The basics of Linux system administration

Summary

The purpose of this README is to simply administer a Linux system.
In this tutorial we will create users and add them to two new groups.
Then we will give administrator rights to a group.
Then we will see how to generate an RSA key to connect to a machine without a password.
Finally we will finish with the installation of WordPress

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Initialisation

One of the first commands to run on a new Linux system is this one:

sudo apt update -y && sudo apt upgrade -y

It allows to update the system package

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Step 1

This command allows you to create a user with his home folder (his user folder). Once executed you will have to enter the user's password and confirm it. Then you can enter the user's information, otherwise you can prove that you have not entered anything by pressing the enter key. You will only have to confirm with the y key. If any of the information entered is wrong press n and enter the information.

Command:

sudo adduser bob --home /home/bob/

Output:

Adding user 'bob' ...
Adding new group 'bob' (1010) ...
Adding new user 'bob' (1010) with group 'bob' ...
Creating home directory '/home/bob/' ...
Copying files from '/etc/skel' ...
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Changing the user information for bob
Enter the new value, or press ENTER for the default
Full Name []:
Room Number []:
Work Phone []:
Home Phone []:
Other []:
Is the information correct? [Y/n] y

You will just have to modify bob by the name of the other users you have to created
To create a group follow the command below, you can modify groupname by the name of the group you want and 12345 by the desired gid

sudo addgroup groupname --gid 12345

Now to add a user to a group you have to use the command below in which you modify examplegroup by the name of the group in which you want to add your user and exampleusername by the user in question

sudo usermod -a -G examplegroup exampleusername

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Step 2

The purpose of this step is to assign administrator rights to the group you created earlier. For that we will modify the sudoers file with the command below.

sudo visudo

Then you will add this line to the file in the file. You can replace examplegroup with the group that will inherit the administrator rights.

%examplegroup ALL=(ALL) NOPASSWD:ALL

To leave the Document press the keys: ⌃X then ↩
If the list of keys to use is not displayed at the bottom of your screen you can try using this keystroke sequence: :q

if you want to test if the changes have taken place, you can use the following command by replacing username with the name of the account on which you want to change and test with the second command

su username
sudo apt-get install vim

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Step 3

In this step we will set up an RSA key. This key will allow us to connect to the machine without using a password.

Now the future steps will have to be executed on the machine that will want to connect to the server. First of all, we will have to generate a pair of keys, one private and one public. For this we need to execute the following command:

ssh-keygen

Output:

Generating public/private rsa key pair.
Enter file in which to save the key (/Users/charlescoste/.ssh/id_rsa):
/Users/charlescoste/.ssh/id_rsa already exists.
Overwrite (y/n)? y
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /Users/charlescoste/.ssh/id_rsa
Your public key has been saved in /Users/charlescoste/.ssh/id_rsa.pub
The key fingerprint is:
SHA256: Something local
The key's randomart image is:
Something

Then to initialize the connection you can write the following command replacing bob by the user on which the person must connect and 172.16.235.12 by the server ip

cat ~/.ssh/id_rsa.pub | ssh bob@172.16.235.12 "mkdir ~/.ssh -p && cat - >> ~/.ssh/authorized_keys"

Then to connect you should use this command replacing 172.16.235.12 by the server ip and bob by the server user

ssh bob@172.16.235.12

Now you are connected with ssh without password to the server

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Step 4

In this step we will install WordPress. First of all we have to install all the dependencies related to WordPress

sudo apt install apache2 \
                 ghostscript \
                 libapache2-mod-php \
                 mysql-server \
                 php \
                 php-bcmath \
                 php-curl \
                 php-imagick \
                 php-intl \
                 php-json \
                 php-mbstring \
                 php-mysql \
                 php-xml \
                 php-zip

Then we will create a folder for the server

sudo mkdir -p /srv/www

Then we will assign rights to the folder in question

sudo chown www-data: /srv/www

The following command will download the WordPress installation file and unzip it

curl https://wordpress.org/latest.tar.gz | sudo -u www-data tar zx -C /srv/www

Now the problem is that if we access the website we will see the default page of Apache (a web server creation tool). To display the WordPress configuration page we will have to initialize it. To do this we will open the web page file with the following command

nano /etc/apache2/sites-available/wordpress.conf

You will have to copy and paste the following code inside

<VirtualHost *:80>
    DocumentRoot /srv/www/wordpress
    <Directory /srv/www/wordpress>
        Options FollowSymLinks
        AllowOverride Limit Options FileInfo
        DirectoryIndex index.php
        Require all granted
    </Directory>
    <Directory /srv/www/wordpress/wp-content>
        Options FollowSymLinks
        Require all granted
    </Directory>
</VirtualHost>

Then we will start the server with this command

sudo a2ensite wordpress

Now we need to configure the WordPress related database. With this command we can access to MySQL

sudo mysql -u root

Here we create the database

CREATE DATABASE wordpress;

With this command we are going to create a MySQL user, you can replace your-password by a password

CREATE USER wordpress@localhost IDENTIFIED BY 'your-password';

After creating the user we will assign him the rights necessary for the operation of WordPress

GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP,ALTER
    -> ON wordpress.*
    -> TO wordpress@localhost;

The following command will reload the grant tables

FLUSH PRIVILEGES;

Finaly we quit the MySQL terminal

quit

and start MySQL

sudo service mysql start

And then all you have to do is access your server page using your browser. It will be necessary to configure your account then fill in the information of the database created earlier. And congratulations you have administered a linux system and installed WordPress. You can now create the site of your dreams.

Thank you for following this tutorial

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