⁍ 𝐋𝐢𝐧𝐮𝐱 𝐂𝐨𝐦𝐦𝐚𝐧𝐝𝐬 𝐂𝐡𝐞𝐚𝐭𝐬𝐡𝐞𝐞𝐭

• gnome-control-center : open system settings from terminal
• xclip -selection clipboard : to copy output directly to clipboard

• cat ./- (./ - stands for current directory) : cat a file with name "-"
• cat ./-filename : cat a file whose name starts with "-"
• cat \spaces \in \this \filename.txt (Original filename: spaces in this filename.txt ) - cat a file name with spaces
• base64 -d data.txt - base64 decode a file
• strings filename - output human readable text from non-humanreadable file:
• echo "acbdlksjfla KHLKJfdlsfasd" | tr 'A-Za-z' 'N-ZA-Mn-za-m' - rotate a text with all lowercase and uppercase by 13 positions:
• openssl s_client -connect <host>:<port> : connect a host with ssl encryption
• diff fileone filetwo : check difference
• tail -n <number of lines> <path & file name> : print last n lines of a file
• ln -s tmp/files/take-the-command-challenge take-the-command-challenge : Create a symbolic link named take-the-command-challenge that points to the file tmp/files/take-the-command-challenge.
• find . -delete : Delete all of the files in this challenge directory including all subdirectories and their contents.
• grep -rl 500: -r for Recursive, read all files in given directory and subdirectories & -l for Print the name of each file which contains a match.

Note: These are my notes for personal reference!

𝐁𝐚𝐬𝐢𝐜

• date : displays the current time and date

┌──(shreyas㉿kali)-[~]
└─$ date
Tuesday 04 January 2022 03:39:43 PM IST

• cal : displays a calendar of the current month

┌──(shreyas㉿kali)-[~]
└─$ cal  
    January 2022      
Su Mo Tu We Th Fr Sa  
                   1  
 2  3  4  5  6  7  8  
 9 10 11 12 13 14 15  
16 17 18 19 20 21 22  
23 24 25 26 27 28 29  
30 31                 

• df : the current amount of free space on our disk drives

┌──(shreyas㉿kali)-[~]
└─$ df  
Filesystem     1K-blocks     Used Available Use% Mounted on
udev             1953436        0   1953436   0% /dev
tmpfs             399160     1168    397992   1% /run
/dev/sda1      130538556 11247868 112613492  10% /
tmpfs            1995784        0   1995784   0% /dev/shm
tmpfs               5120        0      5120   0% /run/lock
tmpfs             399156       68    399088   1% /run/user/1000
              

• free : display the amount of free memory

┌──(shreyas㉿kali)-[~]
└─$ free                      
               total        used        free      shared  buff/cache   available
Mem:         3991568      672232     2753624        8864      565712     3079888
Swap:         998396           0      998396
            

𝐍𝐚𝐯𝐢𝐠𝐚𝐭𝐢𝐨𝐧

• pwd : print working directory

┌──(shreyas㉿kali)-[~]
└─$ pwd                
/home/shreyas
                

• cd : change directory

┌──(shreyas㉿kali)-[~]
└─$ cd practise           
                                                                                       
┌──(shreyas㉿kali)-[~/practise]
└─$ pwd
/home/shreyas/practise
                                                                                       
┌──(shreyas㉿kali)-[~/practise]
└─$ ls 
hackthebox

• cd shortcuts

• ls : List directory contents

  • ls -l: output in long format
  • ls -t: the t option to sort the result by the file’s modification time.
  • ls -lt --reverse: --reverse to reverse the order of the sort.

