InternetServicesBook/README.md

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    <img src="https://github.com/trimstray/awesome-ninja-admins/blob/master/doc/img/awesome_ninja_admins.png"
        alt="Master">
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<br>

<h4 align="center">A collection of awesome lists, manuals, blogs, hacks, one-liners and tools for <b>Awesome Ninja Admins</b>.</h4>

<br>

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  <a href="https://github.com/trimstray/awesome-ninja-admins/tree/master">
    <img src="https://img.shields.io/badge/Branch-master-green.svg?longCache=true"
        alt="Branch">
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        alt="Awesome">
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        alt="License">
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<div align="center">
  <sub>Created by
  <a href="https://twitter.com/trimstray">trimstray</a> and
  <a href="https://github.com/trimstray/awesome-ninja-admins/graphs/contributors">
    contributors
  </a>
</div>

<br>

***

## Who is Ninja Admins?

- race of pure evil who rule the network through a monarchistic feudelic system
- they never opened the door for strangers (or anyone at all)
- they know very nasty piece of code like a **[fork bombs](https://en.wikipedia.org/wiki/Fork_bomb)**
- they can make dd is not a **[destroyer of disks](http://www.noah.org/wiki/Dd_-_Destroyer_of_Disks)**
- they know that `#!/usr/bin/env bash` superior to `#!/bin/bash`
- they know that `su -` logs in completely as root
- they miss and cry for **[Slackware](http://www.slackware.com/)** on production
- they love the old admin nix-world

## :ballot_box_with_check: Todo

- [ ] Add useful shell functions
- [ ] Add one-liners for collection tools (eg. CLI Tools)
- [ ] Add Ninja Admins T-Shirt stickers
- [ ] Generate Awesome Ninja Admins book (eg. pdf format)

## Ninja Admins Collection

#### CLI Tools

##### :black_small_square: Shells

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://ohmyz.sh/"><b>Oh My ZSH!</b></a> - the best framework for managing your Zsh configuration.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/Bash-it/bash-it"><b>bash-it</b></a> - a community Bash framework.<br>
</p>

##### :black_small_square: Managers

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://midnight-commander.org/"><b>Midnight Commander</b></a> - visual file manager, licensed under GNU General Public License.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.gnu.org/software/screen/"><b>screen</b></a> - full-screen window manager that multiplexes a physical terminal.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/tmux/tmux/wiki"><b>tmux</b></a> - terminal multiplexer, lets you switch easily between several programs in one terminal.<br>
</p>

##### :black_small_square: Network

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://curl.haxx.se/"><b>Curl</b></a> - command line tool and library
for transferring data with URLs.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/jkbrzt/httpie"><b>HTTPie</b></a> - a user-friendly HTTP client.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://gnutls.org/manual/html_node/gnutls_002dcli-Invocation.html"><b>gnutls-cli</b></a> - client program to set up a TLS connection to some other computer.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://netcat.sourceforge.net/"><b>netcat</b></a> - networking utility which reads and writes data across network connections, using the TCP/IP protocol.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.tcpdump.org/"><b>tcpdump</b></a> - powerful command-line packet analyzer.<br>
</p>

##### :black_small_square: Databases

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/dbcli/pgcli"><b>pgcli</b></a> - postgres CLI with autocompletion and syntax highlighting.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/dbcli/mycli"><b>mycli</b></a> - terminal client for MySQL with autocompletion and syntax highlighting.<br>
</p>

#### Web Tools

##### :black_small_square: SSL

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.ssllabs.com/ssltest/"><b>SSL Server Test</b></a> - free online service performs a deep analysis of the configuration of any SSL web server.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://dev.ssllabs.com/ssltest/"><b>SSL Server Test (DEV)</b></a> - free online service performs a deep analysis of the configuration of any SSL web server.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.htbridge.com/ssl/"><b>ImmuniWeb® SSLScan</b></a> - test SSL/TLS (PCI DSS, HIPAA and NIST).<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://report-uri.com/home/tools"><b>Report URI</b></a> - monitoring security policies like CSP and HPKP.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://csp-evaluator.withgoogle.com/"><b>CSP Evaluator</b></a> - allows developers and security experts to check if a Content Security Policy.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://ccadb.org/resources"><b>Common CA Database</b></a> - repository of information about CAs, and their root and intermediate certificates.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://certstream.calidog.io/"><b>CERTSTREAM</b></a> - real-time certificate transparency log update stream.<br>
</p>

##### :black_small_square: HTTP Headers

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://securityheaders.com/"><b>Security Headers</b></a> - analyse the HTTP response headers (with rating system to the results).<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://observatory.mozilla.org/"><b>Observatory by Mozilla</b></a> - set of tools to analyze your website.<br>
</p>

