Linux time machine

A few days ago my nextcloud server broke apart, completely. It had to be re-installed from scratch. I hadn’t realised that my backup wasn’t working, so I didn’t have a mysql dump. Luckily I still could mount the harddisk and rescue the /var/lib/mysql directory, with all the *.frm, *.ibd, etc. database files.

I re-installed the server and tried to simply copy the recovered database files over. Of course that didn’t work, because the database files were created with an older mariadb version. At least the error message said exactly what version they were created with. So I had to get the same version again, then I could spin up the database and do a mysqldump, which I then can re-import into the up-to-date mariadb again.

On a Debian system that’s basically impossible. Unless you’re lucky and a Debian release has exactly the version you need. You can get these older versions from previous releases or a newer version by enabling testing repositories. But even if you could get the version you need, if you’ve ever tried that, you know what a pain this is! Dependency hell!

But there’s Arch to the rescue! So I span up an Arch VM (see Vagrant file at the bottom). Went to the Arch archive: Arch Archive . Found the mariadb package of the specific version and noted the date when it was added. SSH’d into the Arch VM and adjusted the /etc/pacman.d/mirrorlist with the specific date URL e.g. Server=$repo/os/$arch. Then got the past keyring with pacman -S archlinux-keyring ca-certificates followed by a complete reset of the system to the past with pacman -Syyuu. And I had a linux system with the exact version of mariadb and all the necessary dependencies I wanted. Truely awesome! I don’t know of any other linux distribution which can do this!

Detailed instructions here: How to restore all packages to a specific date

Here’s a Vagrant file if you quickly wanna spin up an Arch VM:

Vagrant.configure("2") do |config| = "archlinux/archlinux" "private_network", ip: "", :name => 'vboxnet0', :adapter => 2

  config.vm.provider "virtualbox" do |vb| = "archy"
    vb.memory = "4096"
    vb.cpus = "2"

  config.vm.provision "shell", inline: <<-SHELL
    sed -i 's/PasswordAuthentication no/PasswordAuthentication yes/g' /etc/ssh/sshd_config
    echo 'MaxAuthTries 100' >> /etc/ssh/sshd_config
    systemctl restart sshd.service

You can then simply ssh into vagrant@ (this is using Virtualbox with a ‘vboxnet0’ host network setup); I don’t like the vagrant ssh workaround.