┌──(shreyas㉿kali)-[~]
└─$ ls
BugBounty  Documents  Music     practise  Templates
Desktop    Downloads  Pictures  Public    Videos
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ ls /usr      
bin  games  include  lib  lib32  lib64  libexec  libx32  local  sbin  share  src
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ ls practise /usr
practise:
hackthebox

/usr:
bin  games  include  lib  lib32  lib64  libexec  libx32  local  sbin  share  src
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ ls -l          
total 176
drwxr-xr-x  3 shreyas shreyas  4096 Jan  1 17:38 BugBounty
drwxr-xr-x  2 shreyas shreyas  4096 Dec 14 19:34 Desktop
drwxr-xr-x  2 shreyas shreyas  4096 Dec 14 19:34 Documents
drwxr-xr-x  3 shreyas shreyas  4096 Dec 29 15:32 Downloads
drwxr-xr-x  2 shreyas shreyas  4096 Dec 14 19:34 Music
drwxr-xr-x  2 shreyas shreyas  4096 Dec 14 19:34 Pictures
drwxr-xr-x  3 shreyas shreyas  4096 Dec 26 21:40 practise
drwxr-xr-x  2 shreyas shreyas  4096 Dec 14 19:34 Public
drwxr-xr-x  2 shreyas shreyas  4096 Dec 14 19:34 Templates
drwxr-xr-x  2 shreyas shreyas  4096 Dec 14 19:34 Videos

                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ ls -lt
total 40
drwxr-xr-x 3 shreyas shreyas 4096 Jan  1 17:38 BugBounty
drwxr-xr-x 3 shreyas shreyas 4096 Dec 29 15:32 Downloads
drwxr-xr-x 3 shreyas shreyas 4096 Dec 26 21:40 practise
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Desktop
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Documents
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Music
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Pictures
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Public
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Templates
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Videos

                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ ls -lt --reverse                                                               2 ⨯
total 40
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Videos
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Templates
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Public
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Pictures
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Music
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Documents
drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Desktop
drwxr-xr-x 3 shreyas shreyas 4096 Dec 26 21:40 practise
drwxr-xr-x 3 shreyas shreyas 4096 Dec 29 15:32 Downloads
drwxr-xr-x 3 shreyas shreyas 4096 Jan  1 17:38 BugBounty
                                                                                       

• file filename : the file command will print a brief description of the file’s contents

┌──(shreyas㉿kali)-[~/practise/hackthebox]
└─$ file flag.txt             
flag.txt: ASCII text, with no line terminators
                                                                                       
┌──(shreyas㉿kali)-[~/practise/hackthebox]
└─$ file pack.ovpn 
pack.ovpn: ASCII text

• less : allows us to scroll forward and backward through a text file.
  • Note: less is more. Means both commands are same

┌──(shreyas㉿kali)-[~/practise/hackthebox]
└─$ cat example | less
                                                                                       
┌──(shreyas㉿kali)-[~/practise/hackthebox]
└─$ less example

𝐌𝐚𝐧𝐢𝐩𝐮𝐥𝐚𝐭𝐢𝐧𝐠 𝐟𝐢𝐥𝐞𝐬 𝐚𝐧𝐝 𝐝𝐢𝐫𝐞𝐜𝐭𝐨𝐫𝐢𝐞𝐬

• Wildcards:

• List of most commonly used character classes

• Wildcard examples:

• Wildcards can be used with any command that accepts filenames as arguments

• mkdir - make directory
  • mkdir dir - single directory
  • mkdir dir1 dir2 dir3 - multiple directories

┌──(shreyas㉿kali)-[~/practise]
└─$ mkdir commandline
                                                                                       
┌──(shreyas㉿kali)-[~/practise]
└─$ ls          
commandline  hackthebox

┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ mkdir dir1 dir2 dir3
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ ls
dir1  dir2  dir3

• cp - copy files and directories
  • cp item1 item2 : copy single file item1 into item2
  • cp item... directory : copies multiple items (either files or directories) into a directory.

