pwd – Displays the current working directory of the
terminal
/ - Root directory
echo – Command that writes its arguments to standard
output
eg echo
HI
HI
Eg x = 100
Echo $x ($ for variable name)
100
su – Used to switch to root user (so that super user
permissions can be used to execute commands
su username- Used to switch to a
different user.
sudo -
Executes only that command with root/ super user privileges.
Clear (ctrl + L)- to clear cli but won’t e deleted.
Scroll up to see the commands.
USE TAB KEY TO AUTOFILL.
IF MORE THAN 1 DIRECTORY, IT
DISPLAYS THEM
DIRECTORIES
Cd – change directory.
Cd
subfoldername
Cd ..
(previous folder, one step back)
$ means
home directory
Cd ~ or cd- this
commad also changes the directory to home directory
Cd /
-Changes the directory to root directory
Cd
‘xx yy’ – we specify the folder name in inverted commas because there is a
space in the folder name
Ls- list all content(subfolders) in the working
directory.
Ls
path- byy specifying the path after ls, the content in that path will be
displayed
Ls -l
– Using ‘l’ flag, listas al the contents along with its owner settings,
permissions and time stamp(long
format)
Ls -a
– Using ‘a’ flag, lists all the hidden contents in the specified directory.
Ls
–author – Using ‘—author’ flag lists the contents in the specified
directory along with its owner
Ls -S
– Using ‘S’ flag, sorts and lists all the contents in the specified
directory by size.
Ls
*.html – Using “” flag, lists only the contents in the directory of a
particular format.
Ls
-IS storelocation> file.text- Using “>” flag, copies the result of ls
command into a text file (file.text). if no store location, it gets saved in
home directory
We can run multiple of them at once eg ls -laS
vi filename - View file- click insert to edit
WORKING WITH FILE
Cat filename filename //this command is used to display the content
of text files and concatenate several files into one
Cat -b //This is used to add line numbers to non
blank lines
Cat -n //This is used to add line numbers to all
lines
Cat -s //This is used to squeeze blank lines into one
line
Cat -E //Shows
$ at end of each line
Cat > Filename.txt //What ever you type is save in
filename. Then press CTRL +D.
Cat filename.txt >> filename2.txt //what even
in filename gets concatenated to filename2. Filename2 then filename1
Grep //to search for a particular string/word in a
text file.
Grep options file.txt /Returns result for matching
string “options”.
Grep -I options file.txt //Returns the results for
case insensitive strings
Grep -n options file.txt // Returs the matching
strings along with their line number
Grep -v options file.tx //Returns the result of lines
not matching the search string
Grep – c options file.txt // Returns the no. of lines
with result string.
Sort //sort result of search
Sort file.txt //Sorts the contents of file.txt and
returns them in alphabetical order. We can do with multiple files
Sort -r file.txt //‘r’ flag returns the results in
reverse order
Sort -f file.txt //‘f’ flag does case insensitive
sorting.
Sort -n file.txt //‘n’ flag returns the results as
per numerical order
PIPE (|)
Output the result of one command as input to another command
(to perform two operations in the same command.
Grep dh File.txt File2.txt | sort //Searches for
string “dh’ from both files and sorts the results
Grep dh File.txt file2.txt | sort -r //sorts the
result in reverse order
WORKING WITH FILES AND DIRECTORIES
Cp //this command is used to copy files and
directories
Cp -i //Enter interactive mode; CLI asks before
overwriting files
Cp -n //does not overwrite the file.
Cp -u //Updates the destination file only when source
file is different form destination file.
Cp -R //recursive copy for copying directories;
Copies even hidden files
Cp -v //Verbose; Prints informative messages
Tip
Cp directory . (dot means the working directory)
Mv {options} source destination //destination full
need if under the same directory =’s subfolder then no problem
Mv -I //Enters interactive mode; CLI asks before
overwriting files.
Mv -u //Updates the destination file only when source
file is different from destination file
Mv -v //Verbose; Prints source and destination files
To move or copy files of one type
Cp *.filetype
destination- * means all files with .filetype
Mv fromwhere/whattype
Mkdir //This command is used to create a new
directory
Mkdir -p //creates both a new parent directory and a
sub-directory.
Mkdir –parents //this is also used to create a parent
directory and a sub-directory.
Mkdir -p file1/{multiple subdirectories separated by
comma} //This is used to create multiple subdirectories inside the new
parent directory.
-p to create a parent directory and then to continue
executing the commands
Rmdir //this command is used to remove the specified
directory(Empty)
Rmdir -p //Removes both the paret and child directory
Rmdir -pv //Removes all the parent and sub
directories along with the verbose.
Rm -r //removes even non empty directories.
