Fincer
/
linux-server-setup
mirror of https://github.com/Fincer/linux-server-setup

Linux servers - Exercice 4==============
*Disclaimer:*--------------
This exercise is a part of [Linux servers (ICT4TN021, spring 2018) // Linux-palvelimet (ICT4TN021, kevät 2018)](http://www.haaga-helia.fi/fi/opinto-opas/opintojaksokuvaukset/ICT4TN021) school course organized as a part of Information Technology studies in Haaga-Helia university of Applied Sciences, Helsinki, Finland. Course lecturer [Tero Karvinen](http://terokarvinen.com/) has defined the original assignment descriptions in Finnish presented in this document in English. Answers and translations have been written by Pekka Helenius (me, ~ Fincer).
**a)** Make it possible to create home pages with normal user privileges in your virtual server environment.--------------
**Answer:**
Virtual server IP address is _174.138.2.190_. The server is hosted on [DigitalOcean](https://www.digitalocean.com/community/tutorials/how-to-create-your-first-digitalocean-droplet) which provides hosting services for users. Ubuntu 16.04 LTS (without DE) is used as a server platform.
Ubuntu distribution hosted on DigitalOcean has custom configurations compared to Canonical version of clean Ubuntu environment. For example, DigitalOcean has predefined different repository sources in package manager sources file _/etc/apt/sources.list_ (http://mirrors.digitalocean.com/ubuntu/) and has customized configuration for Apache web server by default. Can you trust these repositories and predefined configurations as a system administrator? Can you be sure the program source codes are "clean" and do not contain malicious code patches? Are the used package repositories updated and which flags have been used to compile the binary software available there? What differences are there between the official Canonical and DigitalOcean repositories?
It is good to stop to think the previous issues before looking for a third party hosting service for your server environment. Do available markets have better virtual hosting service providers and in which criteria? In small business, it can be safer to hold all the aces and set up a minimal self-hosted server using a computer (suited for your needs) such as Raspberry Pi and claim a Domain name for it from a DNS provider. If you do larger business, you need to consider your server capacity again. It can be more profitable and comfortable to buy some server space from a virtual hosting server provider.
Of course, if you ever want to, you can install the server environment from scratch using rolling releases such as Arch Linux, Gentoo or 'Linux from Scratch'. However, this is not recommended approach in server environments requiring system stability over newer software.
Anyway,
1. Do initial configuration for your server following the guide by Tero Karvinen:
[Tero Karvinen - First Steps on a New Virtual Private Server – an Example on DigitalOcean and Ubuntu 16.04 LTS](http://terokarvinen.com/2017/first-steps-on-a-new-virtual-private-server-an-example-on-digitalocean)
2. Connect to your new virtual private server once you have set it up. I use a predefined user name _newuser_ in my server environment:
```phelenius@my-machine:~$ ssh newuser@174.138.2.190newuser@174.138.2.190's password: Welcome to Ubuntu 16.04.3 LTS (GNU/Linux x86_64)
 * Documentation:  https://help.ubuntu.com * Management:     https://landscape.canonical.com * Support:        https://ubuntu.com/advantage
  Get cloud support with Ubuntu Advantage Cloud Guest:    http://www.ubuntu.com/business/services/cloud
7 packages can be updated.0 updates are security updates.

Last login: Tue Feb 13 14:49:24 2018 from XXX.XXX.XXX.XXXnewuser@goauldhost:~$ ```
3. Open default SSH TCP port 22 in your firewall:
**NOTE!** Default policy for Ubuntu firewall is to deny/drop all input connections so we need to allow traffic into protocol/daemon specific ports to open up communication between this server and clients.
```newuser@goauldhost:~$ sudo ufw allow 22/tcp && sudo ufw enable```
Once you have established SSH connection to your remote server, install _apache2_ and open port 80 for it doing the following:
```newuser@goauldhost:~$ sudo apt-get install apache2 && sudo ufw allow 80/tcp```
4. Enable Apache _userdir_ module:
```newuser@goauldhost:~$ sudo a2enmod userdir```
5. Some PHP and userdir module related configurations seem to be predefined in packages provided on DigitalOcean server environment (such as # symbols in /etc/apache2/mods-enabled/php7.0.conf in order to enable PHP for user sites), unlike stated in [Exercise 3](https://github.com/Fincer-altego/basics-of-a-linux-server-school-course-/blob/master/h3.md).
