The most essential Linux commands
Keep this Linux cheat sheet on your desk printed,
it will help you to learn them quickly and become a Linux expert very soon.
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File Commands
The linux ls command lists files and directories within the current working directory.
ls - directory listing
ls -al - formatted listing with hidden files
2) The cd Linux command changes the current directory in Linux and can toggle between directories conveniently.
cd dir - change directory to dir
cd - change to home
3) The pwd Linux command (print working directory) command displays the name of the current working directory.
pwd - show current directory
4) The mkdir (make directory) command is used to make a new directory.
mkdir dir - create directory dir
5) rm (short for remove) is a Unix / Linux command which is used to delete files from a filesystem.
rm file - delete file
rm -r dir - delete directory dir
rm -f file - force remove file
rm -rf dir - remove directory dir
6) The cp command is used to copies files and directories
cp file1 file2 - copy file1 to file2
7) mv (short for move) is a Unix command that moves one or more files or directories from one place to another.
mv file1 file2 - move file1 to file2
8) The link command creates a hard link named FILE2 which shares the same index node as the existing file FILE1. Since FILE1 and FILE2 share the same index node, they will point to the same data on the disk, and modifying one will be functionally the same as modifying the other.
ln -s file link - create symbolic link "link" to file
9) The touch command updates the access and modification times of each FILE to the current system time.
If you specify a FILE that does not already exist, touch creates an empty file with that name unless the -c or -h options are specified
touch file - create or update file
10) cat command It has three related functions with regard to text files: displaying them, combining copies of them and creating new ones.
cat > file - place standard input into file
11) more is a filter for paging through text one screen at a time.
more file - output the contents of the file
12) The less command lets an admin scroll through configuration and error log files, displaying text files one screen at a time, with backward or forward moving available in files.
less file - output the contents of the file
head file - output first 10 lines of file
tail -f file - output contents of file as it grows
linux ssh command
(SSH client) is a program for logging into a remote machine and for
executing commands on a remote machine, It is intended to replace rlogin
and rsh, and provide secure encrypted communications between two
untrusted hosts over an insecure network.
ssh [email protected] - connet tto host as user
ssh -P port [email protected] - connet using port p
ssh -D port [email protected] - connet and use bind port
Installation
Installing from source works on any GNU/Linux system that has the compiler and related tools and libraries, follows this route once you have a source package:
Unpack the archive and cd to its base directory.
Run the configure script ./configure
Compile the software make
Install the software make install
./configure
make
make install
basic linux commands for networking
ping is a simple way to send network data to, and receive network data from, another computer on a network. It is frequently used to test, at the most basic level, whether another system is reachable over a network, and if so, how much time it takes for that data to be exchanged
Ping host - ping host 'host'
whois searches for an object in a WHOIS database. WHOIS is a query and response protocol that is widely used for querying databases that store the registered users of an Internet resource, such as a domain name or an IP address block, but is also used for a wider range of other information.
whois domain - get whos for domain
The command dig is a tool for querying DNS nameservers for information about host addresses, mail exchanges, nameservers, and related information. This tool can be used from any Linux (Unix) or Macintosh OS X operating system. The most typical use of dig is to simply query a single host.
dig example.com
dig -x host - reverse lookup host
wget is a free utility for non-interactive download of files from the web. It supports HTTP, HTTPS, and FTP protocols, as well as retrieval through HTTP proxies.
wget file - download file
wget -c file - continue stopped download
wget -r url - recursively download file from url
System info
1) The date command is used to print out, or change the value of, the system’s time and date information.
date - show current date/time
2) Display a conveniently-formatted calendar from the command line.
cal - show this month's calendar
3) uptime tells you how long the system has been running.
uptime - show uptime
4) The w command is a quick way to see who is logged on and what they are doing.
w - display who is online
5) This command prints the username associated with the current effective user ID
whoami - who are you logged in as
6) Print information about the current system
uname -a - show kernel config
7) Show / check cpu information on Linux
cat /proc/cpuinfo - cpu info
8) show/check memory information on Linux
cat /proc/meminfo - memory information
10) On Linux and other Unix-like operating systems, man is the interface used to view the system’s reference manuals.
man command - show manual for command
11) The df command reports the amount of available disk space being used by file systems
df - show disk usage
12) du command estimates and displays the disk space used by files.
