# Linux-Basic

Unix -> Linux -> Ubuntu(ram 512), Debian

[TOC]

# File systems

## Basic cmd
ls,cd,cat,pwd
tocuh,mkdir,cp,mv,rm,file(determining file type )

## Search File

### find (search the file)

find -name password

find -name *.txt


### grep (search the content of file)

grep '12.23.4.1' access.log

wc -l access.log


## Permission

ls -la 


### su --login user2


# Shell Operator

## &

## &&


## > (overwrite)


## >>


# SSH


# Flag/switch


# Directory

## /etc

Store systems files

## /var

Store for variable files

## /root

/root = /home/root


## /tmp


# Download File

## wget (HTTP)


## scp



## Static file server


# Process

## kernel


## Viewing Process

ps

aux



### Real-time Static

top    

## Managing Process


- kill
- sigterm
- sigkill
- sigstop

## How do process start

### Name space


### Initial Start


## Getting Process

### systemd


### systemctl


## Process front/background in Linux

### echo


### Foreground process

fg


# Maintaining Systems

## Automation

cron


## package management


## logs


- fail2ban (Defense sowfware)