os haven't not communicate apps and hardware's.
os use running applications and perform some tasks.
application developed by program.
humans can't communicate with directly hardware's. EX (speakers)
hardware's understand to 0 and 1s
os is a program. (c,c++,python, shell ...)
humans communicate to hardwares with help of os.
Different type os :
windows os, Linux,mac,unix
windows :
GUI - BUILD in program - user friendly - paid os - virus attacks possible - not open source - not secure
CLI - Bulid in program
Linux:
512 gb - 4 cpu - 120gb
Linus is free and open source.
secure
Linux famous for CLI. and little bit basic GUI
created by linus Torvalds ;
unix paid.
unix have some drop backs that resolved made Linux
Linux has been lot of distributions.
Linux foundation - non profits organization
file system:
Basic commends
date - Today date
cal - month calendar
whoami - login user srtechops
pwd - print working directory - /home/srtechops
mkdir sample - make directory (folder)
mkdir sample/ - represent / directory
rmdir sample - remove directory
ls - list files and directories ( present directory)
mkdir - devops aws azure gcp ai - create multiple directory
rmdir - devops aws azure gcp ai - remove multiple directory
touch file.txt - create empty file
rm file.txt - remove empty file
cat :
cat commend used to read and write file can't update lines.
cat file.txt - show file content
cat - write file
cat > file.txt
html
css
js
git
ctrl+d save and exit
cat > file.txt over ride exacting content dlt old line add new lines (override)
python
Django
cat >> file.txt append lines
python
Django
cat -n sample.txt - number of lines (1 2 3)
tac sample.txt - revere order
CLI Text Editor
nano text editor
vi
vim
nano sample.txt
ctrl + o - save and write out
ctrl + exit -exit
vi text editor
vi sample.txt
i - insert mood
Escape
:wq! - save and quit
q - quit
q! - quit not save
echo :
print terminal
echo"welcome to devops class"
echo 'welcome to devops class'
echo"welcome to devops class" >> sample.txt - save content sample.txt
history:
history - show all commend history
history -d 55 - particular commend select and dlt
history -c - clear all history
history >> commends.txt - if not file ..this situation automatically create file.
nano sample.txt - if not file ..this situation automatically create file.
echo"welcome to devops class" >> sample.txt - if not file ..this situation automatically create file.
ls :
ls - list files and directories
ls -l - list detail information
ls -a - list hidden files
ls -l -r -reverse order
ls -l -t - list time based
ls -ltr - order reverse time
ls -F -file types - aws.txt sample/
ls Aws/ - list awa dir files
mv :
mv - multiple purposes rename,move,unhide files
mv js java - rename
mv srtech .srt1 - hide dir
mv .srt1 srtech - unhide dir
mv sample,txt .s1.txt - hide file
mv .s1.txt sample.txt - unhide filles
mv sample.txt aws/s1 -move files
mv sample.txt aws/ - move file ..if file name not mention same name create file automatically
mv aws/document - move dir
cd
cd aws - change dir
cd .. - backward
cd . - current dir
cd - - previous dir
cd ~ - home dir
cd ../../ - backward 2 dir
cd aws/ai/azure/gcp - absolute path
rmdir
rmdir aws/ - dlt empty dir
rm -r aws/ - recoersovely remove files
rm -rf aws/ - force perement delete
rm *.txt - select all ,txt files and remove
rm * - remove all files (global)
rm f* - remove starting letter f files. f1. txt, f3.txt
copy
cp sample.txt s1 - copy contents
cp sample.txt documents/ - copy file and create same name (documents/sample.txt)
cp sample.txt documents/s1.txt - cp destinations s1.txt
cp -r documents/ aws - copy directory
head
head sample.txt - top 10 lines
head -n 5 sample.txt - top 5 lines
tail
tail -f audit.log - monitoring live logs
tail sample.txt - last 10 lines
tail -n 2 sample.txt - last 2 lines
grep - search text
grep "git" sample.txt
grep -i "g" sample.txt - ignore k senstive (upper or lower)
grep -i -c "g" sample.txt - count
grep -i -n "g" sample.txt - numbers
grep -i -v "g" sample.txt - list not matching content
history | grep -i "ls" - list ls
history | grep -i -c "ls" - list ls count
Sed
With out opening nano vi text editor you can delete update or what you are want.