du - show directory space usage
du -sh - human readable size in GB
13) Linux free- Command Displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel
free- show memory and swap usage
14) Linux whereis app command Locates the binary, source, and manual page files for a command.
whereis app - show possible locations of app
15) linux command which app
which app - show which app will be run by default
Searching
1) grep Linux command: grep, which stands for “global regular expression print,” processes text line by line and prints any lines which match a specified pattern
grep pattern files - search for pattern in files
grep -r pattern dir - search recursively for pattern in dir
locate file - find all instances of file
Process Management
1) ps displays information about a selection of the active processes.
ps - display currently active processes
ps aux - ps with alot of detail
2) kill is used to send a signal to a process
kill pid - kill process with pid "pid"
kill all proc - kill all processes named proc
3) bg is a job control command that resumes suspended jobs while keeping them running in the background.
bg - lists stopped/background jobs, resume stopped jobs in the background
4) the fg command continues a stopped job by running it in the foreground
fg - bring most recent job to foreground
fg n - brings job n to foreground
File Permissions
Linux chmod command is used to change the permissions of files or directories
chmod octal file – change permission of file
- 4 – read (r)
- 2 – write (w)
- 1 – execute (x)
- order: pwmer/group.world
ex:
chmod 777 - rwx for everyone
chmod 755 - rw for owner, rx for group/world
Compression
1) The tar program is used to create, maintain, modify, and extract files that are archived in the tar format
tar cf file.tar files - tar files into file.tar
tar xf file.tar - untar into current directory
tar tf file.tar - show contents of archive
- tar flags:
- c – create archive
- t – table of contents
- x – extract
- f – specifules filename
- z – use zip/gzip
- j – bzip2 compression
- k – do not overwrite
- T – files from file
- w – ask for confirmation
- V – verbose
2) Gzip reduces the size of the named files using Lempel-Ziv coding (LZ77). Whenever possible, each file is replaced by one with the extension .gz, while keeping the same ownership modes, access and modification times.
gzip file - compress file and rename to file.gz
gzip -d file.gz - decompress file.gz
Shortcuts
ctrl+c halts current command
ctrl+z stops current command
fg - resume stopped command in foreground
bg - resume stopped command in background
ctrl+d - log out of current session
ctrl+w - erases one word in current session
ctrl+u - erases whole lne
ctrl+r - reverse lookup of previous commands
!! - report last command
exit - log out of current session
VIM quitting
:x - exit, saving changes
:wq - exit, saving changes
:q - exit, if no changes
:q! - exit, ignore changes
inserting text
- i – insert before cursor
- I – insert before line
- a – append after cursor
- A – append after line
- o – open new line after cur line
- O – open new line before cur line
- r – replace one character
- R – replace many characters
motion
- h – move left
- j – move down
- k – move up
- l – move right
- w – move to next word
- W – move to next blank delimited word
- b – move to beginning of the word
- B – move to beginning of blank delimited word
- e – move to end of word
- E – move to end of blank delimited word
- ( – move a sentence background
- ) – move a sentence forward
- { – move paragraph back
- } – move paragraph forward
- $ – move to end of line
- nG – move to nth line of file
- :n – move to nth line of file
- G – move to last line of file
- fc – move forward to ‘c’
- Fc – move backward to ‘c’
- H – move to top of screen
- M – move to middle of screen
- L – move to bottom of screen
- % – move to associated (),{},[]
deleting text
- x – delete character to the right
- X – delete character to the left
- D – delete to the end of line
- dd – delete current line
- :d – delete current line
searching
- /string – search forward for string
- ?string – search back for string
- n – search for next instance of string
- N – for for previos instance of string
replace
- :s/pattern/string/flags – replace pattern with string, according to flags
- g – flag, replace all occurences
- c – flag, confirm replaces
- & – repoat last :s command
- files
- :w file – write to file
- :r file – read file in after line
- :n – go to next file
- :p go to previous file
- :e file – edit file
- !!cmd – replace line with output of cmd other
- u – undo last change
- U – undo all changes to line
this is really informative, thanks
you are welcome
Thank you for the command list, very useful commands!
you are more then welcome
great job. thx boys
thanks ..great job.
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