Linux Commands Cheat-Sheet

[x32x01]

Linux is becoming well known because it’s more than just free software as it’s unusually a good operating system. Linux was first developed by Linus Torvalds at the University of Helsinki in Finland.

If you’ve never worked with Linux before, you may be confused as to why there are so many different versions of it available. Linux commands are not the same as standard Unix ones. Most of the commands are provided by the GNU project.

Back before the days of graphical desktops, the only way to interact with a Unix system was through a text command line interface (CLI) provided by the shell. The CLI allowed text input only, and could only display text and rudimentary graphics output.

If you’re just beginning to work on a Linux system in this year (2020), the abundance of commands might prove daunting. To help, the following lists present a sampling of commands on various topics such as Networking, File Management, Programming etc.

S.No	Commands	Description
1	uname -a	Display Linux system information
2	uname -r	Display kernel release information
3	cat /etc/redhat-release	Show which version of redhat installed
4	uptime	Show how long the system has been running + load
5	hostname	Show system host name
6	hostname -I	Display the IP addresses of the host
7	last reboot	Show system reboot history
8	date	Show the current date and time
9	cal	Show this month’s calendar
10	w	Display who is online
11	whoami	Who you are logged in as
12	dmesg	Display messages in kernel ring buffer
13	cat /proc/cpuinfo	Display CPU information
14	cat /proc/meminfo	Display memory information
15	free -h	Display free and used memory ( -h for human readable, -m for MB, -g for GB.)
16	lspci -tv	Display PCI devices
17	lsusb -tv	Display USB devices
18	dmidecode	Display DMI/SMBIOS (hardware info) from the BIOS
19	hdparm -i /dev/sda	Show info about disk sda
20	hdparm -tT /dev/sda	Perform a read speed test on disk sda
21	badblocks -s /dev/sda	Test for unreadable blocks on disk sda
22	top	Display and manage the top processes
23	htop	Interactive process viewer (top alternative)
24	mpstat 1	Display processor related statistics
25	vmstat 1	Display virtual memory statistics
26	iostat 1	Display I/O statistics
27	tail 100 /var/log/messages	Display the last 100 syslog messages (Use /var/log/syslog for Debian based systems.)
28	tcpdump -i eth0	Capture and display all packets on interface eth0
29	tcpdump -i eth0 ‘port 80’	Monitor all traffic on port 80 ( HTTP )
30	lsof	List all open files on the system
31	lsof -u user	List files opened by user
32	free -h	Display free and used memory ( -h for human readable, -m for MB, -g for GB.)
33	watch df -h	Execute “df -h”, showing periodic updates
34	id	Display the user and group ids of your current user.
35	last	Display the last users who have logged onto the system.
36	who	Show who is logged into the system.
37	w	Show who is logged in and what they are doing.
38	groupadd test	Create a group named “test”.
39	useradd -c “John Smith” -m john	Create an account named john, with a comment of “John Smith” and create the user’s home directory.
40	userdel john	Delete the john account.
41	usermod -aG sales john	Add the john account to the sales group
42	ls -al	List all files in a long listing (detailed) format
43	pwd	Display the present working directory
44	mkdir directory	Create a directory
45	rm file	Remove (delete) file
46	rm -r directory	Remove the directory and its contents recursively
47	rm -f file	Force removal of file without prompting for confirmation
48	rm -rf directory	Forcefully remove directory recursively
49	cp file1 file2	Copy file1 to file2
50	cp -r source_directory destination	Copy source_directory recursively to destination. If destination exists, copy source_directory into destination, otherwise create destination with the contents of source_directory.
51	mv file1 file2	Rename or move file1 to file2. If file2 is an existing directory, move file1 into directory file2
52	ln -s /path/to/file linkname	Create symbolic link to linkname
53	touch file	Create an empty file or update the access and modification times of file.
54	cat file	View the contents of file
55	less file	Browse through a text file
56	head file	Display the first 10 lines of file
57	tail file	Display the last 10 lines of file
58	tail -f file	Display the last 10 lines of file and “follow” the file as it grows.
59	ps	Display your currently running processes
60	ps -ef	Display all the currently running processes on the system.
61	ps -ef | grep processname	Display process information for processname
62	top	Display and manage the top processes
63	htop	Interactive process viewer (top alternative)
64	kill pid	Kill process with process ID of pid
65	killall processname	Kill all processes named processname
66	program &	Start program in the background
67	bg	Display stopped or background jobs
68	fg	Brings the most recent background job to foreground
69	fg n	Brings job n to the foreground
70	ifconfig -a	Display all network interfaces and ip address
71	ifconfig eth0	Display eth0 address and details
72	ethtool eth0	Query or control network driver and hardware settings
73	ping host	Send ICMP echo request to host
74	whois domain	Display whois information for domain
75	dig domain	Display DNS information for domain
76	dig -x IP_ADDRESS	Reverse lookup of IP_ADDRESS
77	host domain	Display DNS ip address for domain
78	hostname -i	Display the network address of the host name.
79	hostname -I	Display all local ip addresses
80	wget http:// domain .com/file	Download http:// domain .com/file
81	netstat -nutlp	Display listening tcp and udp ports and corresponding programs
82	tar cf archive.tar directory	Create tar named archive.tar containing directory.
83	tar xf archive.tar	Extract the contents from archive.tar.
84	tar czf archive.tar.gz directory	Create a gzip compressed tar file name archive.tar.gz.
85	tar xzf archive.tar.gz	Extract a gzip compressed tar file.
86	tar cjf archive.tar.bz2 directory	Create a tar file with bzip2 compression
87	tar xjf archive.tar.bz2	Extract a bzip2 compressed tar file.
88	yum search keyword	Search for a package by keyword.
89	yum install package	Install package.
90	yum info package	Display description and summary information about package.
91	rpm -i package.rpm	Install package from local file named package.rpm
92	yum remove package	Remove/uninstall package.
93	tar zxvf sourcecode.tar.gz cd sourcecode ./configure make make install	Install software from source code.
94	grep pattern file	Search for pattern in file
95	grep -r pattern directory	Search recursively for pattern in directory
96	locate name	Find files and directories by name
97	find /home/john -name ‘prefix*’	Find files in /home/john that start with “prefix”.
98	find /home -size +100M	Find files larger than 100MB in /home
99	ssh host	Connect to host as your local username.
100	ssh user@host	Connect to host as user
101	ssh -p port user@host	Connect to host using port
102	scp file.txt server:/tmp	Secure copy file.txt to the /tmp folder on server
103	scp server:/var/www/*.html /tmp	Copy *.html files from server to the local /tmp folder.
104	scp -r server:/var/www /tmp	Copy all files and directories recursively from server to the current system’s /tmp folder.
105	rsync -a /home /backups/	Synchronize /home to /backups/home
106	df -h	Show free and used space on mounted filesystems
107	df -i	Show free and used inodes on mounted filesystems
108	fdisk -l	Display disks partitions sizes and types
109	du -ah	Display disk usage for all files and directories in human readable format
110	du -sh	Display total disk usage off the current directory
111	cd ..	To go up one level of the directory tree. (Change into the parent directory.)
112	cd	Go to the $HOME directory
113	cd /etc	Change to the /etc directory