• mv is same as cp

• rm file : remove files and directories

• ln : create links
  • ln file link : create a hard link
  • ln -s item link : creates a symbolic link

𝐖𝐨𝐫𝐤𝐢𝐧𝐠 𝐰𝐢𝐭𝐡 𝐜𝐨𝐦𝐦𝐚𝐧𝐝𝐬

• type: is a shell builtin that displays the kind of command the shell will execute

┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ type ls      
ls is an alias for ls --color=auto
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ type ssh
ssh is /usr/bin/ssh
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ type cd 
cd is a shell builtin
                          

• which : Display an Executable’s Location

┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ which ls           
ls: aliased to ls --color=auto
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ which pwd
pwd: shell built-in command
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ which cd 
cd: shell built-in command
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ which gedit
/usr/bin/gedit
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ which firefox
/usr/bin/firefox
                       

• man : Display a Program’s Manual Page

┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ man ls         

LS(1)                               User Commands                              LS(1)

NAME
       ls - list directory contents

SYNOPSIS
       ls [OPTION]... [FILE]...

DESCRIPTION
       List  information  about  the FILEs (the current directory by default).  Sort
       entries alphabetically if none of -cftuvSUX nor --sort is specified.

       Mandatory arguments to long options are mandatory for short options too.

       -a, --all
              do not ignore entries starting with .

       -A, --almost-all
              do not list implied . and ..

       --author
              with -l, print the author of each file

 Manual page ls(1) line 1 (press h for help or q to quit)

• apropos - Display Appropriate Commands

┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ apropos copy            
cifsdd (8)           - convert and copy a file over SMB
COPY (7)             - copy data between a file and a table
cp (1)               - copy files and directories
cpgr (8)             - copy with locking the given file to the password or group file
cpio (1)             - copy files to and from archives
cppw (8)             - copy with locking the given file to the password or group file
dd (1)               - convert and copy a file
debconf-copydb (1)   - copy a debconf database
git-checkout-index (1) - Copy files from the index to the working tree
gvfs-copy (1)        - Deprecated equivalent of gio copy
install (1)          - copy files and set attributes
mariadb-hotcopy (1)  - a database backup program
mysqlhotcopy (1)     - a database backup program
ntfscp (8)           - copy file to an NTFS volume.
objcopy (1)          - copy and translate object files
ptrepack (1)         - Copy any PyTables Leaf, Group or complete subtree into anothe...
rcp (1)              - OpenSSH secure file copy
rsync (1)            - a fast, versatile, remote (and local) file-copying tool
scp (1)              - OpenSSH secure file copy
ssh-copy-id (1)      - use locally available keys to authorise logins on a remote ma...
svnversion (1)       - Produce a compact version identifier for a working copy.
vfs_shadow_copy (8)  - Expose snapshots to Windows clients as shadow copies.
vfs_shadow_copy2 (8) - Expose snapshots to Windows clients as shadow copies.
x86_64-linux-gnu-objcopy (1) - copy and translate object files
                                                                                       

• whatis : Display One-line Manual Page Descriptions

┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ whatis rm    
rm (1)               - remove files or directories
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ whatis ls
ls (1)               - list directory contents
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ whatis sudo
sudo (8)             - execute a command as another user
                            

• info : Display a Program’s Info Entry

                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ info ls

Next: dir invocation,  Up: Directory listing

10.1 ‘ls’: List directory contents
==================================

The ‘ls’ program lists information about files (of any type, including
directories).  Options and file arguments can be intermixed arbitrarily,
as usual.

   For non-option command-line arguments that are directories, by
default ‘ls’ lists the contents of directories, not recursively, and
omitting files with names beginning with ‘.’.  For other non-option
arguments, by default ‘ls’ lists just the file name.  If no non-option
argument is specified, ‘ls’ operates on the current directory, acting as
if it had been invoked with a single argument of ‘.’.

   By default, the output is sorted alphabetically, according to the
locale settings in effect.(1)  If standard output is a terminal, the
output is in columns (sorted vertically) and control characters are
output as question marks; otherwise, the output is listed one per line
and control characters are output as-is.