6. Restart Apache HTTP daemon (HTTPD) after enabling _userdir_ module:
```newuser@goauldhost:~$ sudo systemctl restart apache2.service```
Recheck HTTP daemon state (should be **Running**):
```newuser@goauldhost:~$ systemctl status apache2.service```
If everything seem to be running and working you can try to establish connection to the HTTP daemon server using _your local computer_ (do not try this in your virtual private server environment but with an external client computer):
```phelenius@my-machine:~$ xdg-open http://174.138.2.190:80```
The IP address here refers to the virtual private server IP address.
7. If the connection test is successful, you should see something similar to this picture:
![apache2-defaultpage](https://www.dedyprastyo.com/wp-content/uploads/2017/10/Install-Apache-di-Ubuntu-17.04-www.dedyprastyo.com_-400x400.jpg)
Let's get back to the virtual server environment in our SSH session.
8. We should hide any extra server information which is visible for clients. Add the following lines in _/etc/apache2/apache2.conf_ (with sudoedit):
```TraceEnable OffServerSignature OffServerTokens Prod```
Description of these lines [here](https://www.petefreitag.com/item/419.cfm).
Restart Apache HTTP daemon (web server):```newuser@goauldhost:~$ sudo systemctl restart apache2.service```
9. Create a new user _monkey_ (finnish: apina). We do not add this user to _sudo_ groups, therefore denying all root access for this user:
```newuser@goauldhost:~$ sudo adduser monkey```
Change to the default shell of user _monkey_ (you can check it by executing: _grep monkey /etc/passwd_):
```newuser@goauldhost:~$ su monkeyPassword: monkey@goauldhost:/home/newuser$ cdmonkey@goauldhost:~$ mkdir public_html```
Therefore we have created a new home site folder for the user _monkey_. Contents of this folder should be available like shown in the following picture:
![monkeysite-samplepic](https://raw.githubusercontent.com/Fincer-altego/basics-of-a-linux-server-school-course-/master/monkey-site.png)
**NOTE!** As you can see, Apache doesn't give any server information in the website view, thanks for the configurations done in step 8.
User _monkey_ can add any content to his/her personal site. By default, Apache looks for any of the following files, defined in _/etc/apache2/mods-available/dir.conf_ (symbolic link in folder _/etc/apache2/mods-enabled/dir.conf_):
```newuser@goauldhost:~$ ls -l /etc/apache2/mods-enabled/dir.conflrwxrwxrwx 1 root root 26 Feb  8 10:40 /etc/apache2/mods-enabled/dir.conf -> ../mods-available/dir.confnewuser@goauldhost:~$ cat /etc/apache2/mods-enabled/dir.conf |grep -i directoryindex | awk '{$1 = ""; print $i}' index.html index.cgi index.pl index.php index.xhtml index.htm```
Permissions of folder $HOME/public_html of the user _monkey_ are as follows:
```monkey@goauldhost:~$ ls -ltotal 4drwxrwxr-x 2 monkey monkey 4096 Feb 13 15:35 public_html```drwxrwxr-x123456789 10
d = directoryr = read (value 4)w = write (value 2)x = execute (value 1)
where ...symbols 2-4 (rwx) indicate permissions of the user _monkey_ to the folder...symbols 5-7 (rwx) indicate permissions of the (primary) group where the user _monkey_ belongs to. In this case, the group is _monkey_...symbols 8-10 (r-x) indicate permissions granted for other system users to the folder
Permissions can be written in numeric form but also in symbolic form. For example,
775 = rwxrwxr-x (4+2+1, 4+2+1, 4+1)ug=rwx,o=rx = rwxrwxr-x
Take a look on the following links to get more information about Unix permissions:
- [Arch Wiki - File permissions and attributes](https://wiki.archlinux.org/index.php/File_permissions_and_attributes)
- [Wikipedia - Notation_of_traditional_Unix_permissions](https://en.wikipedia.org/wiki/File_system_permissions#Notation_of_traditional_Unix_permissions)
- [Arch Wiki - umask](https://wiki.archlinux.org/index.php/Umask)
Changing permissions is recommended to be done in symbolic mode because individual permissions can't be as flexibly be changed in numeric mode.
ls command shows a user (monkey) first after which group (monkey) is shown.
