#### commands info
man ls # manual and all "ls" info
whatis ls # quit description for what is ls
apropos list # search what tool to do this function
whoami
sudo adduser mohamed # add user
usermod -aG sudo mohamed # add sudo user
shasum file # see file hashing
### file mangement 1-ordinary files 2- special files 3-directories
pwd # current directory
ls # list
ls -l # with all informations
ll
ls -il
ls -a # with all hidden files
ls -i # inode number of files (index of file)
find /home/boyka -inum 1150561 #find file with inode number
### creating files
cat>file_name # Create a file and enter data and ctrl+D to save the file
cat file_name # display the file data
touch file_name2 # create and save empty file
### move - rename - copy - delete
mv file_name file_name_new # rename a file or move the file
mv file_name /home/boyka/Desktop
mv * /home/boyka/Desktop # use regex to selet more than file to move
mv f* /home/boyka/Desktop
mv /home/boyka/Desktop/file_name . # . mean the final same location of the file
cp file_name /home/boyka/Desktop # copy
cp file_name /home/boyka/Desktop/file_name_new # copy with new name
rm file_name file_name2 # delete specific files
rm * # delete all files
### display files
cat file_name # dispay file data
wc file_name # display (n1 n2 n3 file_name) its count (line_num words_num char._num)
wc -l file_name # number of lines
wc -w file_name # number of words
wc -c file_name # number of char.
### standard linux streams (this built-in files work when we creating script or program)
stdin # (0) this file take the input
stdout # (1) giving the output
stderr # (2) work and detect errors
### directory mangement [hidden files get crated by defalult when create directory { (.)-the informations of current dir (..)-the information of level above dir }]
cd # change directory
cd .. # step back
mkdir # make directory
mkdir boyka\ tasks # \ to make directory with space separate name (boyka tasks)
ls -la # show detail informations with hidden files/directories
mv -r
cp -r
### permissions [ owner - group - other ] >>( read - write - execute )
# [file/dir|owner|group|other]
-rwxr-xr-x # [-] file
drwxr-xr-- # [d] dir
# change with symbolic method [u: user / g: group / o:others]
chmod u+x file_name # add permission to user
chmod u-wx file_name # remove permission from user
chmod u=rwx file_name # set the permissions of user
chmod u+x,g-w,o=r file_name
chmod a=rwx file_name # set for all (u,g and o)
# with octal mehod [0:--- , 1:--x , 2:-w- , 3:2+1 , 4:r-- , 5:4+1 , 6:4+2 , 7:4+2+1]
chmod 775 file_name # 7 for user , 6 for group and 5 for other
umask # (0002) get the number that represent the default permissions for new files or dir created [7777-umask=permissions_num]
umask 027 # change umask number [7777-7027=0750] umask_new=0750
### Environment Variables
env # show the default variables declars in the environment
env boyka="kshckhdjoj" # declare my own env. variable
.profile # the file that run automaticaly when you start .... if it contains nothing the system skiped it and go to home directory
.bash_history # bash comands history
.bash_logout # log out task
### Basic Utilities ( printing - sending a mail)
# mails in localhost >> var/spool/mail
pr option(s) file(s) # ex: pr -2 file | more >> this will make two colomns
lpr file # send to printer
$ mail -s “Enter the subject” user1@domain.com
$ mail -s “The Subject” user1@domain.com < /root/testemail.txt # Send message from a file
$ echo “THIS IS A TEST EMAIL” | mail -s “Enter the subject” user1@domain.com
$ echo “THIS IS A TEST EMAIL” | mail -s “Enter the subject” user1@domain.com,user2@domain.com # Multiple recipients
$ echo “THIS IS A TEST EMAIL” | mail -s “Enter the subject” -c user1@domain.com,user2@domain.com # CC and BCC
$ echo “THIS IS A TEST EMAIL” | mail -s “Enter the subject” –r “Tom<tom@gmail.com>” user1@domain.com # Specify From name and address
# Specify “Reply-To” address
$ echo “THIS IS A TEST EMAIL” | mail -s “Enter the subject” replyto= tom@gmail.com user1@domain.com
$ echo “THIS IS A TEST EMAIL” | mail -s “Enter the subject” replyto= “Tomtom@gmail.com” user1@domain.com
# Attachments
The option –a is used to add an attachment along with the email.