##### :black_small_square: DNS

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://viewdns.info/"><b>ViewDNS</b></a> - one source for free DNS related tools and information.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://dnsspy.io/"><b>DNS Spy</b></a> - monitor, validate and verify your DNS configurations.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://dnslytics.com/"><b>DNSlytics</b></a> - online investigation tool.<br>
</p>

##### :black_small_square: Mail

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://mxtoolbox.com/SuperTool.aspx"><b>MX Toolbox</b></a> - all of your MX record, DNS, blacklist and SMTP diagnostics in one integrated tool.<br>
</p>

##### :black_small_square: Mass scanners (search engines)

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://censys.io/"><b>Censys</b></a> - platform that helps information security practitioners discover, monitor, and analyze devices.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.shodan.io/"><b>Shodan</b></a> - the world's first search engine for Internet-connected devices.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://viz.greynoise.io/table"><b>GreyNoise</b></a> - mass scanner (such as Shodan and Censys).<br>
</p>

##### :black_small_square: Net-tools

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://toolbar.netcraft.com/site_report"><b>Netcraft</b></a> -  detailed report about the site, helping you to make informed choices about their integrity.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://securitytrails.com/"><b>Security Trails</b></a> - APIs for Security Companies, Researchers and Teams.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://tools.keycdn.com/curl"><b>Online Curl</b></a> - curl test, analyze HTTP Response Headers.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://ping.eu/"><b>Ping.eu</b></a> - online Ping, Traceroute, DNS lookup, WHOIS and others.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://network-tools.com/"><b>Network-Tools</b></a> - network tools for webmasters, IT technicians & geeks.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.url-encode-decode.com/"><b>URL Encode/Decode</b></a> - tool from above to either encode or decode a string of text.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.hardenize.com/"><b>Hardenize</b></a> - deploy the security standards.<br>
</p>

##### :black_small_square: Performance

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://gtmetrix.com/"><b>GTmetrix</b></a> - analyze your site’s speed and make it faster.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://performance.sucuri.net/"><b>Sucuri loadtimetester</b></a> - test here the
performance of any of your sites from across the globe.<br>
</p>

##### :black_small_square: Passwords

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.random.org/passwords/"><b>Random.org</b></a> - generate random passwords.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://gotcha.pw/"><b>Gotcha?</b></a> - list of 1.4 billion accounts circulates around the Internet.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://haveibeenpwned.com/"><b>have i been pwned?</b></a> - check if you have an account that has been compromised in a data breach.<br>
</p>

#### Manuals/Howtos/Tutorials

##### :black_small_square: Bash

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/dylanaraps/pure-bash-bible"><b>pure-bash-bible</b></a> - a collection of pure bash alternatives to external processes.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://wiki.bash-hackers.org/start"><b>The Bash Hackers Wiki</b></a> - hold documentation of any kind about GNU Bash.<br>
</p>

##### :black_small_square: Unix tutorials

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.cyberciti.biz/"><b>nixCraft</b></a> - linux and unix tutorials for new and seasoned sysadmin.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.tecmint.com/"><b>TecMint</b></a> - the ideal Linux blog for Sysadmins & Geeks.<br>
</p>

##### :black_small_square: Hacking

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://www.hackingarticles.in/"><b>Hacking Articles</b></a> - LRaj Chandel's Security & Hacking Blog.<br>
</p>

#### Blogs

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://www.brendangregg.com/"><b>Brendan Gregg's Blog</b></a> - Brendan Gregg is an industry expert in computing performance and cloud computing.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://gynvael.coldwind.pl/"><b>Gynvael "GynDream" Coldwind</b></a> - Gynvael is a IT security engineer at Google.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://lcamtuf.coredump.cx/"><b>Michał "lcamtuf" Zalewski</b></a> - "white hat" hacker, computer security expert.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://ma.ttias.be/"><b>Mattias Geniar</b></a> - developer, Sysadmin, Blogger, Podcaster and Public Speaker.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://nickcraver.com/"><b>Nick Craver</b></a> - Software Developer and Systems Administrator for Stack Exchange.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://robert.penz.name/"><b>Robert Penz</b></a> - IT security Expert.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://scotthelme.co.uk/"><b>Scott Helme</b></a> - Security Researcher, international speaker and founder of securityheaders.com and report-uri.com.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://security.szurek.pl/"><b>Kacper Szurek</b></a> - Detection Engineer at ESET.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.troyhunt.com/"><b>Troy Hunt</b></a> -  Microsoft Regional Director and Microsoft Most Valuable Professional for Developer Security.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://linux-audit.com/"><b>Linux Audit</b></a> - the Linux security blog about Auditing, Hardening, and Compliance by Michael Boelen.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://www.grymoire.com/"><b>The Grymoire</b></a> - collection of useful incantations for wizards, be you computer wizards, magicians, or whatever.<br>
</p>