The folder is accessible in public network via address _http://174.138.2.190:80/~monkey/_
You can change permissions with _chmod_ command. 
Numeric form:chmod 775 ~/public_html
Symbolic form:chmod ug=rwx,o=rx ~/public_html
You can change permissions recursively using _-R_ parameter (chmod -R ...)
**EXTRA: Deleting Server field from HTTP header by updating Apache source code on Debian-based Linux distributions**--------------
Including Server field in HTTP header by Apache HTTP daemon  (web server) is debated. [HTTP/1.1 standard specification](https://tools.ietf.org/html/rfc2616#page-141) states the following:
> Note: Revealing the specific software version of the server might allow the server machine to become more vulnerable to attacks against software that is known to contain security holes. Server implementors are encouraged to make this field a configurable option.

**NOTE!** Apache is compiled from source code.
Removal of Server field from HTTP header is debated in Apache developers' community (The key question here: does removal of the field actually improve any security?). More about this topic: [StackoverFlow (Can't remove Server: Apache header)](https://stackoverflow.com/questions/35360516/cant-remove-server-apache-header).
**NOTE!** The following method does not work with automatic system updates via package repositories (usage of _sudo apt-get update_ and _sudo apt-get upgrade_ commands) because the patches binary files would be replaced by ones available in the official repositories. Therefore, each time you want to update your Apache server, you need to recompile it from source applying the patch file provided in this GitHub repository. _This method can be troublesome for system administration or contain unaccepted policy in your company. Consider using puppet or salt or any relevant automation method here._
**NOTE!** You must be aware what you are doing each time you compile software from source. Trust the source, trust the patch files (diff or patch) and do not do anything that can lead to unknown or troublesome bugs, malicious code execution or create new security risks.
**NOTE!** We are unable to sign the package with the official maintainer key because we update Apache with our specific patch file and compile the software ourselves. Therefore we ignore any signing requirements in _dpkg-buildpackage_ command (or alternatively we can use our own keys).
**NOTE** Consider any policy that determines your production and/or server environment requirements. For example: Am I allowed to install software from source code? Does my method break a (critical) component in working server environment? Etc.
**NOTE!** _Again. Know exactly what you are about to do. As a system administrator you hold responsibility here._
We have already improved security of our Apache web server by removing critical information sent to client. However, the server still gives information about its name as follows:
```newuser@goauldhost:~/source_codes/apache2$ curl -I http://localhostHTTP/1.1 200 OKDate: Sat, 17 Feb 2018 13:27:11 GMTServer: ApacheContent-Type: text/html;charset=UTF-8```
We want to remove field _Server: Apache_. Multiple approaches were tested (such as modsecurity2 module and writing line _Header unset Server_ into file _/etc/apache2/apache2.conf_) without success. Therefore I ended up patching the source code of Apache web server so that the wanted field can really be removed.
Download Apache source code on your Debian-based Linux distribution:
```newuser@goauldhost:~$ mkdir -p ./source_codes/apache2 && cd ./source_codes/apache2newuser@goauldhost:~/source_codes/apache2$ apt-get source apache2```
After which add [source code patch file](https://github.com/Fincer-altego/basics-of-a-linux-server-school-course-/blob/e60bfe23814f5b72315daec144c31a75bc7f1ef0/patch_apache_servertokens.patch) into created _$HOME/source_codes/apache2_ folder.
**NOTE!** I have personally created the patch file with Unix tool _diff_. The patch file is not downloaded from any suspicious website. You can always check the patch file code yourself if still hesitating.
If you have a working Apache HTTP daemon (web server) environment on your Linux, please check the version of your Apache software version with the following command:
```newuser@goauldhost:~$ dpkg -s apache2 |grep -i versionVersion: 2.4.18-2ubuntu3.5```
In that way we can be sure version of the downloaded source code matches with our already-installed Apache environment.