$ echo “THIS IS A TEST EMAIL” | mail -s “Enter the subject” –r “Tom<tom@gmail.com>” –a /path/to/file user1@domain.com
### pipes and filters
# pipe >>>> A pipe is a means by which the output from one process becomes the input to a second. In technical terms,
# the standard output (stout) of one command is sent to the standard input (stdin) of a second command
command_1 | command_2 | command_3 | .... | command_N
$ ls -l | more # list and get the --more-- option == { ls -l > temp , more < temp , rm temp}
$ sort record.txt | uniq # This will sort the given file and print the unique values only
$ cat sample2.txt | head -7 | tail -5 # select first 7 lines and last 5 lines from the file and print those lines which are common to both of them
$ ls -l | find ./ -type f -name "*.txt" -exec grep "program" {} \; # select files with .txt extension in the given directory
# and search for pattern like “program” in the above example and print those ine which have program in them
$ cat result.txt | grep "Rajat Dua" | tee file2.txt | wc -l # select Rajat Dua and store them in file2.txt and print total number of lines matching Rajat Dua
# filter >>>> A pipe can pass the standard output of one operation to the standard input of another,
# but a filter can modify the stream. A filter takes the standard input, does something useful with it,
# and then returns it as a standard output. Linux has a large number of filters.
# Some useful ones are the commands awk, grep, sed, spell, and wc.
head -n # Show the first n lines.
tail -n # Show the last n lines.
sort # Sort lines in a given way [sort -n file , sort -r file , sort -nr , sort -f ].
wc # How many words, characters and lines.
grep # Search for a given pattern.
### File editors [ ex. : gedit - nano - vi,vim ]
ifconfig
#to check connectivity between my machine and any ip
ping www.google.com #or by ip
# the resolution between every MAC and IP
arp #Address Resolution Protocol
# to connect to file server (up and down files)
ftp #File Transfer Protocol
> open ftp.microsoft.com # entry with usr name and password
> bye # for exit
#for get IP address for any site
nslookup
> www.google.com
Server: 192.168.1.1
Address: 192.168.1.1#53
Non-authoritative answer:
Name: www.google.com
Address: 172.217.18.36
> exit
#to recognize the routing table components of my device
route
# show all my device connections
netstate
# to scan ports
nmap 127.0.0.1
nmap -p 1-65535 127.0.0.1 # -p to choose a range
nmap -p 1-65535 -m 10 127.0.0.1 # -m to issues several prob requests at the same time
# Scanning Multiple Hosts
nmap host1 host2 host3 # by names or ip
nmap 192.168.1.* # warning: never try to scan *.*.*.* on any machine connected to the Internet
nmap 192.168.1.0/24 # by CIDR notation
# scanning ranges
nmap 192.168.1.10-35
nmap 192.168.1,2,3,4.10
nmap 192.168.1,2.3,4.10-35
# nmap flags and options
-sT Perform a full open TCP scan
-sS Perform a SYN (stealth) TCP scan
-sU Perform a UDP scan
-sR or -sV Perform an RPC service scan (should be used in conjunction with another scan type)
-A aggressive scan for more info
-O Try remote OS detection
-O --osscan-guess guess the OS if not detected
-P0 Donít try to see if a host is up before scanning it
-p <port range> Specify a range of ports to scan
-M <max connections> The maximum number of parallel connection attempts to make at one time. For LANs, should be no more than 18. For slow links (WAN, Internet), this can be significantly higher.
# to capture and analyze network traffic going through your system and for troubleshooting
tcpdump
-x # display all packet in hex
-s 1500 # snap length ,1500 byte,if 0 means show all packet
-w file # to write in file
-r file
B0YK4
Cyber Security blog and CTFs writeups