sed "s/c/c++" - c replace c++ not affect original file. Just display temporary.
sed -i "s/py/python programming"sample.txt
Affect original file
sed -i "s/py/python programming/I"sample.txt -
Affect Case sensitive
sed -i '$d' sample.txt _ dlt last one line
sed -i '2d' sample.txt _ dlt specific one line
sed -i '6,$d' sample.txt _ dlt set of lines 6 to last one line
Zip compress and archive
File size Compress panna, archive oru single folder Ullara files pottu veikka
zip devopstools.zip *. txt - compress file
zip -sf devopstools.zip - show files without unzip files.
Note you not unzip file.. Add or delete files in possible.
zip devopstools.zip sample - adding new file to already existing zip file
zip -d devopstools.zip sample
Dlt particular file in zip
Unzip devopstools.zip - extracting files
Set password
zip -e file.zip *.txt
tar archive
tar -cf myfiles.tar *.txt - create archive
tar -cvf myfiles.tar *.txt - bg archive apoo enna nadakuthunu paakalam.
tar -tf myfiles.tar - view files without extract
tar -tvf myfiles.tar - view files full details without extract
extract
tar -xf myfiles.tar - extract file
tar -xvf myfiles.tar - full details
dowload links:
wget
ssh protocol :
ipconfig - machine ip address
ssh srtchops@gmail.com
password: srt123
tar —czvf compressedfile.tar.gz *.txt
gpg —c myfiles .tar - ser pssword
gpg —d myfiles.tar.gpg > myfiles.tar -dlt passw
user management :
$ - normal user
-root user
su root
password: ____
user :
adduser ak - create user
passwd - set password ak
cat/etc/passwd- verify user account create or not
su ak - switch to ak user
group :
cat/etc/group- verify user account create or not
home dir :
cd ~ - /home/ak
deluser ak - dlt user group / user dlt agum..home dir dlt agathu
delt home dir
rm —r ak
rm —rf ak
userdel sangavi --remove - delt all home/userac/group
user name modification :
usermod -l ak ajith - ak to ajith rename
dir name change :
mv ak/ ajith/
grop rename:
groupmod -n ak ajith
password:
sudo su
passwd ak
top
kill 2693
kill -9 2693 force kill
logout
Group management:
create group - groupadd DevTeam
verify group - cat/etc/group
gpasswd -a ranjith DevTeam - add user to group
usermod -aG DevTeam ranjith - add user to group another way
gpasswd -d ranjith DevTeam - dlt user
groupdel DevTeam - dlt group
cat /etc/group - check group
lid -g DevTeam - list group numbers
search files - ls /etc/ | grep "g*”
log files :
cat /var/log/audit/audit.log
tail —n 1 /var/log/audit/audit.log
how to see group numbers :
lid -g DevTeam list group id
gpasswd —a ak devTeam - add group
gpasswd —a vk devTeam
usermod —aG devTeam prem - add group
gpasswd —d ak devTeam - dlt group
gpasswd —d vk devTeam
groupdel devTeam - dlt group
file permission:
change permission
chmod u+x welcome.txt user
chmod u+r welcome.txt
chmod u+w welcome.txt
chmod u+rwx welcome.txt add all permissions
remove permission:
chmod u-x welcome.txt user
chmod u-r welcome.txt
chmod u-w welcome.txt
chmod u-rwx welcome.txt remove all permissions
chmod g+x welcome.txt group
chmod g+r welcome.txt
chmod g+w welcome.txt
chmod g+rwx welcome.txt
remove permission:
chmod g-x welcome.txt group
chmod g-r welcome.txt
chmod g-w welcome.txt
chmod g-rwx welcome.txt
chmod o+x welcome.txt others