Once you have downloaded the source code, go to the following folder (which contains the code):
```newuser@goauldhost:~/source_codes/apache2$ cd apache2-2.4.18/```
Implement the patch file changes into the Apache source code:
```newuser@goauldhost:~/source_codes/apache2/apache2-2.4.18$ patch -Np1 -i ../patch_apache_servertokens.patch```
Before compiling Apache web server, you must install the following build time dependencies:
```newuser@goauldhost:~/source_codes/apache2/apache2-2.4.18$ sudo apt-get install debhelper libaprutil1-dev libapr1-dev libpcre3-dev zlib1g-dev libssl-dev liblua5.1-0-dev libxml2-dev autotools-dev build-essential```
Compile and install the Apache web server:
newuser@goauldhost:~/source_codes/apache2/apache2-2.4.18$ dpkg-buildpackage -rfakeroot -b -us -uc...<compiling source code>...<source code compiled and archived as new deb packages>```
If Apache HTTP daemon is running, stop it:
```newuser@goauldhost:~/source_codes/apache2$ sudo systemctl stop apache2.service```
It is essential to check which apache2 packages have been installed into the target system. We want to install only specific deb packages already found in the system, as multiple deb packages have been compiled by the previous command. All found Apache2 packages in the system should be replaced by the ones compiled from the Apache2 source code. 
System has the following Apache2 packages:
```newuser@goauldhost:~/source_codes/apache2/apache2-2.4.18$ cd ..newuser@goauldhost:~/source_codes/apache2$ dpkg --get-selections |grep apache | awk '{print $1}'apache2apache2-binapache2-dataapache2-utilslibapache2-mod-phplibapache2-mod-php7.0```
Then we compare the above list to the compiled deb packages:
```newuser@goauldhost:~/source_codes/apache2$ ls |grep debapache2_2.4.18-2ubuntu3.5_amd64.debapache2_2.4.18-2ubuntu3.5.debian.tar.xzapache2-bin_2.4.18-2ubuntu3.5_amd64.debapache2-data_2.4.18-2ubuntu3.5_all.debapache2-dbg_2.4.18-2ubuntu3.5_amd64.debapache2-dev_2.4.18-2ubuntu3.5_amd64.debapache2-doc_2.4.18-2ubuntu3.5_all.debapache2-suexec-custom_2.4.18-2ubuntu3.5_amd64.debapache2-suexec-pristine_2.4.18-2ubuntu3.5_amd64.debapache2-utils_2.4.18-2ubuntu3.5_amd64.deb```
... as a result we can see that the following deb packages should be installed with _dpkg -i_ command:
```newuser@goauldhost:~/source_codes/apache2$ sudo dpkg -i apache2_2.4.18-2ubuntu3.5_amd64.deb apache2-bin_2.4.18-2ubuntu3.5_amd64.deb apache2-data_2.4.18-2ubuntu3.5_all.deb apache2-utils_2.4.18-2ubuntu3.5_amd64.deb```
If everything has succeeded you should have a working, patched Apache web server in your target system. Because the patches web server software supports _ServerTokens None_ option now, we shall add this option into _etc/apache2/apache2.conf_.
```newuser@goauldhost:~$ sudoedit /etc/apache2/apache2.conf```
Add the following lines (// just replace ServerTokens Prod with None):
```TraceEnable OffServerSignature OffServerTokens None```
**NOTE!** Any settings in _/etc/apache2/conf-available/security.conf_ overrides these configuration changes.
Restart Apache2 server (you must apply the patch file before doing this because the default Apache software does not implement 'None' for ServerTokens):
```newuser@goauldhost:~$ sudo systemctl start apache2.service```
Check whether the configuration works:
```phelenius@my-machine:~$ curl -I http://174.138.2.190HTTP/1.1 200 OKDate: Sat, 17 Feb 2018 14:02:20 GMTLast-Modified: Wed, 14 Feb 2018 00:06:44 GMTETag: "20b-56520e2f88f4a"Accept-Ranges: bytesContent-Length: 523Vary: Accept-EncodingContent-Type: text/html```
Therefore we have successfully deleted Server field from HTTP header.
You can additionally set and unset HTTP header fields sent to a client as follows:
```Header unset Last-ModifiedHeader unset Accept-RangesHeader unset VaryHeader unset ETag```
You must be careful when unsetting fields because it affects behavior of client programs and efficiency of your server environment (performance, for example). Remember that factors such as field order, formatting and error messages can give hints about the used server environment as well (for example, 404 not found message). 
