The Linux command line is a powerful tool for managing systems efficiently. Whether you’re using AlmaLinux (a Red Hat Enterprise Linux alternative), Ubuntu, or Debian, these commands form the foundation for everyday tasks like file manipulation, system monitoring, and networking. This article compiles the top 100 essential commands, categorized for clarity. We’ve focused on commands that work across these modern distributions, noting any distro-specific variations (e.g., package managers: apt for Ubuntu/Debian, dnf for AlmaLinux).

Each category includes a table with the command, a brief description, and an example usage. Examples assume you’re in a terminal; use sudo where elevated privileges are needed.

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1. File and Directory Management (Commands 1-20)

These commands handle navigation, creation, and manipulation of files and directories.

#	Command	Description	Example
1	ls	Lists directory contents.	ls -la (detailed list including hidden files)
2	pwd	Prints current working directory.	pwd
3	cd	Changes directory.	cd /etc
4	mkdir	Creates a new directory.	mkdir new_folder
5	rmdir	Removes an empty directory.	rmdir empty_folder
6	rm	Deletes files or directories.	rm -r folder (recursive)
7	cp	Copies files or directories.	cp file.txt /backup/
8	mv	Moves or renames files/directories.	mv old.txt new.txt
9	touch	Creates empty files or updates timestamps.	touch newfile.txt
10	ln	Creates hard or symbolic links.	ln -s source link (symbolic)
11	find	Searches for files in a directory hierarchy.	find . -name "*.txt"
12	locate	Finds files by name (uses database).	locate config.file
13	du	Estimates file/directory space usage.	du -sh /folder (human-readable summary)
14	df	Displays disk space usage.	df -h (human-readable)
15	file	Determines file type.	file image.jpg
16	stat	Displays file or filesystem status.	stat file.txt
17	tree	Lists directory contents in a tree-like format.	tree /path
18	dir	Lists directory contents (alternative to ls).	dir -l
19	fd	Fast alternative to find for file searching.	fd pattern
20	dd	Copies and converts files (e.g., for disk images).	dd if=input of=output

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2. Text Processing and Viewing (Commands 21-35)

Commands for viewing, editing, and manipulating text files.

#	Command	Description	Example
21	cat	Concatenates and displays file contents.	cat file.txt
22	less	Views file contents page by page.	less longfile.log
23	more	Similar to less, paginates output.	more file.txt
24	head	Displays the first lines of a file.	head -n 5 file.txt
25	tail	Displays the last lines of a file.	tail -f /var/log/syslog (follow)
26	grep	Searches for patterns in files.	grep "error" log.txt
27	egrep	Extended grep (supports more regex).	egrep "pattern1|pattern2" file
28	fgrep	Fixed-string grep (no regex).	fgrep "string" file
29	sed	Stream editor for filtering/transforming text.	sed 's/old/new/g' file.txt
30	awk	Pattern scanning and processing language.	awk '{print $1}' file.txt
31	sort	Sorts lines of text files.	sort -n numbers.txt (numeric)
32	uniq	Removes duplicate lines from sorted input.	sort file | uniq
33	cut	Extracts sections from lines of files.	cut -d':' -f1 /etc/passwd
34	tee	Reads from stdin and writes to stdout and files.	ls | tee output.txt
35	tr	Translates or deletes characters.	tr 'a-z' 'A-Z' < file.txt

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3. System Information and Monitoring (Commands 36-45)

Tools to check system status, resources, and logs.

#	Command	Description	Example
36	uname	Prints system information.	uname -a (all details)
37	uptime	Shows system uptime and load average.	uptime
38	free	Displays memory usage.	free -h (human-readable)
39	top	Interactive process viewer.	top
40	htop	Enhanced interactive process viewer.	htop
41	vmstat	Reports virtual memory statistics.	vmstat 1 5 (every second, 5 times)
42	iostat	Reports CPU and I/O statistics.	iostat
43	dmesg	Prints kernel ring buffer messages.	dmesg | grep error
44	journalctl	Queries systemd journal logs.	journalctl -u service (Distro note: systemd-based like Ubuntu, Debian, AlmaLinux)
45	who	Shows who is logged in.	who

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4. Process Management (Commands 46-55)

Commands for viewing and controlling processes.