#### Systems/Services

##### :black_small_square: Systems

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://www.slackware.com/"><b>Slackware</b></a> - the most "Unix-like" Linux distribution.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.openbsd.org/"><b>OpenBSD</b></a> - multi-platform 4.4BSD-based UNIX-like operating system.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://hardenedbsd.org/"><b>HardenedBSD</b></a> - HardenedBSD aims to implement innovative exploit mitigation and security solutions.<br>
</p>

##### :black_small_square: HTTP(s) Services

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://varnish-cache.org/"><b>Varnish HTTP Cache</b></a> - HTTP accelerator designed for content-heavy dynamic web sites.<br>
</p>

##### :black_small_square: Security/hardening

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://emeraldonion.org/"><b>Emerald Onion</b></a> - Seattle-based encrypted-transit internet service provider.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.unbound.net/"><b>unbound</b></a> - validating, recursive, and caching DNS resolver (with TLS).<br>
</p>

#### Lists

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/kahun/awesome-sysadmin"><b>Awesome Sysadmin</b></a> - amazingly awesome open source sysadmin resources.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/alebcay/awesome-shell"><b>Awesome Shell</b></a> - awesome command-line frameworks, toolkits, guides and gizmos.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/Hack-with-Github/Awesome-Hacking"><b>Awesome-Hacking</b></a> - awesome lists for hackers, pentesters and security researchers.<br>
</p>

#### Hacking/Penetration testing

##### :black_small_square: Bounty programs

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.openbugbounty.org/"><b>Openbugbounty</b></a> - allows any security researcher reporting a vulnerability on any website.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.hackerone.com/"><b>hackerone</b></a> - global hacker community to surface the most relevant security issues.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.bugcrowd.com/"><b>bugcrowd</b></a> - crowdsourced cybersecurity for the enterprise.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://crowdshield.com/"><b>Crowdshield</b></a> - crowdsourced Security & Bug Bounty Management.<br>
</p>

##### :black_small_square: Web Training Apps

<p>
&nbsp;&nbsp;:small_orange_diamond: <a href="http://www.dvwa.co.uk/"><b>DVWA</b></a> - PHP/MySQL web application that is damn vulnerable.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://sourceforge.net/projects/mutillidae/"><b>OWASP Mutillidae II</b></a> - free, open source, deliberately vulnerable web-application.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.owasp.org/index.php/OWASP_Juice_Shop_Project"><b>OWASP Juice Shop Project</b></a> - the most bug-free vulnerable application in existence.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://www.owasp.org/index.php/Category:OWASP_WebGoat_Project"><b>OWASP WebGoat Project</b></a> - insecure web application maintained by OWASP designed to teach web app security.<br>
&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/opendns/Security_Ninjas_AppSec_Training"><b>Security Ninjas</b></a> - open source application security training program.<br>
</p>

#### One-liners

##### Table of Contents

- **[System](#system)**
  * [terminal](#tool-terminal)
  * [mount](#tool-mount)
  * [fuser](#tool-fuser)
  * [ps](#tool-ps)
  * [top](#tool-top)
  * [find](#tool-find)
  * [diff](#tool-diff)
  * [tail](#tool-tail)
  * [cpulimit](#tool-cpulimit)
  * [pwdx](#tool-pwdx)
  * [tr](#tool-tr)
  * [chmod](#tool-chmod)
  * [who](#tool-who)
  * [screen](#tool-screen)
  * [du](#tool-du)
  * [inotifywait](#tool-inotifywait)
  * [openssl](#tool-openssl)
- **[HTTP/HTTPS](#http-https)**
  * [curl](#tool-curl)
  * [httpie](#tool-httpie)
- **[Network](#network)**
  * [ssh](#tool-ssh)
  * [linux-dev](#tool-linux-dev)
  * [tcpdump](#tool-tcpdump)
  * [ngrep](#tool-ngrep)
  * [hping3](#tool-hping3)
  * [netcat](#tool-netcat)
  * [socat](#tool-socat)
  * [lsof](#tool-lsof)
  * [netstat](#tool-netstat)
  * [rsync](#tool-rsync)
- **[Programming](#programming)**
  * [awk](#tool-awk)
  * [sed](#tool-sed)
  * [grep](#tool-grep)

<a name="system"><b>System</b></a>

##### Tool: [terminal](https://en.wikipedia.org/wiki/Linux_console)

###### Close shell keeping all subprocess running

```bash
disown -a && exit
```

###### Exit without saving shell history

```bash
kill -9 $$
unset HISTFILE && exit
```

###### Perform a branching conditional

```bash
true && { echo success;} || { echo failed; }
```

###### Pipe stdout and stderr to separate commands

```bash
some_command > >(/bin/cmd_for_stdout) 2> >(/bin/cmd_for_stderr)
```