-----Info: (coreutils)ls invocation, 56 lines --Top------------------------------------
Follow xref: gument is specified, ‘ls’ operates on the current directory, acting asif 

• alias : Creating Our Own Commands with alias
  • trick: It’s possible to put more than one command on a line by separating each command with a semicolon
  • command1; command2; command3...

[me@linuxbox ~]$ cd /usr; ls; cd -
bin  games  include  lib  local  sbin  share  src
/home/me
[me@linuxbox ~]$

[me@linuxbox ~]$ type foo
bash: type: foo: not found

[me@linuxbox ~]$ alias foo='cd /usr; ls; cd -'
[me@linuxbox ~]$ foo
bin  games  include  lib  local  sbin  share  src
/home/me
[me@linuxbox ~]$
[me@linuxbox ~]$ type foo
foo is aliased to `cd /usr; ls; cd -'

[me@linuxbox ~]$ unalias foo
[me@linuxbox ~]$ type foo
bash: type: foo: not found

𝐑𝐞𝐝𝐢𝐫𝐞𝐜𝐭𝐢𝐨𝐧

• <command> > <file> : Redirecting Standard Output

┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ ls -l /usr/bin > ls-output.txt
                                                                                       
┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ ls -l                         
total 180
drwxr-xr-x 2 shreyas shreyas   4096 Jan  4 17:21 dir1
drwxr-xr-x 2 shreyas shreyas   4096 Jan  4 17:21 dir2
drwxr-xr-x 2 shreyas shreyas   4096 Jan  4 17:21 dir3
-rw-r--r-- 1 shreyas shreyas 171639 Jan  4 18:21 ls-output.txt
                                                                   

• command >> file - append redirected output to a file instead of overwriting the file

[me@linuxbox ~]$ ls -l /usr/bin >> ls-output.txt

• 0> OR < : redirecting standard input
• > : redirecting standard output
• 2> : redirecting standard error

[me@linuxbox ~]$ ls -l /bin/usr 2> ls-error.txt

• ls -l /bin/usr > ls-output.txt 2>&1 OR ls -l /bin/usr &> ls-output.txt: Redirecting Standard Output and Standard Error to One File
• ls -l /bin/usr 2> /dev/null : Disposing unwanted output

• command1 | command2 : Pipeline
• wc : Print line, Word, and Byte counts
• grep : print line matching pattern
• head -n <number of lines> ls-output.txt : print initial lines of file
• tail -n <number of lines> ls-output.txt : print last lines of files
• tee : Read from Stdin and Output to Stdout and Files

┌──(shreyas㉿kali)-[~/practise/commandline]
└─$ wc ls-output.txt 
  2557  24294 171639 ls-output.txt

[me@linuxbox ~]$ head -n 5 ls-output.txt
total 343496
-rwxr-xr-x 1 root root       31316 2017-12-05 08:58 [
-rwxr-xr-x 1 root root        8240 2017-12-09 13:39 411toppm
-rwxr-xr-x 1 root root      111276 2017-11-26 14:27 a2p
-rwxr-xr-x 1 root root       25368 2016-10-06 20:16 a52dec
[me@linuxbox ~]$ tail -n 5 ls-output.txt
-rwxr-xr-x 1 root root        5234 2017-06-27 10:56 znew
-rwxr-xr-x 1 root root         691 2015-09-10 04:21 zonetab2pot.py
-rw-r--r-- 1 root root         930 2017-11-01 12:23 zonetab2pot.pyc
-rw-r--r-- 1 root root         930 2017-11-01 12:23 zonetab2pot.pyo
lrwxrwxrwx 1 root root           6 2016-01-31 05:22 zsoelim -> soelim

𝐒𝐞𝐞𝐢𝐧𝐠 𝐭𝐡𝐞 𝐰𝐨𝐫𝐥𝐝 𝐚𝐬 𝐭𝐡𝐞 𝐬𝐡𝐞𝐥𝐥 𝐬𝐞𝐞𝐬 𝐢𝐭

• echo : Display a line of text
  • echo * : works same as ls
  • echo D* : Display files/directories which starts with D
  • echo *s : Display files/drectories which ends with s
  • echo [[:upper:]]* : Display files/directories that starts with uppercase letters
  • echo /usr/*/share : display all directories between /usr/ & /share
  • echo ~ : tilde expansion

