====== How to migrate a (web) server ======
This guide explains the steps to take when migrating a web server to a new machine and/or a new platform. Most of it will also apply to any other type of server.

===== Prerequisites =====
  * Source (Pandora): running existing server with Debian 9 installed
  * Destination (Calypso): basic install of the new server with Debian 11
  * A firewall (FW) with port forwards for outside access (e.g. ports 80 and 443)
  * Make sure both machines have [[deb9:ssh#linux_host|SSH access]] through a private key so you don't need to enter a password
  * Create a batch file ''ccalypso'' on Pandora to facilitate copying folders and files with the following content:<code>#!/bin/bash
if [ "$2" == "" ]; then
    exit 1
fi
sudo rsync -avz -e 'ssh -i /home/user/.ssh/id_ecdsa -p 22' --rsync-path='sudo rsync' $1 user@dest.ip.addr:$2</code>

===== User home directory =====
  - Copy folders and files from Pandora<code>$ ccalypso /home/user/folder-or-file /home/user/</code>
  - If the UID on both machines are the same you don't need to update folder and file ownership
  - You can use the same way for any other folder or file you want to transfer from the old to the new server

===== Apache 2.4 =====
  - Install [[deb11:apache|Apache 2.4 and PHP 7/8]] on Calypso
  - Rename folders on Calypso<code>$ sudo mv /etc/apache2/conf-available /etc/apache2/conf-available-debian
$ sudo mv /etc/apache2/conf-enabled /etc/apache2/conf-enabled-debian
$ sudo mv /etc/apache2/sites-available /etc/apache2/sites-available-debian
$ sudo mv /etc/apache2/sites-enabled /etc/apache2/sites-enabled-debian</code>
  - Copy folders from Pandora<code>$ ccalypso /etc/apache2/conf-available /etc/apache2/
$ ccalypso /etc/apache2/conf-enabled /etc/apache2/
$ ccalypso /etc/apache2/sites-available /etc/apache2/
$ ccalypso /etc/apache2/sites-enabled /etc/apache2/</code>
  - On Calypso check and copy selected files back from the debian installed folder to the folder copied from Pandora
  - If the UID on both machines are the same you don't need to update folder and file ownership
  - If you have reverse proxies don't forget to update your firewall settings

===== MariaDB =====
  - Install [[deb11:mariadb|MariaDB 10.5]] on Calypso
  - On Calypso, dump the contents of the ''mysql'' database<code>$ mysqldump -u user -p --opt mysql > mysql.sql</code>
  - Stop the mysql service on both machines<code>$ sudo service mysql stop</code>
  - On Calypso, rename the db folder<code>$ sudo mv /var/lib/mysql /var/lib/mysql_debian</code>
  - On Pandora, copy the db folder to Calypso<code>$ ccalypso /var/lib/mysql /var/lib/</code>
  - On Calypso, remove the following folders and files<code>$ sudo rm -R /var/lib/mysql/mysql
$ sudo rm -R /var/lib/mysql/phpmyadmin
$ sudo rm -R /var/lib/mysql/debian-10.1.flag</code>
  - On Calypso move the following folders and files back from the ''mysql_debian'' folder to the ''mysql'' folder copied from Pandora<code>$ sudo mv /var/lib/mysql_debian/mysql /var/lib/mysql
$ sudo mv /var/lib/mysql_debian/aria_log00000001 /var/lib/mysql
$ sudo mv /var/lib/mysql_debian/aria_log_control /var/lib/mysql
$ sudo mv /var/lib/mysql_debian/debian-10.5.flag /var/lib/mysql
$ sudo mv /var/lib/mysql_debian/multi-master.info /var/lib/mysql
$ sudo mv /var/lib/mysql_debian/mysql_upgrade_info /var/lib/mysql</code>
  - Remove folder ''/var/lib/mysql_debian''
  - If the UID on both machines are the same you don't need to update folder and file ownership

===== System =====
  - Check and adjust crontab for all users and root
  - Check and adjust the sudoers file and all files in ''/etc/sudoers.d/''
  - Check other machines which depend on the webserver, for example a mail server using Let's Encrypt certificates managed by the web server