To know the user is using id command

id username

---

sudo

permits the user to execute a command as a super user at the admin level

---

su

su --> switch user
su -username
id 
exit

---

Zip

zip filename file
zip filename *.txt

zip -sf filename.zip
to view the zipped file.

unzip

unzip filename 

to make another directory to unzip the file or rename the exisisting file.

---

ulimit

to manage the resources of the particular user.

ulimit -a

soft limit cannot more than hard limit

cat  /etc/security/limits.conf

type> can have the two values:

-“soft” for enforcing the soft limits

– “hard” for enforcing hard limits

---

type

to know where the command it will present

type command

---

which 

where the command will locate

which mv

---

whatis

to know the description of the command

---

whereis

locate the binary, source, and manual page files for a command

---

apropos

search the manual page names and descriptions

---

change attribute

which makes the file unchangeable in the same location. but will copy the file in another location and edit the file.

sudo chattr +i filename

lsattr

sudo chattr -i file

it will convert unchangeable file to changeable file

sudo chattr -R +i dir1
sudo chattr -R -i dir1

to change the directory to unmutable

---

pidof ---> find the process ID of running program
vi test --> new process
ps -ef | grep vi 
pidof vi
pwdx 8279
to know the present working directory of vi using pid.

---

nice value

NI –> (-20 to 19) highest priority to lowest priority range.

1 to 19 –> non root users will aslo set the ni values

-20 to -1 –> root user only set the value

to modify the program priority.

ps -l --> process list
to change the priority of the running program
nice -n 11 ps -l

renice

changing the priority of the running program.

---

user-management

useradd

create a new user or update default new user information.

tail /etc/passwd –> userslist

adduser –> adduser, addgroup – add a user or group to the system

sudo passwd sample
to set a password for sample user.
sudo passwd -Sa
to check all the users having password or not.
set a password for the sample user

after setting the passwd for sample user

sudo passwd -d sample
d --> delete
NP --> no passwd

user-delete

sudo userdel sample
sudo userdel -r sample --> to delete with home

---

Group

to create group with user

to create a group

addgroup :

deletegroup :

sudo groupdel groupname
sudo delgroup groupname

sudo usermod -aG sudo username
permission to using i commands for new user
to give sudo or root previlage for new user.

To know the user is using id command

id username

---

sudo

permits the user to execute a command as a super user at the admin level

---

su

su --> switch user
su -username
id 
exit

---

Zip

zip filename file
zip filename *.txt

zip -sf filename.zip
to view the zipped file.

unzip

unzip filename 

to make another directory to unzip the file or rename the exisisting file.

---

ulimit

to manage the resources of the particular user.

ulimit -a

soft limit cannot more than hard limit

cat  /etc/security/limits.conf

type> can have the two values:

-“soft” for enforcing the soft limits

– “hard” for enforcing hard limits

---

type

to know where the command it will present

type command

---

which 

where the command will locate

which mv

---

whatis

to know the description of the command

---

whereis

locate the binary, source, and manual page files for a command

---

apropos

search the manual page names and descriptions

---

change attribute

which makes the file unchangeable in the same location. but will copy the file in another location and edit the file.

sudo chattr +i filename

lsattr

sudo chattr -i file

it will convert unchangeable file to changeable file

sudo chattr -R +i dir1
sudo chattr -R -i dir1

to change the directory to unmutable

---

pidof ---> find the process ID of running program
vi test --> new process
ps -ef | grep vi 
pidof vi
pwdx 8279
to know the present working directory of vi using pid.

---

nice value

NI –> (-20 to 19) highest priority to lowest priority range.

1 to 19 –> non root users will aslo set the ni values

-20 to -1 –> root user only set the value

to modify the program priority.

ps -l --> process list
to change the priority of the running program
nice -n 11 ps -l

renice

changing the priority of the running program.

---

user-management

useradd

create a new user or update default new user information.

tail /etc/passwd –> userslist

adduser –> adduser, addgroup – add a user or group to the system

sudo passwd sample
to set a password for sample user.
sudo passwd -Sa
to check all the users having password or not.
set a password for the sample user

after setting the passwd for sample user

sudo passwd -d sample
d --> delete
NP --> no passwd

user-delete

sudo userdel sample
sudo userdel -r sample --> to delete with home

---

Group

to create group with user

to create a group

addgroup :

deletegroup :

sudo groupdel groupname
sudo delgroup groupname

sudo usermod -aG sudo username
permission to using i commands for new user
to give sudo or root previlage for new user.

sudo apt install mariadb-server mariadb-client

sudo systemctl status mariadb.servcie

to check the mariadb services.

sudo systemctl enable mariadb.service

sudo systemctl start mariadb.service

sudo systemctl stop mariadb.service

sudo mysql_secure_installation

enter into the database using

mysql -u root -p

to view the default databases which present in mariadb using

show databases;

create new database using 
create database name;
show created database
show databases:
to use the exsisting database
use databasename;

jobs -l
t will dsiplay the job with process id

jobs -p
it will display only pid

fg % 1
foreground
ctrl + z to stop the job

bg % 2
we cannot stop  it runs in background

---

ps – process

report a snapshot for the current process

ps aux ---> it will dsiplay all users
ps x  

---

Kill

kill -9 pid1

used to kill the process

---

pstree

display running process in tree structure.