###### Pipe stdout and stderr to separate commands

```bash
(some_command 2>&1 1>&3 | tee errorlog ) 3>&1 1>&2 | tee stdoutlog
```

###### List of commands you use most often

```bash
history | awk '{ a[$2]++ } END { for(i in a) { print a[i] " " i } }' | sort -rn | head
```

###### Quickly backup a file

```bash
cp filename{,.orig}
```

###### Delete all files in a folder that don't match a certain file extension

```bash
rm !(*.foo|*.bar|*.baz)
```

###### Edit a file on a remote host using vim

```bash
vim scp://user@host//etc/fstab
```

###### Create a directory and change into it at the same time

```bash
mkd () { mkdir -p "$@" && cd "$@"; }
```

###### Convert uppercase files to lowercase files

```bash
rename 'y/A-Z/a-z/' *
```

###### Print a row of characters across the terminal

```bash
printf "%`tput cols`s" | tr ' ' '#'
```

###### Show shell history without line numbers

```bash
history | cut -c 8-
fc -l -n 1 | sed 's/^\s*//'
```

___

##### Tool: [mount](https://en.wikipedia.org/wiki/Mount_(Unix))

###### Mount a temporary ram partition

```bash
mount -t tmpfs tmpfs /mnt -o size=64M
```

  * `-t` - filesystem type
  * `-o` - mount options

___

##### Tool: [fuser](https://en.wikipedia.org/wiki/Fuser_(Unix))

###### Kills a process that is locking a file

```bash
fuser -k filename
```

###### Show what PID is listening on specific port

```bash
fuser -v 53/udp
```

___

##### Tool: [ps](https://en.wikipedia.org/wiki/Ps_(Unix))

###### Show a 4-way scrollable process tree with full details

```bash
ps awwfux | less -S
```

###### Processes per user counter

```bash
ps hax -o user | sort | uniq -c | sort -r
```

___

##### Tool: [find](https://en.wikipedia.org/wiki/Find_(Unix))

###### Find files that have been modified on your system in the past 60 minutes

```bash
find / -mmin 60 -type f
```

###### Find all files larger than 20M

```bash
find / -type f -size +20M
```

###### Find duplicate files (based on MD5 hash)

```bash
find -type f -exec md5sum '{}' ';' | sort | uniq --all-repeated=separate -w 33
```

###### Change permission only for files

```bash
cd /var/www/site && find . -type f -exec chmod 766 {} \;
cd /var/www/site && find . -type f -exec chmod 664 {} +
```

###### Change permission only for directories

```bash
cd /var/www/site && find . -type d -exec chmod g+x {} \;
cd /var/www/site && find . -type d -exec chmod g+rwx {} +
```

###### Find files and directories for specific user

```bash
find . -user <username> -print
```

###### Find files and directories for all without specific user

```bash
find . \!-user <username> -print
```

###### Delete older files than 60 days

```bash
find . -type f -mtime +60 -delete
```

___

##### Tool: [top](https://en.wikipedia.org/wiki/Top_(software))

###### Use top to monitor only all processes with the specific string

```bash
top -p $(pgrep -d , <str>)
```

  * `<str>` - process containing str (eg. nginx, worker)

___

##### Tool: [diff](https://en.wikipedia.org/wiki/Diff)

###### Compare two directory trees

```bash
diff <(cd directory1 && find | sort) <(cd directory2 && find | sort)
```

___

##### Tool: [tail](https://en.wikipedia.org/wiki/Tail_(Unix))

###### Annotate tail -f with timestamps

```bash
tail -f file | while read; do echo "$(date +%T.%N) $REPLY"; done
```

###### Analyse an Apache access log for the most common IP addresses

```bash
tail -10000 access_log | awk '{print $1}' | sort | uniq -c | sort -n | tail
```

___

##### Tool: [tar](https://en.wikipedia.org/wiki/Tar_(computing))

###### System backup with exclude specific directories

```bash
cd /
tar -czvpf /mnt/system$(date +%d%m%Y%s).tgz --directory=/ --exclude=proc/* --exclude=sys/* --exclude=dev/* --exclude=mnt/* .
```