┌──(shreyas㉿kali)-[~]
└─$ echo hello there my name is shreyas                       
hello there my name is shreyas
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ echo *                             
BugBounty Desktop Documents Downloads Music Pictures practise Public Templates Videos
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ echo D*
Desktop Documents Downloads
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ echo *s
Documents Downloads Pictures Templates Videos
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ echo [[:upper:]]*
BugBounty Desktop Documents Downloads Music Pictures Public Templates Videos
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ echo /usr/*/share
/usr/local/share
                                                                                      
┌──(shreyas㉿kali)-[~]
└─$ echo ~           
/home/shreyas

                                                                                       

• Arithmetic Expansion:
  • $((expression))

┌──(shreyas㉿kali)-[~]
└─$ echo $((2 + 2))
4

┌──(shreyas㉿kali)-[~]
└─$ echo $(($((5**2)) * 3))
75
      

• Brace Expansion: create multiple text strings from a pattern containing braces

┌──(shreyas㉿kali)-[~]
└─$ echo Front-{A,B,C}-Back
Front-A-Back Front-B-Back Front-C-Back
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$  echo Number_{1..5}
Number_1 Number_2 Number_3 Number_4 Number_5
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ echo {01..15}
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15
                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ echo a{A{1,2},B{3,4}}b
aA1b aA2b aB3b aB4b
                                                   

• Parameter expansion: echo $var
• Command Substitution
  • echo $(ls)
  • ls -l $(which cp)
  • file $(ls -d /usr/bin/* | grep zip)

• Quoting:
  • Double Quotes: If we place text inside double quotes, all the special characters used by the shell lose their special meaning and are treated as ordinary characters. The exceptions are $ (dollar sign), \ (backslash), and ` (backtick).
  • Single Quotes: If we need to suppress all expansions, we use single quotes.
• Escaping Characters:
  • \ : is used for escaping
• Backslash Escape Situation:

┌──(shreyas㉿kali)-[~]
└─$ sleep 10; echo -e "Time's up\a"
Time's up
           

𝐀𝐝𝐯𝐚𝐧𝐜𝐞𝐝 𝐊𝐞𝐲𝐛𝐨𝐚𝐫𝐝 𝐓𝐫𝐢𝐜𝐤𝐬

• clear : Clear the terminal screen

• history : Display or manipulate the history list

• Cursor Movement:

• Modifying Text

• History Expansion

𝐏𝐞𝐫𝐦𝐢𝐬𝐬𝐢𝐨𝐧𝐬

• id : Display user identity

• chmod : Change a file’s mode

• umask : Set the default file permissions

• su : Run a shell as another user

• sudo : Execute a command as another user

• chown: Change a file’s owner

• chgrp: Change a file’s group ownership

• passwd: Change a user’s password

• Permission attribute Examples:

• chmod : Change File Mode
  • 6(rw-)
  • 7(rwx)
  • 5(r-x)
  • 4(r--)
  • 0(---)

• If no character is specified, “all” will be assumed. The operation may be a + indicating that a permission is to be added, a - indicating that a permission is to be taken away, or a = indicating that only the specified permissions are to be applied and that all others are to be removed.

𝐏𝐫𝐨𝐜𝐞𝐬𝐬𝐞𝐬

• ps : Report a snapshot of current processes
• top : Display tasks
• jobs : List active jobs
• bg : Place a job in the background
• fg : Place a job in the foreground
• kill : Send a signal to a process
• killall : Kill process by name
• shutdown : Shut down or reboot the system

𝐍𝐞𝐭𝐰𝐨𝐫𝐤𝐢𝐧𝐠

• ping : Checks if a network is reachable, ping command sends a special network packet called an ICMP ECHO_REQUEST to a specified host. Most network devices receiving this packet will reply to it, allowing the network connection to be verified.