**NOTE!** The header options mentioned above work only if module 'headers' has been activated (run command _sudo a2enmod headers_ and restart the server)
More about HTTP header in [Wikipedia](https://en.wikipedia.org/wiki/List_of_HTTP_header_fields). More articles in [ETag](https://en.wikipedia.org/wiki/HTTP_ETag), [Vary: Accept-Encoding](https://blog.stackpath.com/accept-encoding-vary-important), etc.
**s)** Set user default website to be the default website for Apache in your virtual server environment.--------------
**Answer:**
Let's begin from the final state of the previous answer. We have created a user _monkey_ in our server computer. This user has a website URL 174.138.2.190:80/~monkey
1. Remove default webpage of Apache web server, and move _DocumentRoot_ to point to directory *$HOME/public_html* of user *monkey*, after which restart Apache service daemon.
```newuser@goauldhost:~$ sudo sed -i 's?DocumentRoot /var/www/html?DocumentRoot /home/monkey/public_html?' /etc/apache2/sites-available/000-default.conf```
We can disable folder path _/var/www_ commenting out the following lines (inserting # symbols) in file */etc/apache2/apache2.conf* (use command _sudoedit_, for example):
```#<Directory /var/www/>
#        Options Indexes FollowSymLinks
#        AllowOverride None
#        Require all granted
#</Directory>
```
Restart Apache web server daemon:
```newuser@goauldhost:~$ sudo systemctl restart apache2.service```
Go to the following IP address with your _local computer_ (use HTTP port 80):
```xdg-open http://174.138.2.190:80```
The opening view should be as follows:
![emptypage-sample](https://raw.githubusercontent.com/Fincer-altego/basics-of-a-linux-server-school-course-/master/empty-page-sample.png)
2. Create a new file _index.html_ in the directory $HOME/public_html of user _monkey_ (where $HOME=/home/monkey/)
```newuser@goauldhost:~$ su monkeyPassword: monkey@goauldhost:/home/newuser$ cdmonkey@goauldhost:~$ echo -e '<!DOCTYPE html>\n <html>\n \t<head>\n \t\t<title>Testi</title>\n \t</head>\n \t<body>\n \t\t<h1>Testi</h1>\n \t</body>\n </html>\n' > ~/public_html/index.html
```
3. We should redirect all index.html traffic to the folder root _/home/monkey/public_html/. This can be done by creating hidden page-related control file _.htaccess_ file to the directory root.
```monkey@goauldhost:~$ cd public_htmlmonkey@goauldhost:~/public_html$ touch .htaccessmonkey@goauldhost:~/public_html$ echo -e '<IfModule mod_rewrite.c>\n\tRewriteEngine On\n\tRewriteBase /\n\tRewriteRule ^index\.html$ / [NC,R,L]\n</IfModule>' | tee -a ./.htaccess```
Reactivate Apache module 'rewrite'. We shall switch our user because user _monkey_ doesn't have _sudo_ rights at this point:
```monkey@goauldhost:~/public_html$ su newuserPassword: newuser@goauldhost:/home/monkey/public_html$ sudo a2enmod rewriteEnabling module rewrite.To activate the new configuration, you need to run:  service apache2 restartnewuser@goauldhost:/home/monkey/public_html$ sudo systemctl restart apache2.service```
Your Apache web server should redirect all traffic of _http://174.138.2.190:80/index.html_ to address _http://174.138.2.190:80/_
**y)** Find clues of possible penetration attempts to your web server. You can find more information about suspicious IP address without connecting them by using commands ipcalc, geoiplookup and whois, for instance.--------------
**Answer:**
At the time of writing this answer, the Apache web server was running bit over a week period. However, there were no any webpage deployed during that time, and therefore my web server hadn't created any major log entries. However, I noticed one suspicious connection attempt to setup.php file of phpMyAdmin software, although the software was not installed. The lookup was done by checking web server log file _var/log/apache2/access.log_. The log entry itself was as follows:
```66.118.142.165 - - [13/Feb/2018:14:43:58 +0000] "HEAD /phpmyadmin/scripts/setup.php HTTP/1.0" 404 159 "-" "-"```
We shall analyze the logged IP address (+ download a georeferred IP database to determine more specific geolocation of the source by using _wget_ command):
```newuser@goauldhost:~$ sudo apt-get -y install geoip-binnewuser@goauldhost:~$ wget http://geolite.maxmind.com/download/geoip/database/GeoLiteCity.dat.gznewuser@goauldhost:~$ gunzip GeoLiteCity.dat.gznewuser@goauldhost:~$ OBSIP=66.118.142.165newuser@goauldhost:~$ echo -e "Server Geolocation:\n$(geoiplookup -f /home/newuser/GeoLiteCity.dat $OBSIP)\n\n$(nslookup $OBSIP)\n\nDNS Name:\n$(dig +short -x $OBSIP)" && unset OBSIP```
Output is as follows:
```Server Geolocation:GeoIP City Edition, Rev 1: US, FL, Florida, Tampa, 33611, 27.886700, -82.511703, 539, 813
Server:		67.207.67.2Address:	67.207.67.2#53
Non-authoritative answer:165.142.118.66.in-addr.arpa	name = 66-118-142-165.static.sagonet.net.