___

##### Tool: [dump](https://en.wikipedia.org/wiki/Dump_(program))

###### System backup to file

```bash
dump -y -u -f /backup/system$(date +%d%m%Y%s).lzo /
```

###### Restore system from lzo file

```bash
cd /
restore -rf /backup/system$(date +%d%m%Y%s).lzo
```

___

##### Tool: [cpulimit](http://cpulimit.sourceforge.net/)

###### Limit the cpu usage of a process

```bash
cpulimit -p pid -l 50
```

##### Tool: [pwdx](https://www.cyberciti.biz/faq/unix-linux-pwdx-command-examples-usage-syntax/)

###### Show current working directory of a process

```bash
pwdx <pid>
```

___

##### Tool: [taskset](https://www.cyberciti.biz/faq/taskset-cpu-affinity-command/)

###### Start a command on only one CPU core

```bash
taskset -c 0 <command>
```

___

##### Tool: [tr](https://en.wikipedia.org/wiki/Tr_(Unix))

###### Show directories in the PATH, one per line

```bash
tr : '\n' <<<$PATH
```

##### Tool: [chmod](https://en.wikipedia.org/wiki/Chmod)

###### Remove executable bit from all files in the current directory

```bash
chmod -R -x+X *
```

___

##### Tool: [who](https://en.wikipedia.org/wiki/Who_(Unix))

###### Find last reboot time

```bash
who -b
```

___

##### Tool: [screen](https://en.wikipedia.org/wiki/GNU_Screen)

###### Start screen in detached mode

```bash
screen -d -m [<command>]
```

___

##### Tool: [du](https://en.wikipedia.org/wiki/GNU_Screen)

###### Show 20 biggest directories with 'K M G'

```bash
du | sort -r -n | awk '{split("K M G",v); s=1; while($1>1024){$1/=1024; s++} print int($1)" "v[s]"\t"$2}' | head -n 20
```

##### Tool: [inotifywait](https://en.wikipedia.org/wiki/GNU_Screen)

###### Init tool everytime a file in a directory is modified

```bash
while true ; do inotifywait -r -e MODIFY dir/ && ls dir/ ; done;
```

##### Tool: [openssl](https://www.openssl.org/)

###### Testing connection to remote host

```bash
echo | openssl s_client -connect google.com:443 -showcerts
```

###### Testing connection to remote host with specific ssl version

```bash
openssl s_client -tls1_2 -connect google.com:443
```

###### Testing connection to remote host with specific ssl cipher

```bash
openssl s_client -cipher 'AES128-SHA' -connect google.com:443
```

###### Generate private key

```bash
# _ciph: des3, aes
( _ciph="des3" ; _fd="private.key" ; _len="2048" ; \
openssl genrsa -${_ciph} -out ${_fd} ${_len} )
```

###### Remove password from private key

```bash
( _fd="private.key" ; _fd_unp="private_unp.key" ; \
openssl rsa -in ${_fd} -out ${_fd_unp} )
```

###### Get public key from private key

```bash
( _fd="private.key" ; _fd_pub="public.key" ; \
openssl rsa -pubout -in ${_fd} -out ${_fd_pub} )
```

###### Generate private key + csr

```bash
( _fd="private.key" ; _fd_csr="request.csr" ; _len="2048" ; \
openssl req -out ${_fd_csr} -new -newkey rsa:${_len} -nodes -keyout ${_fd} )
```

###### Generate csr

```bash
( _fd="private.key" ; _fd_csr="request.csr" ; \
openssl req -out ${_fd_csr} -new -key ${_fd} )
```

###### Generate csr (metadata from exist certificate)

```bash
( _fd="private.key" ; _fd_csr="request.csr" ; _fd_crt="cert.crt" ; \
openssl x509 -x509toreq -in ${_fd_crt} -out ${_fd_csr} -signkey ${_fd} )
```

###### Generate csr with -config param

```bash
( _fd="private.key" ; _fd_csr="request.csr" ; \
openssl req -new -sha256 -key ${_fd} -out ${_fd_csr} \
-config <(
cat <<-EOF
[req]
default_bits = 2048
prompt = no
default_md = sha256
req_extensions = req_ext
distinguished_name = dn

[ dn ]
C=<two-letter ISO abbreviation for your country>
ST=<state or province where your organization is legally located>
L=<city where your organization is legally located>
O=<legal name of your organization>
OU=<section of the organization>
CN=<fully qualified domain name>

[ req_ext ]
subjectAltName = @alt_names

[ alt_names ]
DNS.1 = <fully qualified domain name>
DNS.2 = <next domain>
DNS.3 = <next domain>
EOF
))
```

###### Convert DER to PEM

```bash
( _fd_der="cert.crt" ; _fd_pem="cert.pem" ; \
openssl x509 -in ${_fd_der} -inform der -outform pem -out ${_fd_pem} )
```

###### Convert PEM to DER

```bash
( _fd_der="cert.crt" ; _fd_pem="cert.pem" ; \
openssl x509 -in ${_fd_pem} -outform der -out ${_fd_der} )
```