---

sudo apt install mariadb-server mariadb-client

sudo systemctl status mariadb.servcie

to check the mariadb services.

sudo systemctl enable mariadb.service

sudo systemctl start mariadb.service

sudo systemctl stop mariadb.service

sudo mysql_secure_installation

enter into the database using

mysql -u root -p

to view the default databases which present in mariadb using

show databases;

create new database using 
create database name;
show created database
show databases:
to use the exsisting database
use databasename;

jobs -l
t will dsiplay the job with process id

jobs -p
it will display only pid

fg % 1
foreground
ctrl + z to stop the job

bg % 2
we cannot stop  it runs in background

---

ps – process

report a snapshot for the current process

ps aux ---> it will dsiplay all users
ps x  

---

Kill

kill -9 pid1

used to kill the process

---

pstree

display running process in tree structure.

---

apache -> Hypertext transfer protocol webserver.

sudo apt install apache2 -y

install apache2 webserver in ubuntu.

sudo systemctl status apache2
apache2 status check

sudo systemctl enable apache2

persistently run across the reboot

cd /var/www/html

ubuntu default apache webpage.

sudo vim /etc/hosts

customize the localhost name 127.0.0.1 localhost to eladhruv.in. it will reflect only in local server.

rm index.html  -->  it removes default webpage
we customize the default page.

join file1 file2

join lines of two files on a common field. if no common fields are there then error should be occurs.

join -1 2 -2 1 s3.txt s4.txt

print unpairable lines using column number where FILE NUM is 1 or 2, corresponding to FILE1 or FILE2.

---

File

to determine the file type.

file filename
file -b filename
b -->  brief

file *

it display all the file type including directory.

---

touch

It will create a empty file the it will change the time snap.

touch filename

touch file{1..20}.txt

It will create 20 empty files. file size are user defined we can create more files.

touch -d tomorrow filename

It will change the day

touch -r s1.txt s2.txt
r -->  reference

time reference from s1.txt

---

Calendar

It display calendar

---

Reverse

Reverse the character

---

Redirection

> output Redirection | < input redirection

cat > filename
it will create a new file  and we can give input to the file

cat < filename
it will display the file content

 wc < text.txt > text1.txt
cat < text1
it will save the wc of the file to file1 

cat >> filename
adding the content to exisiting file
>> append

---

Tee

tee – read from standard input and write to standard output and files

df -Th | tee df.txt

---

Grep

grep – print lines that match patterns

grep "word" filename
grep "word" file1 file2
grep -i "word" file1 file2

---

join file1 file2

join lines of two files on a common field. if no common fields are there then error should be occurs.

join -1 2 -2 1 s3.txt s4.txt

print unpairable lines using column number where FILE NUM is 1 or 2, corresponding to FILE1 or FILE2.

---

File

to determine the file type.

file filename
file -b filename
b -->  brief

file *

it display all the file type including directory.

---

touch

It will create a empty file the it will change the time snap.

touch filename

touch file{1..20}.txt

It will create 20 empty files. file size are user defined we can create more files.

touch -d tomorrow filename

It will change the day

touch -r s1.txt s2.txt
r -->  reference

time reference from s1.txt

---

Calendar

It display calendar

---

Reverse

Reverse the character

---

Redirection

> output Redirection | < input redirection

cat > filename
it will create a new file  and we can give input to the file

cat < filename
it will display the file content

 wc < text.txt > text1.txt
cat < text1
it will save the wc of the file to file1 

cat >> filename
adding the content to exisiting file
>> append

---

Tee

tee – read from standard input and write to standard output and files

df -Th | tee df.txt

---

Grep

grep – print lines that match patterns

grep "word" filename
grep "word" file1 file2
grep -i "word" file1 file2

---

fmt filename

collecting all the words and making it us a paragraph

fmt -u filename

Removing unwanted spaces and making it us a paragraph

---

Head

head filename
head filename1 filename2

it display first 10 values. because default value is 10

head -q filename filname2

it display first 10 values in each file and name cannot be displayed.

---

Tail

tail -n 3 filename

It display last 3 values

tail -f filename

it will display realtime values

---

Numbering

nl filename

It will display the content with numbers and only used for numbering purpose.

nl -s "/" filename

to add a string using -s .

---

Split

split filename

It will split the content then create new file and it will save the splitted content into the new file.

split -l2 tech.txt split1.txt

It will split the content with two lines then create the new file and saved it into the splitted content.

---

Tac

 tac filename

it will reverse the content

---

Last

last 

displays a list of all users logged in (and out) since that file was created.