Authoritative answers can be found from:
DNS Name:66-118-142-165.static.sagonet.net.
```
The log entry tells us that connection to page _http://174.138.2.190:80/phpmyadmin/scripts/setup.php_ was tried to establish. The server responded with code 404 (HTTP_NOT_FOUND), indicating that the address couldn't be found. It is seen that user agent string of _66.118.142.165_ is empty (just a line). It is known that the user agent string can be very easily customized.
HTTP [HEAD method](http://condor.depaul.edu/dmumaugh/readings/handouts/SE435/HTTP/node14.html) were used in the connection attempt. The HTTP HEAD method is more suitable for quick file existence look-ups than HTTP GET method because only the file existence is checked, leading to decreased data transfer rates between a server and a client. The HEAD method is usually used for caching documents (data). A client program just tries to download metadata of the request document from a server. [Apache web server does not return the message response body while answering to the client program with the HTTP HEAD method.](https://hc.apache.org/httpclient-3.x/methods/head.html).
the HEAD method can be "disabled" by adding the following lines into 1) file *~/public_html/.htaccess* (in the case of this assignment) 2) or into file */etc/apache2/sites-available/000-default.conf* 3) or any site-specific configuration file in Apache's _sites-available_ folder 4) or any _.htaccess_ file in a website directory root:
```RewriteEngine onRewriteCond %{THE_REQUEST} !^(POST|GET)\ /.*\ HTTP/1\.1$ RewriteRule .* - [F,L]```
The original answer [here](https://www.linuxquestions.org/questions/linux-security-4/disabling-head-options-http-methods-in-apache-webserver-763347/#post4511023)
It is understandable that line _RewriteEngine on_ doesn't need to be determined twice and adding this code requires re-enabling of Apache rewrite module.
I have had a Debian-based web server (LAMP) environment in the past years. I have included Apache access.log parts of that web server environment here (year 2014):
[Apache - access.log, example](https://raw.githubusercontent.com/Fincer-altego/basics-of-a-linux-server-school-course-/master/apache-log-sample)
The log file reveals many suspicious connection attempts from Thailand and Netherlands, for example.
The most memorable log entry from the past years was, however, a penetration attempt by Romanian hacker/bot group and it looked like the following:
```4.125.148.79 - - [07/Aug/2013:20:53:35 +0400] "GET /w00tw00t.at.blackhats.romanian.anti-sec:) HTTP/1.1" 404 142 "-" "ZmEu"```
**y)** Create a set of websites on your local computer and copy the sites to your web server with scp command.--------------
**Answer:**
1. Let's create the required websites locally, after which the upload is done with user _newuser_. I have used pre-created websites in this assignment. The upload is done with my Arch Linux computer using required SSH protocol:
```[13/02/2018 21:04:16 - fincer: ~ ]$ scp /home/fincer/Documents/website/website_1.03_fincer.zip newuser@174.138.2.190:./The authenticity of host '174.138.2.190 (174.138.2.190)' can't be established.ECDSA key fingerprint is SHA256:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.Are you sure you want to continue connecting (yes/no)? yesWarning: Permanently added '174.138.2.190' (ECDSA) to the list of known hosts.newuser@174.138.2.190's password: website_1.03_fincer.zip                                                                    100%  656KB 655.8KB/s   00:01    [13/02/2018 21:04:32 - fincer: ~ ]$ ```
2. Modify Apache default webpage address to point to _/home/newuser/public_html/_:
```newuser@goauldhost:~$ sudo sed -i 's?DocumentRoot /home/monkey/public_html?DocumentRoot /home/newuser/public_html?' /etc/apache2/sites-available/000-default.confnewuser@goauldhost:~$ sudo systemctl restart apache2.service```
3. Because /home/newuser/public_html/ is empty (checked with ls command), we shall extract uploaded _website_1.03_fincer.zip_ to that directory.