###### Checking whether the private key and the certificate match

```bash
(openssl rsa -noout -modulus -in private.key | openssl md5 ; openssl x509 -noout -modulus -in certificate.crt | openssl md5) | uniq
```

___

##### Tool: [gnutls-cli](https://gnutls.org/manual/html_node/gnutls_002dcli-Invocation.html)

###### Testing connection to remote host (with sni)

```bash
gnutls-cli -p 443 google.com
```

###### Testing connection to remote host (without sni)

```bash
gnutls-cli --disable-sni -p 443 google.com
```

<a name="http-https"><b>HTTP/HTTPS</b></a>

##### Tool: [curl](https://curl.haxx.se)

```bash
curl -Iks https://www.google.com
```

  * `-I` - show response headers only
  * `-k` - insecure connection when using ssl
  * `-s` - silent mode (not display body)

```bash
curl -Iks --location -X GET -A "x-agent" https://www.google.com
```

  * `--location` - follow redirects
  * `-X` - set method
  * `-A` - set user-agent

```bash
curl -Iks --location -X GET -A "x-agent" --proxy http://127.0.0.1:16379 https://www.google.com
```

  * `--proxy [socks5://|http://]` - set proxy server

___

##### Tool: [httpie](https://httpie.org/)

```bash
http -p Hh https://www.google.com
```

  * `-p` - print request and response headers
    * `H` - request headers
    * `B` - request body
    * `h` - response headers
    * `b` - response body

```bash
http -p Hh --follow --max-redirects 5 --verify no https://www.google.com
```

  * `-F, --follow` - follow redirects
  * `--max-redirects N` - maximum for `--follow`
  * `--verify no` - skip SSL verification

```bash
http -p Hh --follow --max-redirects 5 --verify no --proxy http:http://127.0.0.1:16379 https://www.google.com
```

  * `--proxy [http:]` - set proxy server

<a name="network"><b>Network</b></a>

##### Tool: [ssh](https://www.openssh.com/)

###### Compare a remote file with a local file

```bash
ssh user@host cat /path/to/remotefile | diff /path/to/localfile -
```

###### SSH connection through host in the middle

```bash
ssh -t reachable_host ssh unreachable_host
```

###### Run command over ssh on remote host

```bash
cat > cmd.txt << __EOF__
cat /etc/hosts
__EOF__

ssh host -l user $(<cmd.txt)
```

###### Get public key from private key

```bash
ssh-keygen -y -f ~/.ssh/id_rsa
```

___

##### Tool: [linux-dev](https://www.tldp.org/LDP/abs/html/devref1.html)

###### Testing remote connection to port

```bash
timeout 1 bash -c "</dev/<proto>/<host>/<port>" >/dev/null 2>&1 ; echo $?
```

  * `<proto` - set protocol (tcp/udp)
  * `<host>` - set remote host
  * `<port>` - set destination port

###### Read and write to TCP or UDP sockets with common bash tools

```bash
exec 5<>/dev/tcp/<host>/<port>; cat <&5 & cat >&5; exec 5>&-
```

___

##### Tool: [tcpdump](http://www.tcpdump.org/)

```bash
tcpdump -ne -i eth0 -Q in host 192.168.252.1 and port 443
```

  * `-n` - don't convert addresses
  * `-e` - print the link-level headers
  * `-i [iface]` - set interface
  * `-Q|-D [in|out|inout]` - choose send/receive direction (`-D` - for old tcpdump versions)
  * `host [ip|hostname]` - set host, also `[host not]`
  * `[and|or]` - set logic
  * `port [1-65535]` - set port number, also `[port not]`

```bash
tcpdump -ne -i eth0 -Q in host 192.168.252.1 and port 443 -c 5 -w tcpdump.pcap
```

  * `-c [num]` - capture only num number of packets
  * `-w [filename]` - write packets to file, `-r [filename]` - reading from file

___

##### Tool: [ngrep](http://ngrep.sourceforge.net/usage.html)

```bash
ngrep -d eth0 "www.google.com" port 443
```

  * `-d [iface|any]` - set interface
  * `[domain]` - set hostname
  * `port [1-65535]` - set port number

```bash
ngrep -d eth0 "www.google.com" (host 10.240.20.2) and (port 443)
```

  * `(host [ip|hostname])` - filter by ip or hostname
  * `(port [1-65535])` - filter by port number

```bash
ngrep -d eth0 -qt -O ngrep.pcap "www.google.com" port 443
```

  * `-q` - quiet mode (only payloads)
  * `-t` - added timestamps
  * `-O [filename]` - save output to file, `-I [filename]` - reading from file

```bash
ngrep -d eth0 -qt 'HTTP' 'tcp'
```

