Drupal 8.5.4 all links give 404 Not Found

Question

I am using Ubuntu 18.04 server and Drupal 8.5.4. The installation was successful.I can login and my home page is displayed . But any other url on the page gives error. One such

Answer 1

Now, Need to activate mod_rewrite:

sudo a2enmod rewrite

This will activate the module or alert you that the module is already in effect. To put these changes into effect, restart Apache:

sudo service apache2 restart

Answer 2

There are two things

1: Ensure that mod_rewrite is enabled To check this create a file called phpinfo.php in the root of your site. This file should be accessible from a web browser and contain this code:

phpinfo();

Navigate to phpinfo.php in a browser like this: http://www.example.com/phpinfo.php

On that page, look for a section called "Loaded Modules" and check that mod_rewrite is included. If not, mod_rewrite is not being loaded by apache and will need to be enabled. To enable this mode just write the following command in terminal and restart the apache

sudo a2enmod rewrite

2:Ensure that Drupal's .htaccess file is being used Once it's been confirmed that mod_rewrite is enabled, double check that Drupal's .htaccess file is in the site's root, and that it is working. Confirm that .htaccess is enabled by temporarily replacing Drupal's .htaccess file. Make a backup of the existing .htaccess and create one like this

DirectoryIndex phpinfo.php

Now try the site URL without specifing a page or file in a web browser: http://www.example.com/. If you see PHP's phpinfo dump, the .htaccess file worked and you can restore the old one. If not, the server may not be allowing .htaccess overrides for your site.To allow this edit you virtual hosting file or apache2.conf file. For apache2.conf file change

<Directory /var/www/>
    Options Indexes FollowSymLinks
    AllowOverride None        

to

<Directory /var/www/>
        Options Indexes FollowSymLinks
        AllowOverride All

Restart the apache and hopefully site works well

Answer 3

I changed 

<Directory /var/www/>
        Options Indexes FollowSymLinks
        AllowOverride None
        Require all granted

to 

<Directory /var/www/>
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted

in /etc/apache2/apach2.conf , restarted Apache with service apache2 restart