mysqlBackup service: let it work with default settings

* Grants enough privileges to the configured user so that it can run
  mysqldump.

* Adds a nixos test.

* Use systemd timers instead of a cronjob (by @fadenb).

* Creates a new user for backups by default, instead of using mysql
  user.

* Ensures that backup user has write permissions on backup location.

* Write backup to a temporary file before renaming so that a failed
  backup won't overwrite the previous backup, and so that the backup
  location will never contain a partial backup.

Breaking changes:

 * Renamed period to calendar to reflect the change in how to
   configure the backup time.

 * A failed backup will no longer result in cron sending an e-mail --
   users' monitoring systems must be updated.

Resolves #24728

1 files changed, 1 insertions, 0 deletions

diff --git a/nixos/release.nix b/nixos/release.nix
index ac7755a160f4..06f1c73410c0 100644
--- a/nixos/release.nix
+++ b/nixos/release.nix
@@ -283,6 +283,7 @@ in rec {
   tests.mumble = callTest tests/mumble.nix {};
   tests.munin = callTest tests/munin.nix {};
   tests.mysql = callTest tests/mysql.nix {};
+  tests.mysqlBackup = callTest tests/mysql-backup.nix {};
   tests.mysqlReplication = callTest tests/mysql-replication.nix {};
   tests.nat.firewall = callTest tests/nat.nix { withFirewall = true; };
   tests.nat.firewall-conntrack = callTest tests/nat.nix { withFirewall = true; withConntrackHelpers = true; };