---

Translate

tr

Translate, squeeze, and/or delete characters from standard input, writing to standard output.

tr [a-z] [A-Z] < tech.txt | head -n 3 > translated.txt

---

Sed

sed ‘s/unix/linux/’ sample1.txt

sed  's/unix/linux/g'  sample1.txt

stream editor for filtering and transforming text.A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline). g –> globally change the content without g it will change only first word. s -> search.

---

Paste

paste -d "||" state.txt tech.txt | head -n 3

Merge lines of files. Write lines consisting of the sequentially corresponding lines from each FILE, separated by TABs, to standard output.

d –> delimeter , “|” it seperate the two merged files.

hostname -i

It displays host-id

hostname

It display hostname

$ --> it represent home
# --> it represent root

sudo su -

redirect to the root user

cd ~

to change history size using shell

which $SHELL

to know which shell is used.

vim ~/.bashrc

edit the history size and modify it.
press tab to auto fill the command

ls -a

to display the hidden files

ls -lah

to display hidden files with human readable

fmt filename

collecting all the words and making it us a paragraph

fmt -u filename

Removing unwanted spaces and making it us a paragraph

---

Head

head filename
head filename1 filename2

it display first 10 values. because default value is 10

head -q filename filname2

it display first 10 values in each file and name cannot be displayed.

---

Tail

tail -n 3 filename

It display last 3 values

tail -f filename

it will display realtime values

---

Numbering

nl filename

It will display the content with numbers and only used for numbering purpose.

nl -s "/" filename

to add a string using -s .

---

Split

split filename

It will split the content then create new file and it will save the splitted content into the new file.

split -l2 tech.txt split1.txt

It will split the content with two lines then create the new file and saved it into the splitted content.

---

Tac

 tac filename

it will reverse the content

---

Last

last 

displays a list of all users logged in (and out) since that file was created.

---

Translate

tr

Translate, squeeze, and/or delete characters from standard input, writing to standard output.

tr [a-z] [A-Z] < tech.txt | head -n 3 > translated.txt

---

Sed

sed ‘s/unix/linux/’ sample1.txt

sed  's/unix/linux/g'  sample1.txt

stream editor for filtering and transforming text.A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline). g –> globally change the content without g it will change only first word. s -> search.

---

Paste

paste -d "||" state.txt tech.txt | head -n 3

Merge lines of files. Write lines consisting of the sequentially corresponding lines from each FILE, separated by TABs, to standard output.

d –> delimeter , “|” it seperate the two merged files.

hostname -i

It displays host-id

hostname

It display hostname

$ --> it represent home
# --> it represent root

sudo su -

redirect to the root user

cd ~

to change history size using shell

which $SHELL

to know which shell is used.

vim ~/.bashrc

edit the history size and modify it.
press tab to auto fill the command

ls -a

to display the hidden files

ls -lah

to display hidden files with human readable

cat /proc/cpuinfo | wc

output of the first command goes to the input of the second command

cat /proc/cpuinfo | grep core

grep key is used to identified the matching words

---

vim

vim text1.txt --> create a file in vim editor
i to insert 
esc:wq! --> to save the file
vim text1.txt  --> to edit the file
esc:q!  --> to exit the editor

---

find

to search a file in particular directory and find a particular directory

find . -name text.txt

it will display the path where the file is saved.

find . -type d -name eclipse
find . -type f -name eclipse

f to find a file , d to find a directory

---

env

environment variable is useful written scripts

env   --> to display all env values
export name = elavarasu  --> to create env var and values

---

df -> to know the system space

df

to view the free spaces and used spaces in system.

df -h

to view the free spaces and used spaces with human readable format

df -h -total

to display total used and free spaces

---

less

to read a content one page at a time

less /prop/cpuinfo

use spacebar to read page by page

use up-arrow to read last line

use down-arrow to read line by line

use g to go the first line

use shift+g to last line

use q to quit

---

sort

to arrange in a particular order

sort filename

to sort a file content in a particular order

sort filename1 > filename2

to save the sorted content to another file

sort -u filename

to remove the duplicate file.

sort -u filename > uniq

It will display the unique value with sorted order

sort -u filename > uniq -d

It will display duplicate values with sorted order

sort sort.txt | uniq -i

It removes cases values

---

uniq

uniq filename

to display the unique content

uniq -c filename

to know how many time it will counted

---

cut

removing the section from each section of the file

cut -c1 filename

cut first character in a file

cut -c-5 filename

cut 5 characters from the beginning

wc filename

wc command calculates a file’s word, line, character, or byte count.

wc -l filename

It displays the count of number of lines.

wc -c filename

It displays count of bytes.

wc -m filename

It displays count of characters

---

copy command

cp filename1 filename2

to copy filename 1 to filaname2 for backup purpose

wc filename

wc command calculates a file’s word, line, character, or byte count.

wc -l filename

It displays the count of number of lines.

wc -c filename

It displays count of bytes.

wc -m filename

It displays count of characters

---

copy command

cp filename1 filename2

to copy filename 1 to filaname2 for backup purpose