chmod o+r welcome.txt
chmod o+w welcome.txt
chmod o-rwx welcome.txt
remove permission:
chmod o-x welcome.txt others
chmod o-r welcome.txt
chmod o-w welcome.txt
chmod +x welcome.txt - Add all users permission execute
-rx-x-x
chmod -x welcome.txt - Add all users permission execute
number permission:
chmod 000 welcome.txt - no access rwe
chmod 777 welcome.txt - all access rwe
chmod 444 welcome.txt - rrr
chmod 111 welcome.txt - xxx
chmod 222 welcome.txt -www
chmod 41 welcome.txt - rx
chown harini hello.txt - change group owner
devTeam members access allowed hello.txt
user owner ownership change at time :
change dir ownership:
packeage manager
redhat os - yum ( yellow dog updater & modified)
ubuntu os - apt ( advanced package tool )
yum install git
yum remove git
rpm -qa show sys install apps
rpm -qa git - git install or not
rpm -q git - search git o or not
yum update
lat version net laa irunthu dowload pannum
sudo yum update os softwares repo ellam update agum
yum upgrade
andha download panna ella filesyum install pannum.
sudo yum upgrade ella software update agum
rpm - redhat package manager
which firebox - firebox file location
rpm -qa show sys install apps
rpm -q - particular app i or not
rpm -q -f /user/bin/firebox - firebox executable file path
rpm -q -l firebox - firebox i location all list files
ls /user/bin/firebox
ls -l /user/bin/firebox
rpm -e firebox - uninstall
rpm install firebox - install
yum install firebox - install
yum remove firebox - uninstall
dnf install git - yum advance future
file sudoers : user permissions
sudoers behave like root ..neccssary to user in sudo group
tail -f audit. log - see live log
tail -n 1 audit. log - live last log
how to give root power sudo power to normal user?
useradd anu
su - anu
visudo file :
cat /etc/sudoers
visudo - edit file
anu ALL=(ALL) ALL - all access
anu ALL=(ALL) /usr/bin/yum - update.dlt apps
anu ALL=(ALL) /usr/bin/yum install git - particular access
anu ALL=(ALL) /usr/bin/yum install * - i all apps
wheel:
cat /etc/group
wheel ALL=(ALL) ALL /usr/bin/yum
lid -g wheel - show wheel group
gpasswd -a anu wheel
sudo lid -g wheel - display wheel group members
os details:
cat/etc/os-release - os info
whereis git - git location
find -name f1.txt - location
find -type f - empty - list empty files
find / -name srtech -
find —type d —empty —delete
soft links and hard links :
shortcut's
ln sample.txt hardlink.txt
original file laa dlt ,edit vela nadantha shortcut filelyum affect agum.
hardlink laa orginal file dlt pannalayum shortcut file orginal file aa ran aagum.
ln -s sample.txt softlink.txt
original file laa dlt ,edit vela nadantha shortcut filelyum affect agum.
orignal file dlt panna softlink work agathu
process management:
ps - process status
ps -ef -
top
kill 786
kill -9 2569
✅ 1. Shutdown Immediately
sudo poweroff
sudo shutdown now
✅ 2. Shutdown After 1 Minute
sudo shutdown
(Default is 1-minute delay)
✅ 3. Shutdown at a Specific Time
sudo shutdown 22:00
(This shuts down at 10:00 PM)
✅ 4. Restart Instead of Shutdown
sudo reboot
✅ Cancel Scheduled Shutdown
sudo shutdown -c
https://youtu.be/kozgg-jUmZI?si=NN0ZPuNMaZHdsl7H
https://youtu.be/ugyNu96k5_Q?si=WPb2glcsFTZqWsGR
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