nixos-servers/nixos/modules/backups.nix

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{ pkgs, lib, config, ... }:
let
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cfg = config.lab.backups;
snapshotFile = "/tmp/snapshot.qcow2";
snapshotMount = "/tmp/snapshot";
beforeEverything = pkgs.writeShellScriptBin "beforeEverything" ''
${pkgs.libvirt}/bin/virsh snapshot-create-as --domain ${cfg.domainName} --name backup-${cfg.domainName} --disk-only --quiesce --no-metadata --diskspec vda,snapshot=no --diskspec vdb,file=${snapshotFile} && ${pkgs.coreutils}/bin/sleep 1
${pkgs.coreutils}/bin/mkdir -p ${snapshotMount}
${pkgs.libguestfs-with-appliance}/bin/guestmount -a ${snapshotFile} -m /dev/sda1 --ro ${snapshotMount}
'';
afterEverything = pkgs.writeShellScriptBin "afterEverything" ''
set +e
${pkgs.coreutils}/bin/sleep 10
${pkgs.libguestfs-with-appliance}/bin/guestunmount ${snapshotMount} && ${pkgs.coreutils}/bin/sleep 1
${pkgs.coreutils}/bin/rm -rf ${snapshotMount}
${pkgs.libvirt}/bin/virsh blockcommit ${cfg.domainName} vdb --active --verbose --pivot
${pkgs.coreutils}/bin/rm -f ${snapshotFile}
'';
borgmaticConfig = pkgs.writeTextFile {
name = "borgmatic-config";
text = ''
source_directories:
- ${snapshotMount}
repositories:
- path: ${cfg.repoLocation}
label: ${cfg.domainName}
keep_daily: 7
keep_weekly: 4
keep_monthly: 6
unknown_unencrypted_repo_access_is_ok: true
before_everything:
- ${beforeEverything}/bin/beforeEverything
after_everything:
- ${afterEverything}/bin/afterEverything
'';
};
in
{
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options.lab.backups = {
enable = lib.mkOption {
default = false;
type = lib.types.bool;
description = ''
Whether to enable backups of persistent data on this machine.
'';
};
repoLocation = lib.mkOption {
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default = "${config.lab.dataDisk.mountPoint}/backups/thecloud-data.borg";
type = lib.types.str;
description = ''
Location of the Borg repository to back up to.
'';
};
domainName = lib.mkOption {
default = "thecloud";
type = lib.types.str;
description = ''
The name of the Libvirt domain with the data disk attached.
'';
};
};
config = lib.mkIf cfg.enable {
environment.systemPackages = with pkgs; [ libguestfs-with-appliance borgbackup ];
# Converted from:
# https://github.com/borgmatic-collective/borgmatic/tree/84823dfb912db650936e3492f6ead7e0e0d32a0f/sample/systemd
systemd.services.borgmatic = {
description = "borgmatic backup";
wants = [ "network-online.target" ];
after = [ "network-online.target" ];
unitConfig = {
ConditionACPower = true;
};
serviceConfig = {
Type = "oneshot";
Nice = 19;
CPUSchedulingPolicy = "batch";
IOSchedulingClass = "best-effort";
IOSchedulingPriority = 7;
IOWeight = 100;
Restart = "no";
LogRateLimitIntervalSec = 0;
};
preStart = "${pkgs.coreutils}/bin/sleep 1m";
script = "${pkgs.systemd}/bin/systemd-inhibit --who=\"borgmatic\" --what=\"sleep:shutdown\" --why=\"Prevent interrupting scheduled backup\" ${pkgs.borgmatic}/bin/borgmatic --verbosity -2 --syslog-verbosity 1";
};
environment.etc."borgmatic/config.yaml" = {
source = borgmaticConfig;
};
# systemd.timers.borgmatic = {
# description = "Run borgmatic backup";
# wantedBy = [ "timers.target" ];
# timerConfig = {
# OnCalendar = "*-*-* 3:00:00";
# Persistent = true;
# RandomizedDelaySec = "3h";
# };
# };
};
}