Linux Commands from A to Z
Enhance your efficiency by mastering these essential Linux commands.
Linux is a powerful and versatile operating system, renowned for its command-line utilities that offer unparalleled control over the system. Whether you’re a system administrator, developer, or an enthusiast, understanding these commands can significantly streamline your workflow. In this comprehensive guide, we cover a wide array of Linux commands, organized alphabetically for easy reference.
Table of Contents
A
alias
The alias command allows you to create shortcuts for other commands, reducing repetitive typing and simplifying complex command lines.
Example:
1
alias ll='ls -la'
This command creates an alias ll for ls -la, allowing quicker access to detailed directory listings.
at
The at command schedules commands or scripts to run once at a specified time, ideal for tasks that don’t need regular scheduling.
Usage:
1
2
at 2pm
at> /path/to/script.sh
This schedules script.sh to run at 2 PM.
awk
awk is a powerful text-processing tool used for pattern scanning and processing. It can manipulate data files and generate reports.
Example:
1
awk '/search_pattern/ { action }' file.txt
This command searches for a pattern and performs an action when the pattern is found.
B
basename
The basename command extracts the file name from a given path, which is particularly useful in scripting.
Example:
1
basename /path/to/file.txt
Output:
1
file.txt
This helps in focusing on essential data, reducing unnecessary processing.
C
cal
The cal command displays a simple calendar in the terminal.
Usage:
1
cal
This shows the current month’s calendar, aiding in quick date references without switching contexts.
cat
cat concatenates and displays file content. It’s essential for viewing files quickly.
Example:
1
cat file.txt
This displays the content of file.txt.
cd
The cd (change directory) command navigates between directories.
Usage:
1
cd /path/to/directory
Efficient navigation reduces time waste, aligning with Lean principles.
chgrp
chgrp changes the group ownership of files or directories.
Example:
1
chgrp group_name file.txt
Proper permission management prevents errors and rework.
chmod
The chmod command modifies file permissions, crucial for security.
Example:
1
chmod 755 script.sh
Sets read, write, execute permissions appropriately.
chown
chown changes the ownership of files and directories.
Usage:
1
chown user:group file.txt
cp
The cp command copies files and directories.
Example:
1
cp source.txt destination.txt
cron
cron schedules recurring tasks, automating routine operations.
Usage:
Edit the crontab with:
1
crontab -e
Schedule tasks using cron expressions.
curl
curl transfers data from or to a server, supporting various protocols.
Example:
1
curl -O http://example.com/file.txt
Downloads file.txt from the server.
cut
The cut command removes sections from each line of files, useful for processing data.
Example:
1
cut -d',' -f1 file.csv
Extracts the first field from a CSV file.
D
date
Displays or sets the system date and time.
Usage:
1
date
Shows the current date and time.
dd
dd copies and converts files at a low level, often used for creating disk images.
Example:
1
dd if=/dev/sda of=/backup/image.img
Creates an image of the disk /dev/sda.
df
Displays disk space usage.
Usage:
1
df -h
Shows disk usage in a human-readable format.
diff
Compares files line by line.
Example:
1
diff file1.txt file2.txt
Highlights differences between two files.
dig
dig queries DNS name servers, useful for network troubleshooting.
Usage:
1
dig example.com
Retrieves DNS information for example.com.
dirname
Extracts the directory path from a file path.
Example:
1
dirname /path/to/file.txt
Output:
1
/path/to
du
Estimates file and directory space usage.
Usage:
1
du -sh /path/to/directory
Displays the size of a directory.
E
echo
Outputs the strings it is passed as arguments.
Example:
1
echo "Hello, World!"
Displays Hello, World!.
emacs
An extensible, customizable text editor.
Usage:
1
emacs file.txt
Opens file.txt in Emacs editor.
expand
Converts tabs to spaces in files.
Example:
1
expand -t 4 file.txt
Converts tabs to four spaces.
F
file
Determines the file type.
Usage:
1
file file.txt
Displays the type of file.txt.
find
Searches for files in a directory hierarchy.
Example:
1
find /path -name "filename"
Locates files named filename under /path.
findmnt
Displays a list of mounted file systems.
Usage:
1
findmnt
fmt and fold
Formats text to fit within a specified width.
Usage:
1
fmt -w 80 file.txt
Wraps text at 80 characters.
free
Displays memory usage.
Usage:
1
free -h
Shows memory usage in human-readable format.
fsck
Checks and repairs a Linux file system.
Usage:
1
sudo fsck /dev/sda1
G
grep
Searches for patterns in files.
Example:
1
grep "search_term" file.txt
Finds lines containing search_term.
groupadd
Creates a new user group.
Usage:
1
sudo groupadd group_name
groupdel
Deletes a user group.
