What is swappiness and how do I change it?

    The swappiness parameter controls the tendency of the kernel to move processes out of physical memory and onto the swap disk. Because disks are much slower than RAM, this can lead to slower response times for system and applications if processes are too aggressively moved out of memory.

        swappiness can have a value of between 0 and 100

        swappiness=0 tells the kernel to avoid swapping processes out of physical memory for as long as possible. For Kernel version 3.5 and newer it disables swapiness.

        swappiness=100 tells the kernel to aggressively swap processes out of physical memory and move them to swap cache

    The default setting in Ubuntu is swappiness=60. Reducing the default value of swappiness will probably improve overall performance for a typical Ubuntu desktop installation. A value of swappiness=10 is recommended, but feel free to experiment. Note: Ubuntu server installations have different performance requirements to desktop systems, and the default value of 60 is likely more suitable.

    To check the swappiness value

    cat /proc/sys/vm/swappiness

    To change the swappiness value A temporary change (lost on reboot) with a swappiness value of 10 can be made with

    sudo sysctl vm.swappiness=10

    To make a change permanent, edit the configuration file with your favorite editor:

    gksudo gedit /etc/sysctl.conf

    Search for vm.swappiness and change its value as desired. If vm.swappiness does not exist, add it to the end of the file like so:

    vm.swappiness=10

    Save the file and reboot.

bash

prepare the new server, make a new installation of the very same version of ISPConfig you have on the origin server;
    make sure you have the same php packages installed on the new server. You can generate a list on the origin server with
    dpkg --get-selections | grep ^php | awk '{print $1}' | xargs
    and paste the output to apt install on the destination;
    make a backup of the ispconfig database on origin. If you want you can change the IP (and eventually the hostname) with sed:
    sed -i 's/1\.2\.3\.4/5\.6\.7\.8/g' db-dbispconfig-2019-05-25.sql
    sed -i 's/old\.host\.name/new\.host\.name/g' db-dbispconfig-2019-05-25.sql
    And restore it on the destination with:
    cat db-dbispconfig-2019-05-25.sql | mysql -u root -p dbispconfig
    connect to the new server ispconfig panel and go to Tools > Resync, check the All services checkbox and press Start;
    rsync /var/www with:
    rsync -a --stats --progress --delete ORIGIN_SERVER:/var/www/* /var/www/
    rsync /var/vmail by adjusting the command above
    rsync /etc/letsencrypt
    rsync -a --stats --progress --delete ORIGIN_SERVER:/etc/letsencrypt/* /etc/letsencrypt/
    make a dump of all c* databases and restore them on the new server;
    if you want to retain the same ISPConfig panel certs copy /usr/local/ispconfig/interface/ssl/;
    move DNS and all related stuff to the new IP.