Rm -rp //removes non empty directories including
parent and subdirectories.
WORKING WITH USER PERMISSIONS ‘’r’,
‘w’, ‘x’’
Block1 (1 letter)- file/DIR Type’
Block 2 – User permissions
Block 3– Group permissions
Block 4 - Other’s permissions block2,3,4 have rwx letters which,
- for blank which means that permission is not granted.
File Types
Normal File – ‘-’
Directory – ‘d’
Character Special File – ‘c’
Binary Special File – ‘b’
File permissions-
Read – ‘r’
Write –‘w’
Execute – ‘x’
Block f5 – Symbolic Links
Block 6- Owner name
Block 7 – Group name
Block 8- file size in kb
Block 9- Time stamp
Denotations
Users- ‘u’
Groups- ‘g’
Others-‘o’
All – ‘a’
Chmod //To change the access permissions of files and
directories
Chown //To change the owner of files and directories.
Chgrp //To change the group ownership of file and
directories.
Chmod g+wx filename
//This gives the write and execute permission to group members
The letter g means group + means giving rights, - is
removing rights, = is overwriting
Chown username filename //changes the owner of the
specified file
Chown username:groupname filename //change both the
owner and group ownership of the specified file
Chgrp groupname filename //changes the group ownership of the
specified file
UPDATE SOFTWARE
sudo yum install package-name //for RHEL (redhat, centos)
sudo apt-get install package-name // for Debian,
ubuntu
sudo dnf install package-name //for fedora
use -y //for yes as default confirmation
Java8 Installation
Sudo yum update
Update-alternative
Setting environment variables
Sudo gedit .bashrc //(go to cd or home directory)
Edit java location
Run source .bashrc
Tar files(compressed)
Gzip //to compress with .gx format
Gunzip // to
decompress .gz files
Tar //To compress and decompress files with .tar
format
Tar -cvf tar-file-name filename //Compresing files to
Tar format
Tar -xvf tar-file-name //Extracting/Decompressign
files in tar format
Environment Variable – They control the behaviour of the
software package installed on Linux. The path where the packages have been
installed will be specified in environment variables.
Printenv //Prints the list of all environment
variables
Echo $HOME //This will print the path of the home
directory of the user
Echo $PATH //It is a colon-separated list of
directories in which the shell looks for commands.
Echo $HOSTNAME //This will print the hostname
Echo $USERNAME //This will print the username
Echo $Lang
//This will print the language being used
Echo $BASH_VERSION //This will print the version of
this instance of bash
Regular expressions – regular Expression(RegEx) are used to
search through data
It can be piped along with ‘grep’ command to find patterns
of text in the files
|
Symbol
|
Explanation
|
|
.
|
Replaces any character
|
|
^
|
Matches the start of the string
|
|
$
|
Matches the preceding character zero or
more times
|
|
*
|
Matches the preceding character zero or
more times
|
|
?
|
Matches the preceding character one or
more times
|
|
()
|
Groups regular expressions
|
|
\
|
Represents special characters
|
Processes
An instance of a program is called a process
Any command given to Linux kernel starts a new process.
There can be multiple processes (instances) of the same
program
Top //list of processes
PID|USER|PR|NI|VRT|RES|SHR|S|%CPU|%MEM|TIME+|COMMAND
Process id
Username
Priority
Niceness value (opposite of priority)
Virtual memory
Shared memory
Status
CPU time
Physical memory used
Total CPU time
Command
Ctrl+ C to exit
Type program and enter eg Firefox + enter
Ctrl + Z or W. stop process(It will run in background)
Fg programname //foreground
Bg programname //background
Ps us //Processes started by user who typed this
command
Pidof process // gives the pid of the process
Kill 1010// terminates the process of pid 1111
CREATING USER
Sudo useradd user-name //Adding a new user
Sudo passwd username //Setting a password for that user
Sudo userdel user-name //Deleting that user
Sudo groupadd group-name //Adding a new group
Sudo groupdel group-name //Deleting that group
Sudo usermod -g group-name user-name //Adding a user
to a primary group
SSH(Secure
Shell) For Remote MachineAccess
Service iptables stop //Drops the IP table
Sudo chkconfig iptables off //Permanently disables
the IP table
Sudo gedit /etc/hosts //Add the bleow IP addresses in
both the master and slave’s hosts file
Master IP
Slave IP
Ip addr show //To show the Ip address
Sudo ip adder del ip-address dev eth1 //Deleting
existing IP
Sudo ip addr add ip-address/mask dev eth1 // Adding
IP at the master’s node or slave’s node
Ssh master//Running this commad at the slave node wil
give remote access to master
Ssh slave //Running this command at the master node
will give remote access to slave
Ifconfig – give net information
Exit //to logout
