Debian Buster: install and configure phpmyadmin

Required Apache2, Mysql/MariaDB,  and PHP 7.x

There is no phpmyadmin package in Debian 10 Buster Repository. You need to install it manually.

1. Create folder /usr/share/phpmyadmin/
2. Download phpmyadmin from https://www.phpmyadmin.net/downloads/ and extract into  /usr/share/phpmyadmin/. Note: phpMyAdmin version 4.9.1.
3. Create folder /etc/phpmyadmin/
4. Create a new config file from configuration using file config.sample.inc.php
   # cp /usr/share/phpmyadmin/config.sample.inc.php /etc/phpmyadmin/config.inc.php
5. Create folder /var/lib/phpmyadmin/tmp
   # mkdir /var/lib/phpmyadmin/tmp
6. Edit /etc/phpmyadmin/config.inc.php
   $cfg['blowfish_secret'] = 'ABCDEabcde1234567890ABCDEfghij12'; // random 32 characters
   ...
   /**
    * Directories for saving/loading files from server
    */
   $cfg['UploadDir'] = '/var/lib/phpmyadmin/tmp';
   $cfg['SaveDir'] = '/var/lib/phpmyadmin/tmp';
7. Create apache configuration file for phpmyadmin
   # touch /etc/apache2/conf-available/phpmyadmin.conf
8. Edit /etc/apache2/conf-available/phpmyadmin.conf, copy paste these lines.
   Alias /phpmyadmin /usr/share/phpmyadmin
   
   <Directory /usr/share/phpmyadmin>
       Options SymLinksIfOwnerMatch
       DirectoryIndex index.php
   
       <IfModule mod_php5.c>
           <IfModule mod_mime.c>
               AddType application/x-httpd-php .php
           </IfModule>
           <FilesMatch ".+\.php$">
               SetHandler application/x-httpd-php
           </FilesMatch>
   
           php_value include_path .
           php_admin_value upload_tmp_dir /var/lib/phpmyadmin/tmp
           php_admin_value open_basedir /usr/share/phpmyadmin/:/etc/phpmyadmin/:/var/lib/phpmyadmin/:/usr/share/php/php-gettext/:/usr/share/php/php-php-gettext/:/usr/share/javascript/:/usr/share/php/tcpdf/:/usr/share/doc/phpmyadmin/:/usr/share/php/phpseclib/
           php_admin_value mbstring.func_overload 0
       </IfModule>
       <IfModule mod_php.c>
           <IfModule mod_mime.c>
               AddType application/x-httpd-php .php
           </IfModule>
           <FilesMatch ".+\.php$">
               SetHandler application/x-httpd-php
           </FilesMatch>
   
           php_value include_path .
           php_admin_value upload_tmp_dir /var/lib/phpmyadmin/tmp
           php_admin_value open_basedir /usr/share/phpmyadmin/:/etc/phpmyadmin/:/var/lib/phpmyadmin/:/usr/share/php/php-gettext/:/usr/share/php/php-php-gettext/:/usr/share/javascript/:/usr/share/php/tcpdf/:/usr/share/doc/phpmyadmin/:/usr/share/php/phpseclib/
           php_admin_value mbstring.func_overload 0
       </IfModule>
   
   </Directory>
   
   # Authorize for setup
   <Directory /usr/share/phpmyadmin/setup>
       <IfModule mod_authz_core.c>
           <IfModule mod_authn_file.c>
               AuthType Basic
               AuthName "phpMyAdmin Setup"
               AuthUserFile /etc/phpmyadmin/htpasswd.setup
           </IfModule>
           Require valid-user
       </IfModule>
   </Directory>
   
   # Disallow web access to directories that don't need it
   <Directory /usr/share/phpmyadmin/templates>
       Require all denied
   </Directory>
   <Directory /usr/share/phpmyadmin/libraries>
       Require all denied
   </Directory>
   <Directory /usr/share/phpmyadmin/setup/lib>
       Require all denied
   </Directory>
9. Enabling your phpmyadmin config in apache2
   # a2enconf phpmyadmin
   Note to disable # a2disconf phpmyadmin
10. Reload/restart your apache2
    # systemctl reload apache2

Remove folder /usr/share/phpmyadmin/test/ and /usr/share/phpmyadmin/setup/. You can access your phpmyadmin using http://localhost/phpmyadmin.

If your mysql root (with password) can not login with error:
mysqli_real_connect(): (HY000/1698): Access denied for user 'root'@'localhost', do these:

1. using cli connect to mysql
   # mysql -u root -p
   Enter password:
2. Select mysql database
    > use mysql;
   Reading table information for completion of table and column names
   You can turn off this feature to get a quicker startup with -A
   
   Database changed
3. Change root plugin from unix_socket to mysql_native_password
   > update user set plugin='mysql_native_password' where user='root';
   Query OK, 1 row affected (1.372 sec)
   Rows matched: 1  Changed: 1  Warnings: 0
4. restart your mysql
   # systemctl restart mysql

If something goes wrong after you change unix_socket to mysql_native_password, revert it back.

Stop mysql server

# systemctl stop mysql

Start your mysql using mysqld_safe

# mysqld_safe --skip-grant-tables

In other terminal connect to mysql using root user

# mysql -u root
MariaDB [(none)]> user mysql;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'user mysql' at line 1
MariaDB [(none)]> use mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [mysql]> update user set plugin='unix_socket' where user='root';
\q


Now, You may kill your terminal where mysqld_safe running and start your mysql service normally.

References:

1. https://docs.phpmyadmin.net/en/latest/setup.html
2. https://salsa.debian.org/phpmyadmin-team/phpmyadmin/blob/master/debian/README.Debian
3. https://computingforgeeks.com/install-phpmyadmin-with-apache-on-debian-10-buster/
4. https://docs.phpmyadmin.net/en/latest/config.html#config
5. https://askubuntu.com/questions/998920/1698-access-denied-for-user-rootlocalhost-mysql-5-7-and-ubuntu-16-04