Usage:
1
sudo groupdel group_name
groupmod
Modifies a user group.
Usage:
1
sudo groupmod -n new_name old_name
groups
Displays group memberships.
Usage:
1
groups username
H
head
Displays the first lines of a file.
Example:
1
head -n 5 file.txt
Shows the first five lines.
history
Shows command history.
Usage:
1
history
I
id
Displays user and group information.
Usage:
1
id username
J
jobs
Lists active jobs in the current shell session.
Usage:
1
jobs
L
less
Allows backward and forward navigation through a file.
Usage:
1
less file.txt
ln
Creates links between files.
Example:
1
ln -s /path/to/file.txt linkname
Creates a symbolic link.
locate
Finds files by name using a pre-built database.
Usage:
1
locate filename
ls
Lists directory contents.
Usage:
1
ls -la
Shows detailed list including hidden files.
lsof
Lists open files and the processes using them.
Usage:
1
lsof -i
Displays open network connections.
M
mkdir
Creates directories.
Usage:
1
mkdir new_directory
mkfs
Builds a Linux file system on a device.
Example:
1
sudo mkfs.ext4 /dev/sdb1
Formats the partition as ext4.
more
Displays files one screen at a time.
Usage:
1
more file.txt
mv
Moves or renames files and directories.
Usage:
1
mv oldname.txt newname.txt
N
nc (netcat)
A versatile networking utility for reading from and writing to network connections.
Example:
1
nc -l 1234
Listens on port 1234.
nohup
Runs a command immune to hangups.
Usage:
1
nohup script.sh &
nslookup
Queries Internet name servers.
Usage:
1
nslookup example.com
P
passwd
Changes user passwords.
Usage:
1
passwd username
paste
Merges lines of files.
Example:
1
paste file1.txt file2.txt
ping
Sends ICMP ECHO_REQUEST to network hosts.
Usage:
1
ping example.com
printf
Formats and prints data.
Example:
1
printf "Name: %s\n" "Linux"
ps
Reports a snapshot of current processes.
Usage:
1
ps aux
R
read
Reads a line from standard input.
Usage:
1
read variable
reboot
Reboots the system.
Usage:
1
sudo reboot
rename
Renames multiple files.
Example:
1
rename 's/old/new/' *.txt
rm
Removes files or directories.
Usage:
1
rm file.txt
rsync
Synchronizes files and directories.
Example:
1
rsync -av source/ destination/
S
scp
Securely copies files between hosts.
Usage:
1
scp file.txt user@remote_host:/path
screen
Terminal multiplexer for managing multiple sessions.
Usage:
1
screen
sed
Stream editor for filtering and transforming text.
Example:
1
sed 's/old/new/g' file.txt
seq
Generates sequences of numbers.
Usage:
1
seq 1 10
sleep
Delays for a specified amount of time.
Usage:
1
sleep 5
source
Executes commands from a file in the current shell.
Usage:
1
source script.sh
stat
Displays file or file system status.
Usage:
1
stat file.txt
T
tail
Displays the last part of files.
Usage:
1
tail -n 10 file.txt
tar
Archives files.
Example:
1
tar -cvf archive.tar /path/to/files
tee
Reads from standard input and writes to standard output and files.
Usage:
1
command | tee output.txt
time
Measures program execution time.
Usage:
1
time script.sh
timeout
Runs a command with a time limit.
Usage:
1
timeout 5s command
top
Displays real-time system processes.
Usage:
1
top
touch
Updates file timestamps or creates empty files.
Usage:
1
touch newfile.txt
tr
Translates or deletes characters.
Example:
1
tr '[:lower:]' '[:upper:]' < file.txt
type
Indicates how a command name is interpreted.
Usage:
1
type ls
U
ulimit
Controls user resource limits.
Usage:
1
ulimit -n 1024
uname
Prints system information.
Usage:
1
uname -a
uniq
Filters out repeated lines in a file.
Usage:
1
uniq file.txt
useradd
Creates a new user account.
Usage:
1
sudo useradd username
userdel
Deletes a user account.
Usage:
1
sudo userdel username
usermod
Modifies a user account.
Usage:
1
sudo usermod -aG groupname username
V
vim
A highly configurable text editor.
Usage:
1
vim file.txt
W
watch
Executes a program periodically.
Usage:
1
watch -n 5 command
wc
Counts lines, words, and bytes.
Usage:
1
wc file.txt
which
Shows the full path of shell commands.
Usage:
1
which ls
who
Shows who is logged on.
Usage:
1
who
By familiarizing yourself with these commands, you can significantly enhance your productivity and reduce inefficiencies in your workflow, embodying an approach to continuous improvement.
Mastering Linux commands is essential for efficient system management and development. This comprehensive guide provides a foundation for understanding and utilizing these tools effectively.