nixos-config/machines/fuuko/services/media-backup.nix

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2021-04-16 17:13:46 +02:00
# This creates a backup of my media files when a specific hard drive is
# hotplugged. The hard drive has a btrfs filesystem inside of a luks container.
# The filesystem can be created with commands similar to this:
# cryptsetup luksFormat --label="fuuko-media-backup-luks" --key-file=/path/to/key /dev/sdb
# mkfs.btrfs -L "fuuko-media-backup" /dev/mapper/media-backup
{ lib, pkgs, ... }:
let
baseDir = "/data/media";
mountPoint = "/mnt/media-backup";
in
{
# Systemd mount units do not support cryptsetup
systemd.services.media-backup-luks = {
after = [ ''dev-disk-by\x2dlabel-fuuko\x2dmedia\x2dbackup\x2dluks.device'' ];
bindsTo = [ ''dev-disk-by\x2dlabel-fuuko\x2dmedia\x2dbackup\x2dluks.device'' ];
unitConfig = {
StopWhenUnneeded = true;
};
serviceConfig = {
Type = "oneshot";
RemainAfterExit = "yes";
ExecStart = "${pkgs.cryptsetup}/bin/cryptsetup open --type luks2 --key-file=${baseDir}/.backup-key /dev/disk/by-label/fuuko-media-backup-luks media-backup";
ExecStop = "${pkgs.cryptsetup}/bin/cryptsetup close media-backup";
};
};
systemd.mounts = lib.singleton {
after = [ "media-backup-luks.service" ];
bindsTo = [ "media-backup-luks.service" ];
unitConfig = {
StopWhenUnneeded = true;
};
what = "/dev/mapper/media-backup";
where = mountPoint;
};
systemd.services.media-backup = {
wantedBy = [ ''dev-disk-by\x2dlabel-fuuko\x2dmedia\x2dbackup\x2dluks.device'' ];
unitConfig = {
RequiresMountsFor = "/mnt/media-backup";
};
script = ''
${pkgs.rsync}/bin/rsync \
--archive \
--delete \
--links \
--partial \
--recursive\
--verbose \
${lib.escapeShellArg baseDir} \
${lib.escapeShellArg mountPoint}
'';
serviceConfig = {
IOSchedulingClass = "best-effort";
IOSchedulingPriority = 7;
Nice = 10;
};
};
}