  * `HTTP` - show http headers
  * `tcp|udp` - set protocol
  * `[src|dst] host [ip|hostname]` - set direction for specific node

```bash
ngrep -l -q -d eth0 -i "User-Agent: curl*"
```

  * `-l` - stdout line buffered
  * `-i` - case-insensitive search

___

##### Tool: [hping3](http://www.hping.org/)

```bash
hping3 -V -p 80 -s 5050 <scan_type> www.google.com
```

  * `-V|--verbose` - verbose mode
  * `-p|--destport` - set destination port
  * `-s|--baseport` - set source port
  * `<scan_type>` - set scan type
    * `-F|--fin` - set FIN flag, port open if no reply
    * `-S|--syn` - set SYN flag
    * `-P|--push` - set PUSH flag
    * `-A|--ack` - set ACK flag (use when ping is blocked, RST response back if the port is open)
    * `-U|--urg` - set URG flag
    * `-Y|--ymas` - set Y unused flag (0x80 - nullscan), port open if no reply
    * `-M 0 -UPF` - set TCP sequence number and scan type (URG+PUSH+FIN), port open if no reply

```bash
hping3 -V -c 1 -1 -C 8 www.google.com
```

  * `-c [num]` - packet count
  * `-1` - set ICMP mode
  * `-C|--icmptype [icmp-num]` - set icmp type (default icmp-echo = 8)

```bash
hping3 -V -c 1000000 -d 120 -S -w 64 -p 80 --flood --rand-source <remote_host>
```

  * `--flood` - sent packets as fast as possible (don't show replies)
  * `--rand-source` - random source address mode
  * `-d --data` - data size
  * `-w|--win` - winsize (default 64)

___

##### Tool: [netcat](http://netcat.sourceforge.net/)

```bash
nc -kl 5000
```

  * `-l` - listen for an incoming connection
  * `-k` - listening after client has disconnected
  * `>filename.out` - save receive data to file (optional)

```bash
nc 192.168.0.1 5051 < filename.in
```

  * `< filename.in` - send data to remote host

```bash
nc -vz 10.240.30.3 5000
```

  * `-v` - verbose output
  * `-z` - scan for listening daemons

```bash
nc -vzu 10.240.30.3 1-65535
```

  * `-u` - scan only udp ports

###### Transfer data file (archive)

```bash
server> nc -l 5000 | tar xzvfp -
client> tar czvfp - /path/to/dir | nc 10.240.30.3 5000
```

###### Launch remote shell

```bash
server> nc -l 5000 -e /bin/bash
client> nc 10.240.30.3 5000
```

###### Simple file server

```bash
while true ; do nc -l 5000 | tar -xvf - ; done
```

###### Simple HTTP Server

  > Restarts web server after each request - remove `while` condition for only single connection.

```bash
cat > index.html << __EOF__
<!doctype html>
    <head>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
        <title></title>
        <meta name="description" content="">
        <meta name="viewport" content="width=device-width, initial-scale=1">
    </head>
    <body>

    <p>

      Hello! It's a site.

    </p>

    </body>
</html>
__EOF__
```

```bash
server> while : ; do \
(echo -ne "HTTP/1.1 200 OK\r\nContent-Length: $(wc -c <index.html)\r\n\r\n" ; cat index.html;) \
| nc -l -p 5000 \
; done
```

  * `-p` - port number

###### Simple HTTP Proxy (single connection)

```bash
#!/usr/bin/env bash

if [[ $# != 2 ]] ; then
  printf "%s\\n" \
         "usage: ./nc-proxy listen-port bk_host:bk_port"
fi

_listen_port="$1"
_bk_host=$(echo "$2" | cut -d ":" -f1)
_bk_port=$(echo "$2" | cut -d ":" -f2)

printf "  lport: %s\\nbk_host: %s\\nbk_port: %s\\n\\n" \
       "$_listen_port" "$_bk_host" "$_bk_port"

_tmp=$(mktemp -d)
_back="$_tmp/pipe.back"
_sent="$_tmp/pipe.sent"
_recv="$_tmp/pipe.recv"

trap 'rm -rf "$_tmp"' EXIT

mkfifo -m 0600 "$_back" "$_sent" "$_recv"

sed "s/^/=> /" <"$_sent" &
sed "s/^/<=  /" <"$_recv" &
nc -l -p "$_listen_port" <"$_back" \
  | tee "$_sent" \
  | nc "$_bk_host" "$_bk_port" \
  | tee "$_recv" >"$_back"
```

```bash
server> chmod +x nc-proxy && ./nc-proxy 8080 192.168.252.10:8000
  lport: 8080
bk_host: 192.168.252.10
bk_port: 8000

client> http -p h 10.240.30.3:8080
HTTP/1.1 200 OK
Accept-Ranges: bytes
Cache-Control: max-age=31536000
Content-Length: 2748
Content-Type: text/html; charset=utf-8
Date: Sun, 01 Jul 2018 20:12:08 GMT
Last-Modified: Sun, 01 Apr 2018 21:53:37 GMT
```

