Linux : Basic Commands

Linux

https://null-byte.wonderhowto.com/how-to/linux-basics/

Folder Structure

• /bin -       These are the programs that make Linux run (ie., binaries in  LInux)
• /etc -       configuration files are stored(usually txt format )
• /dev -      similar to Windows device drivers.
• /var -       log files, among other files, are stored.

Note:

·         Linux is Case- Sensitive

·         Linux allows us to modify its commands by using switches

·         switches are usually letters preceded by the dash (-)

·         With most commands, you can also use either the -h switch or the --help switch after the command to obtain "help".

·         Binaries are the files that are the equivalent of executables in Windows.

·         Binaries are files that do something like echo, ls, cd, mv, etc.

·         Probably the most important variable in our environment is our PATH variable

Summary:

1.       Network : whoami, ifconfig, dig, find

2.       Editing    : touch, cat, more ,less ,Nano,grep­ ,head ,tail ,sed ,nl

3.       File and Folders    : Pwd ,cd ,ls, mkdir  ,cp ,mv(move /rename), which, whereis ,locate ,unzip, , tar xvf, chmod , nzip

4.       System   : apt-get install, gcc , ps ,PID, ./,top ,set, export, uname-a, lsmod ,modproble –v/-r/-l

5.       Misc: man, echo, PS1,clear

Commands

present working directory> pwd

move me up one level> cd ..

name of the user we're logged in> whoami

Change Directory (Cd)> cd /newfolder

Listing Command (Ls)

> ls

> ls –la

-a switch means all

-l switch, it gives us info on the security permissions, the size, etc.,

Result: drwxr—r-x ……

d- directory

read/write/execute            =owner

only read                               =group

                read/execute                       =others

Create a File (Touch)> touch newfile

Create a Directory (Mkdir) > mkdir newdirectory

Getting Help (Man) > man touch

Copying Files (Cp) > cp /etc/newfile /root

Moving Files (Mv) > mv /root/newfile /

Viewing Files (Cat, More, Less,Nano)

> cat README

> more README

> less README

> Nano README

To view beginning of the file

>head /etc/snort/snort.conf

>head -30 /etc/snort/snort.conf

To view last lines of the file>tail /etc/snort/snort.conf

Numbering Those Lines>nl snort.conf

I Grep That

Only display lines with “database” in snort.conf file

>cat /etc/snort/ snort.conf | grep database

I Sed That Works

Replace every occurrence of mysql > MySQL

>sed s/mysql/MySQL/g snort.conf > snort2.conf

If I want to only replace the third occurrence of the word mysql and save as snort2.conf

sed s/mysql/MySQL/3 snort.conf > snort2.conf

Networking (Ifconfig)>ifconfig

Changing IP Addresses>ifconfig eth0 192.168.1.115 netmask 255.255.255.0 broadcast 192.168.1.255

DNS (Domain Name Service)

Translates to the appropriate IP address.

Linux users will often refer to DNS as BIND,

>dig wonderhowto.com ns

WonderHowTo's email servers.

>dig wonderhowto.com mx

Add or remove new server in the file below:

/etc/resolv.conf

Finding Files in a Directory (Find)

> find -name aircarck-ng

> find /pentest -name aircrack-ng

PATH variable contains path to bin directory

> echo $PATH

> which ls

Finding Any File in Any Directory (Whereis)> whereis aircrack-ng

Finding Files Using the Database (Locate)>locate aircrack-ng

Unzip>unzip DVWA-1.0.8.zip -d /var/www

Command Line Package Management or Installer>apt-get install aircrack-ng

Untar>tar xvf aircrack-ng-1.2-beta1.tar

Complie>gcc aircrack-ng

Install>./aircrack-ng

Changing permissions (read ,write,edit -> owner,group,user)

                Rwx=4 2 1=7

                rwxrwxrwx =>Chmod 777 readme= Chmod owner, group, user

                rw- r- - r- - =Chmod644 = Chmod Owner read write rest is read only

Running Process

                >ps aux

                >PID 5143

                >ps –A   

top processes>top

Killing Processes

>kill 5143

>kill -9 = No prisoners

View Our Environment Variables

>set HISTSIZE=123             

>echo $HISTSIZE

Adding application to path>PATH=$PATH:/pentest/wireless/aircrack-ng

Changing Our Terminal Prompt

                >PS1= "World's Best Hacker: #"

                >export PS1

Start Apache Daemon

                Goto Applications -> Services -> HTTPD and click on apache start.

Open  browser http://localhost/

Apache's default webpage is /var/www/index.html.

                User can edit this to displayed whatever he wants

Damn Vulnerable Web Application (DVWA)

                >  nzip DVWA-1.0.8.zip -d /var/www

                > chmod 755 DVWA-1.0.8 

Checking the Kernel

>; –a

or

>cat /proc/version

To tune kernel options>less /etc/sysctl.conf

List all drivers (Add a Module ie., driver)

                > lsmod   (lsmod is old)

Or

> modprobe –l

Add a Module(driver)

                > modprobe foo

                Finding info about a module

                > modinfo -v {module-name-here}

Remove a module (Driver)> modprobe -r foo