┌──(shreyas㉿kali)-[~]
└─$ ping youtube.com   
PING youtube.com (142.250.204.46) 56(84) bytes of data.
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=1 ttl=128 time=149 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=2 ttl=128 time=151 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=3 ttl=128 time=188 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=4 ttl=128 time=140 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=5 ttl=128 time=139 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=6 ttl=128 time=120 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=7 ttl=128 time=131 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=8 ttl=128 time=148 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=9 ttl=128 time=137 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=10 ttl=128 time=132 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=11 ttl=128 time=144 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=12 ttl=128 time=128 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=13 ttl=128 time=128 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=14 ttl=128 time=141 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=15 ttl=128 time=135 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=16 ttl=128 time=130 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=17 ttl=128 time=133 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=18 ttl=128 time=142 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=19 ttl=128 time=134 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=20 ttl=128 time=137 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=21 ttl=128 time=139 ms
^C64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=22 ttl=128 time=140 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=23 ttl=128 time=121 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=24 ttl=128 time=146 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=25 ttl=128 time=136 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=26 ttl=128 time=165 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=27 ttl=128 time=176 ms
64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=28 ttl=128 time=132 ms
^C
--- youtube.com ping statistics ---
28 packets transmitted, 28 received, 0% packet loss, time 27045ms
rtt min/avg/max/mdev = 120.372/140.817/187.758/14.526 ms
                                                                    

• traceroute : lists all the “hops” network traffic takes to get from the local system to a specified host.

┌──(shreyas㉿kali)-[~]
└─$ traceroute google.com
traceroute to google.com (142.250.204.110), 30 hops max, 60 byte packets
 1  192.168.29.2 (192.168.29.2)  0.227 ms  0.099 ms  0.175 ms
 2  * * *
 3  * * *
 4  * * *
 5  * * *
 6  * * *
 7  * * *
 8  * * *
 9  * * *
10  * * *
11  * * *
12  * * *
13  * * *

• ip a : It replaces the earlier and now deprecated ifconfig program.

┌──(shreyas㉿kali)-[~]
└─$ ip a    
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:c5:88:a0 brd ff:ff:ff:ff:ff:ff
    inet 192.168.x.x/24 brd 192.168.x.x scope global dynamic noprefixroute eth0
       valid_lft 1630sec preferred_lft 1630sec
    inet6 fe80::20c:29ff:x:x/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

• netstat : The netstat program is used to examine various network settings and statistics.
  • -r option will display the kernel’s network routing table
  • ie : we can examine the network interfaces in our system

┌──(shreyas㉿kali)-[~]
└─$ netstat -ie                   
Kernel Interface table
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.x.x  netmask 255.255.255.0  broadcast 192.168.29.255
        inet6 fe80::20c:29ff:x:x  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:c5:88:a0  txqueuelen 1000  (Ethernet)
        RX packets 102  bytes 11285 (11.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 207  bytes 17053 (16.6 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 8  bytes 400 (400.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 8  bytes 400 (400.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        
                                                                                                       
┌──(shreyas㉿kali)-[~]
└─$ netstat -r 
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
default         192.168.29.2    0.0.0.0         UG        0 0          0 eth0
192.168.29.0    0.0.0.0         255.255.255.0   U         0 0          0 eth0

Transporting Files over a Network

• ftp : ftp is used to communicate with FTP servers, machines that contain files that can be uploaded and downloaded over a network. FTP (in its original form) is not secure because it sends account names and passwords in cleartext.