```newuser@goauldhost:~$ sudo apt-get update && sudo apt-get install unzipnewuser@goauldhost:~$ mv website_1.03_fincer.zip ./public_html/ && cd ./public_htmlnewuser@goauldhost:~$ unzip website_1.03_fincer.zip```
4. It should be possible to open the website using URL _174.138.2.190_, and the website should look like the following:
![website-sample](https://raw.githubusercontent.com/Fincer-altego/basics-of-a-linux-server-school-course-/master/pekkahh-website.png)
5. Let's copy another website sample into folder $HOME/public_html/ of user _monkey_:
```[13/02/2018 22:01:40 - fincer: ~ ]$ scp /home/fincer/Documents/server_site.tar.xz monkey@174.138.2.190:./public_html/```
6. Let's establish a new SSH connection to the virtual server computer with user _monkey_:
```[13/02/2018 22:04:23 - fincer: ~ ]$ ssh monkey@174.138.2.190```
7. In the virtual web server computer terminal, go to _$HOME/public_html/ of user _monkey_, extract _server_site.tar.xz_ and put the extracted files into correct places in the directory hierarchy. Rename old _index.html_ file to _index.html.old_
```monkey@goauldhost:~/public_html$ mv index.html index.html.oldmonkey@goauldhost:~/public_html$ tar xf server_site.tar.xzmonkey@goauldhost:~/public_html$ mv ./server_site/* ./monkey@goauldhost:~/public_html$ rm -Rf ./{server_site,server_site.tar.xz}```
(you could have just used one * symbol in the previous rm command because the equal name syntax)
The deployed website can be viewed in URL address _http://174.138.2.190:80/~monkey_, and they look as follows:
![workprice-samplesite](https://raw.githubusercontent.com/Fincer-altego/basics-of-a-linux-server-school-course-/master/workprice-site_example.png)
**y)** Set up a simple PHP webpage on your web server. For instance, you can print a remote address of the user ( $_SERVER['REMOTE_ADDR'] ) etc. Be careful if you use input forms of any kind.--------------
**Answer:**
In this answer, I add a PHP-based BMI calculator (Body Mass Index) to my website. For this purpose, two files were created: _bmicalc.html_ and _bmicalc.php_ which both are uploaded to the virtual web server with the following command, executed at the _local computer_:
```phelenius@my-machine:~$ scp $HOME/public_html/bmi-index/{bmicalc.php,bmicalc.html} newuser@174.138.2.190:./public_html/newuser@174.138.2.190's password:bmicalc.php                                                           100% 3051     3.0KB/s   00:00    bmicalc.html                                                          100%  523     0.5KB/s   00:00 ```
The following image demonstrates a web browser view of URL address _174.138.2.190/bmicalc.html_. On the left side: the source code of the HTML page. On the right side: server-side "raw" PHP source code which is not seen by the client program, our web browser in this case (PHP code = server-side execution/only web server sees the code, JavaScript code = client-side execution/client can see the code, too):
![bmicalc-sample](https://raw.githubusercontent.com/Fincer-altego/basics-of-a-linux-server-school-course-/master/bmicalc-sample.png)
**Edit** The following changes has been done after answering the assignment:
- PHP-related HTTP method GET has been changed to POST method afterwards because usage of the GET method leads to visible input values in a web browser URL field. This doesn't happen when using the POST method.
- Implementation of server-side solutions which restrict user accessibility to other web server directories and files.
- PHP code has been merged with the HTML document, i.e. there is no additional .php file in the web server anymore.