#	Command	Description	Example
46	ps	Displays current processes.	ps aux (all users)
47	pstree	Displays processes in a tree.	pstree
48	kill	Terminates processes by PID.	kill -9 1234 (force kill)
49	killall	Kills processes by name.	killall firefox
50	nohup	Runs commands immune to hangups.	nohup script.sh &
51	bg	Sends a job to the background.	bg %1
52	fg	Brings a job to the foreground.	fg %1
53	jobs	Lists active jobs.	jobs
54	nice	Runs commands with modified priority.	nice -n 10 command
55	renice	Alters priority of running processes.	renice -n 5 -p 1234

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5. Networking (Commands 56-70)

Essential for network configuration, testing, and file transfer.

#	Command	Description	Example
56	ip	Manages network interfaces and routing.	ip addr show
57	ifconfig	Displays/configures network interfaces (deprecated in some distros).	ifconfig
58	ping	Tests network connectivity.	ping google.com
59	traceroute	Traces route to a host.	traceroute google.com
60	netstat	Displays network connections (deprecated).	netstat -tuln
61	ss	Investigates sockets (modern alternative).	ss -tuln
62	nslookup	Queries DNS name servers.	nslookup google.com
63	dig	DNS lookup utility.	dig google.com
64	host	Performs DNS lookups.	host google.com
65	wget	Downloads files from the web.	wget https://example.com/file
66	curl	Transfers data with URLs.	curl https://example.com
67	ssh	Securely connects to remote hosts.	ssh user@host
68	scp	Securely copies files over SSH.	scp file user@host:/path
69	rsync	Syncs files/directories locally or remotely.	rsync -av /src/ /dest/
70	iptables	Configures firewall rules.	iptables -L (list rules)

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6. Package Management (Commands 71-75)

Distro-specific: Use apt for Ubuntu/Debian, dnf for AlmaLinux (or yum as alias).

#	Command	Description	Example
71	apt	Manages packages on Debian/Ubuntu.	apt install package
72	dnf	Manages packages on AlmaLinux/Fedora.	dnf install package
73	yum	Older package manager (alias to dnf on AlmaLinux).	yum update
74	rpm	Handles RPM packages (low-level).	rpm -ivh package.rpm
75	apt-get	Older alternative to apt on Debian/Ubuntu.	apt-get upgrade

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7. User and Permission Management (Commands 76-85)

For managing users, groups, and access rights.

#	Command	Description	Example
76	useradd	Adds a new user.	useradd -m newuser
77	usermod	Modifies user accounts.	usermod -aG sudo user
78	userdel	Deletes a user.	userdel user
79	passwd	Changes user passwords.	passwd user
80	su	Switches user.	su - user
81	sudo	Executes commands as superuser.	sudo apt update
82	whoami	Displays current user.	whoami
83	chown	Changes file owner/group.	chown user:group file
84	chmod	Changes file permissions.	chmod 755 script.sh
85	chgrp	Changes group ownership.	chgrp group file

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8. Disk and Filesystem Management (Commands 86-95)

For partitions, mounting, and filesystem checks.

#	Command	Description	Example
86	fdisk	Manipulates disk partition tables.	fdisk -l (list partitions)
87	parted	Creates/manipulates partitions.	parted /dev/sda
88	mkfs	Builds a filesystem.	mkfs.ext4 /dev/sdb1
89	fsck	Checks and repairs filesystems.	fsck /dev/sdb1
90	mount	Mounts a filesystem.	mount /dev/sdb1 /mnt
91	umount	Unmounts a filesystem.	umount /mnt
92	blkid	Locates/prints block device attributes.	blkid
93	lsblk	Lists block devices.	lsblk
94	partx	Tells kernel about disk partitions.	partx -a /dev/sda
95	ncdu	Disk usage analyzer.	ncdu /

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9. Archiving and Compression (Commands 96-100)

For compressing and archiving files.

#	Command	Description	Example
96	tar	Archives files.	tar -czvf archive.tar.gz /dir
97	gzip	Compresses files.	gzip file.txt
98	gunzip	Decompresses gzip files.	gunzip file.txt.gz
99	zip	Creates zip archives.	zip archive.zip files
100	unzip	Extracts zip archives.	unzip archive.zip

These commands will empower you to handle most tasks on AlmaLinux, Ubuntu, or Debian. For more details, use man command or --help. Practice in a virtual machine to build confidence!