[me@linuxbox ~]$ ftp fileserver
Connected to fileserver.localdomain.
220 (vsFTPd 2.0.1)
Name (fileserver:me): anonymous
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> cd pub/cd_images/ubuntu-18.04
250 Directory successfully changed.
ftp> ls
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
-rw-rw-r--    1 500      500      733079552 Apr 25 03:53 ubuntu-18.04-desktop-amd64.iso
226 Directory send OK.
ftp> lcd Desktop
Local directory now /home/me/Desktop
ftp> get ubuntu-18.04-desktop-amd64.iso
local: ubuntu-18.04-desktop-amd64.iso remote: ubuntu-18.04-desktop-amd64.iso
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for ubuntu-18.04-desktop-amd64.iso (733079552 bytes).
226 File send OK.
733079552 bytes received in 68.56 secs (10441.5 kB/s)
ftp> bye

• lftp is a Better ftp

• wget : It is useful for downloading content from both web and FTP sites. Single files, multiple files, and even entire sites can be downloaded.

[me@linuxbox ~]$ wget http://linuxcommand.org/index.php
--11:02:51--  http://linuxcommand.org/index.php
           => `index.php'
Resolving linuxcommand.org... 66.35.250.210
Connecting to linuxcommand.org|66.35.250.210|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]

    [ <=>                                 ] 3,120         --.--K/s

11:02:51 (161.75 MB/s) - `index.php' saved [3120]

• ssh : SSH solves the two basic problems of secure communication with a remote host.
  • It authenticates that the remote host is who it says it is (thus preventing so-called man-in-the-middle attacks).
  • It encrypts all of the communications between the local and remote hosts.
  • ssh remote-sys : To connect to a remote host named remote-sys
  • ssh username@remote-sys : login with specific username
  • ssh remote-sys <command>: to execute just a single command

[me@linuxbox ~]$ ssh remote-sys
The authenticity of host 'remote-sys (192.168.1.4)' can't be established.
RSA key fingerprint is 41:ed:7a:df:23:19:bf:3c:a5:17:bc:61:b3:7f:d9:bb.
Are you sure you want to continue connecting (yes/no)?

• scp - (secure copy). copy files from local host to remote host

[me@linuxbox ~]$ scp remote-sys:document.txt .
me@remote-sys's password:
document.txt                           100% 5581     5.5KB/s   00:00
[me@linuxbox ~]$

• sftp : SSH file-copying program

[me@linuxbox ~]$ sftp remote-sys
Connecting to remote-sys...
me@remote-sys's password:
sftp> ls
ubuntu-8.04-desktop-i386.iso
sftp> lcd Desktop
sftp> get ubuntu-8.04-desktop-i386.iso
Fetching /home/me/ubuntu-8.04-desktop-i386.iso to ubuntu-8.04-desktop-i386.iso
/home/me/ubuntu-8.04-desktop-i386.iso 100%  699MB   7.4MB/s   01:35
sftp> bye

𝐒𝐞𝐚𝐫𝐜𝐡𝐢𝐧𝐠 𝐟𝐨𝐫 𝐟𝐢𝐥𝐞𝐬

• locate : Find files by name
• find : Search for files in a directory hierarchy
• xargs : Build and execute command lines from standard input
• touch : Change file times
• stat: Display file or file system status

• find : find files the hard way
  • find ~ : to produce a listing of our home directory
  • find ~ | wc -l : to count the number of files.
  • find ~ -type d | wc -l : -type d limit the search to directories
  • find ~ -type f | wc -l : -type f limit the search to regular files
  • find ~ -type f -name "*.JPG" -size +1M | wc -l: all the regular files that match the wildcard pattern *.JPG and are larger than one megabyte

• find size units

• More about find options: Find cheatsheet

• xargs - It accepts input from standard input and converts it into an argument list for a specified command

find ~ -type f -name 'foo*' -print | xargs ls -l
-rwxr-xr-x 1 me   me 224 2007-10-29 18:44 /home/me/bin/foo
-rw-r--r-- 1 me   me   0 2016-09-19 12:53 /home/me/foo.txt

Remaining:

• archiving and backup
• regular expressions
• text processing
• compiling programs
• that's enough for now i guess