnt [options] Finds a filesystem, listing mount points.
hdparm hdparm [options] [device] Gets or sets SATA/IDE device parameters.
dmidecode dmidecode [options] Fetches and decodes the DMI table (hardware information).
lsscsi lsscsi [options] Lists information about SCSI devices.
lsblk lsblk [options] Lists information about block devices.
wget wget [options] [url] Retrieves files from the web using HTTP, HTTPS, and FTP.
curl curl [options] [url] Transfers data from or to a server using various protocols.
aria2c aria2c [options] [url] Downloads files from the web with multi-threading and parallelization.
jq jq [options] [file] Processes JSON data, like sed for JSON.
envsubst envsubst [options] [file] Substitutes environment variables in shell format strings.
rev rev [file] Reverses lines of a file or input.
column column [options] [file] Formats text into columns.
hexdump hexdump [options] [file] Displays file contents in hexadecimal, decimal, octal, or ASCII.
xdelta3 xdelta3 [options] Computes differences between files, commonly used for patching.
asciinema asciinema [command] Records and shares terminal sessions, with playback in the browser.
zless zless [file] Views compressed text files with paging (like less).
xxd xxd [options] [file] Creates a hex dump or does the reverse.
units units [options] Converts between different units of measurement.
cal cal [options] Displays a simple calendar.
factor factor [number] Prints the prime factors of a number.
seq seq [options] [first] [increment] [last] Generates a sequence of numbers.
bc bc [options] Arbitrary precision calculator language.
dc dc [options] Reverse-polish notation calculator.

 

Interesting Alternatives to Some of the Classic Linux Commands

Legacy commands were created several decades ago and while they do their intended jobs, their functionalities could be improved and the structure could be simplified.

This is why there exist ‘alternative’ tools that enhance the legacy UNIX/Linux commands. In this article, I am going to list some new CLI tools that you could use in place of the good old classic Linux commands.

HTTPie: Alternative to wget and curl

When it comes to downloading files in terminal, wget and curl are the two of the most common tools. Interestingly, not all distributions have curl, wget installed by default.

HTTPie does the same job but in a more human-friendly way. You have colorized, the formatted output which makes it easier to understand and debug.

Bat: Alternative to cat

The cat command is perhaps one of the first commands you learn. It does the job for viewing the contents of small text files.

But bat command takes it to the next level by adding features like syntax highlighting and Git integration. The pagination option is also available.

ncdu: Alternative to du command

The du command in Linux is used for checking the size of a directory. It’s not very straightforward command and it certainly doesn’t give a very good default output.

Compared to that, ncdu is a lot better than providing the relevant information at the first glance.

There are other features here such as showing the disk usage in graphs, sort the display and even delete directories interactively.It is based on ncurses and hence the ‘nc’ is added to ‘du’. A similar CLI tool is gdu which is a du replacement written in Go which gives it a performance boost.

fd: Alternative to the find command

The find command is one of the most powerful and most used Linux commands. It’s impossible to imagine that a sysadmin could survive without using the find command.

But the find command has a strange structure and it could be slow if you do a large set of find operations. A better and faster alternative is fd command. Written in Rust, fd is simpler and faster than its legacy competitor.

exa: Alternative to ls command

The exa CLI tool adds a few features while listing directory contents. It has better defaults and uses colors to distinguish file types and metadata. exa can also display a file’s extended attributes, as well as standard filesystem information such as the inode, the number of blocks, and a file’s various dates and times.

You can use the tree view to see directory structure. It also has built-in Git support to see what files have changed, committed and staged etc.

Duf: Alternative to the df command

The df command in Linux is used for checking disk space. While it works most of the time, an easier and better alternative is duf, a tool written in Go.

It gives you an overview of all the devices mounted which is easy to understand. You also have the ability to specify a directory/file name and check free space for that mount point.

With duf, you can sort the output, list indoe information and even save the output in JSON format.