- Opensource - Community support - Support wide variety of hardware - Customization - Most servers run on linux - Automation - Security

04 - LINUX Flashcards by Albert Dev

what is opensource ?

Software with source code that anyone can inspect, modify, and enhance.

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advantages of linux

Opensource
Community support
Support wide variety of hardware
Customization
Most servers run on linux
Automation
Security

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Architecture of linux

Hardware – kernel – shell – applications

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Popular linux distros

Ubuntu
Mint
Arch
Fedora
Debian
OpenSUSE

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Popular server linux OS

Red Hat Enterprise linux
Ubunu server
Centos
SUSE enterprise linux

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Most used linux distros

RPM based: RHEL, centos, Oracle
Debian based: ubuntu, kali linux

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what are the home directories

/root, /home/[username]

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user executable

/bin, /usr/bin, /usr/local/bin

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other mountpoints

/media, /mnt

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configurations

/etc

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Temporary files

/tmp

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kernels and bootloader

/boot

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server data

/var, /srv

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system information

/proc, /sys

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shared libraries

/lib, /usr/lib, /usr/local/lib

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command to switch to root user

su -i

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create file

touch filename.ext

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create multiple files in number range

Touch filename{1..10}.txt

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copy file to directory

cp file dev/

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relative vs absolute file path

relative: path from current directory
absolute: path from file system home directory

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copy directory with contents

cp -r /dir /main

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move or rename a file

mv src dest

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move all text files

mv *.txt dir/

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VIM editor modes

command, insert, extended

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create file in vim

move cursor to first/last line

set line numbers

copy paste in vim

yy/p, P

copy number of lines

nyy

delete line

undo

search keyword

/search

list files with detailed information

ls -l

get file type information

file filename

different filetypes

directory, file, character file, block disk, link, socket, pipe

create link to a file

ln -s destination link_name

list files sorted by timestamp

ls -lt

list files sorted from latest

ls -ltr

hostname location

/etc/hostname

search word in a file

grep keyword filename

search word in a file respect case

grep -i keyword filename

search word in directory

grep -iR *

less filename

top few lines from file

head filename

top 20 lines from file

head -20 filename

last n lines from file

tail -n filename

log files location

/var/log/

user information

/etc/passwd

slice terminal output

cut -d: -f1 /etc/passwd

using regex to split output

awk -f ':' '{print $1}' /etc/passwd

search and replace in VIM

:%s/searched_text/replaced_text [optional /g, //g]

search and replace from cmdline

sed ‘s.coronavirus/covid19/g’ filename or *

redirect cmd output to a file

ls > filename

show disk information

df -h

outputs a string of text

echo "text"

outputs to no where

echo "text" > /dev/null

append output to a file

cmd >> filename

appends error to a file

cmd 2>>filename

redirect and append

cmd &>>filename

number of words in file

wc -l filepath

use of pipe symbol

get users information

uid

user password location

/etc/passwd

types of users

root, regular, service

add a user

useradd username

user information

id username

add user to group

usermod -aG Group user

add user through group information file

/etc/groups

switch to user

su -username

list user open files

lsof -u username

delete user

userdel username

list files with permissions

ls -l

describe ls -l output

lrwxrwxrwx => file type, user, group others r read, w write, x execute

change file owner

chown -R ansible:devops /opt/devopsdir

remove file read permission from other users

chmod o-r /opt/devopsdir, -r

change file permission with numeric method

chmod 640 filepath

sudo users

/etc/sudoers, /etc/sudoers.d

visudo

download package with curl

curl package_name URL

install redhat package

rpm -ivh path

yum package management

yum repos

/etc/yum.repos.d /etc/apt/sources.list & /etc/apt/sources.list.d

starting a service

systemctl start httpd

is service enabled

systemctl is-enabled service_name

show running processes continuously

top

show running processes

ps aux

show running processes, search for httpd processes

ps -ef | grep httpd

stop a running process

kill process_id

archive file

tar -czvf source target, tar -xzvf source target

archive file commands

tar, zip