###### Create a single-use TCP or UDP proxy

```bash
### TCP -> TCP
nc -l -p 2000 -c "nc [ip|hostname] 3000"

### TCP -> UDP
nc -l -p 2000 -c "nc -u [ip|hostname] 3000"

### UDP -> UDP
nc -l -u -p 2000 -c "nc -u [ip|hostname] 3000"

### UDP -> TCP
nc -l -u -p 2000 -c "nc [ip|hostname] 3000"
```

___

##### Tool: [socat](http://www.dest-unreach.org/socat/doc/socat.html/)

###### Testing remote connection to port

```bash
socat - TCP4:10.240.30.3:22
```

  * `-` - standard input (STDIO)
  * `TCP4:<params>` - set tcp4 connection with specific params
    * `[hostname|ip]` - set hostname/ip
    * `[1-65535]` - set port number

###### Redirecting TCP-traffic to a UNIX domain socket under Linux

```bash
socat TCP-LISTEN:1234,bind=127.0.0.1,reuseaddr,fork,su=nobody,range=127.0.0.0/8 UNIX-CLIENT:/tmp/foo
```

  * `TCP-LISTEN:<params>` - set tcp listen with specific params
    * `[1-65535]` - set port number
    * `bind=[hostname|ip]` - set bind hostname/ip
    * `reuseaddr` - allows other sockets to bind to an address
    * `fork` - keeps the parent process attempting to produce more connections
    * `su=nobody` - set user
    * `range=[ip-range]` - ip range
  * `UNIX-CLIENT:<params>` - communicates with the specified peer socket
    * `filename` - define socket

___

##### Tool: [lsof](https://en.wikipedia.org/wiki/Lsof)

###### Show process that use internet connection at the moment

```bash
lsof -P -i -n
```

###### Show process that use specific port number

```bash
lsof -i tcp:443
```

###### Lists all listening ports together with the PID of the associated process

```bash
lsof -Pan -i tcp -i udp
```

###### List all open ports and their owning executables

```bash
lsof -i -P | grep -i "listen"
```

###### Show open ports

```bash
lsof -Pni4 | grep LISTEN | column -t
```

###### List all files opened by a particular command

```bash
lsof -c "process"
```

###### View user activity per directory

```bash
lsof -u username -a +D /etc
```
___

##### Tool: [netstat](https://en.wikipedia.org/wiki/Netstat)

###### Graph # of connections for each hosts

```bash
netstat -an | grep ESTABLISHED | awk '{print $5}' | awk -F: '{print $1}' | grep -v -e '^[[:space:]]*$' | sort | uniq -c | awk '{ printf("%s\t%s\t",$2,$1) ; for (i = 0; i < $1; i++) {printf("*")}; print "" }'
```

###### Monitor open connections for specific port including listen, count and sort it per IP

```bash
watch "netstat -plan | grep :443 | awk {'print \$5'} | cut -d: -f 1 | sort | uniq -c | sort -nk 1"
```

___

##### Tool: [rsync](https://en.wikipedia.org/wiki/Rsync)

###### Rsync remote data as root using sudo

```bash
rsync --rsync-path 'sudo rsync' username@hostname:/path/to/dir/ /local/
```

<a name="programming"><b>Programming</b></a>

##### Tool: [awk](http://www.grymoire.com/Unix/Awk.html)

###### Remove duplicate entries in a file without sorting

```bash
awk '!x[$0]++' filename
```

###### Exclude multiple columns using AWK

```bash
awk '{$1=$3=""}1' filename
```

___

##### Tool: [sed](http://www.grymoire.com/Unix/Sed.html)

###### To print a specific line from a file

```bash
sed -n 10p /path/to/file
```

###### Remove a specific line from a file

```bash
sed -i 10d /path/to/file
```

###### Remove a range of lines from a file

```bash
sed -i <file> -re '<start>,<end>d'
```

___

##### Tool: [grep](http://www.grymoire.com/Unix/Grep.html)

###### Search for a "pattern" inside all files in the current directory

```bash
grep -RnisI "pattern" *
fgrep "pattern" * -R
```

###### Remove blank lines from a file and save output to new file

```bash
grep . filename > newfilename
```

###### Except multiple patterns

```bash
grep -vE '(error|critical|warning)' filename
```

###### Show data from file without comments

```bash
grep -v ^[[:space:]]*# filename
```

###### Show data from file without comments and new lines

```bash
egrep -v '#|^$' filename
```