nixpkgs/nixos/modules/services/backup/tarsnap.nix
Joachim Fasting 1bdd12ed69 nixos: refactor tarsnap backup service module
Major changes
- Port to systemd timers: for each archive configuration is created a
  tarsnap@archive-name.timer which triggers the instanced service unit
- Rename the `config` option to `archives`

Minor/superficial improvements
- Restrict tarsnap service capabilities
- Use dirOf builtin
- Set executable bit for owner of tarsnap cache directory
- Set IOSchedulingClass to idle
- Humanize numbers when printing stats
- Rewrite most option descriptions
- Simplify assertion
2015-03-10 12:35:58 +01:00

251 lines
8.2 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.services.tarsnap;
optionalNullStr = e: v: if e == null then "" else v;
configFile = cfg: ''
cachedir ${config.services.tarsnap.cachedir}
keyfile ${config.services.tarsnap.keyfile}
${optionalString cfg.nodump "nodump"}
${optionalString cfg.printStats "print-stats"}
${optionalString cfg.printStats "humanize-numbers"}
${optionalNullStr cfg.checkpointBytes "checkpoint-bytes "+cfg.checkpointBytes}
${optionalString cfg.aggressiveNetworking "aggressive-networking"}
${concatStringsSep "\n" (map (v: "exclude "+v) cfg.excludes)}
${concatStringsSep "\n" (map (v: "include "+v) cfg.includes)}
${optionalString cfg.lowmem "lowmem"}
${optionalString cfg.verylowmem "verylowmem"}
'';
in
{
options = {
services.tarsnap = {
enable = mkOption {
type = types.bool;
default = false;
description = ''
Enable periodic tarsnap backups.
'';
};
keyfile = mkOption {
type = types.str;
default = "/root/tarsnap.key";
description = ''
The keyfile which associates this machine with your tarsnap
account.
Create the keyfile with <command>tarsnap-keygen</command>.
The keyfile name should be given as a string and not a path, to
avoid the key being copied into the Nix store.
'';
};
cachedir = mkOption {
type = types.nullOr types.path;
default = "/var/cache/tarsnap";
description = ''
The cache allows tarsnap to identify previously stored data
blocks, reducing archival time and bandwidth usage.
Should the cache become desynchronized or corrupted, tarsnap
will refuse to run until you manually rebuild the cache with
<command>tarsnap --fsck</command>.
Set to <literal>null</literal> to disable caching.
'';
};
archives = mkOption {
type = types.attrsOf (types.submodule (
{
options = {
nodump = mkOption {
type = types.bool;
default = true;
description = ''
Exclude files with the <literal>nodump</literal> flag.
'';
};
printStats = mkOption {
type = types.bool;
default = true;
description = ''
Print global archive statistics upon completion.
The output is available via
<command>systemctl status tarsnap@archive-name</command>.
'';
};
checkpointBytes = mkOption {
type = types.nullOr types.str;
default = "1GB";
description = ''
Create a checkpoint every <literal>checkpointBytes</literal>
of uploaded data (optionally specified using an SI prefix).
1GB is the minimum value. A higher value is recommended,
as checkpointing is expensive.
Set to <literal>null</literal> to disable checkpointing.
'';
};
period = mkOption {
type = types.str;
default = "01:15";
example = "hourly";
description = ''
Create archive at this interval.
The format is described in
<citerefentry><refentrytitle>systemd.time</refentrytitle>
<manvolnum>7</manvolnum></citerefentry>.
'';
};
aggressiveNetworking = mkOption {
type = types.bool;
default = false;
description = ''
Upload data over multiple TCP connections, potentially
increasing tarsnap's bandwidth utilisation at the cost
of slowing down all other network traffic. Not
recommended unless TCP congestion is the dominant
limiting factor.
'';
};
directories = mkOption {
type = types.listOf types.path;
default = [];
description = "List of filesystem paths to archive.";
};
excludes = mkOption {
type = types.listOf types.str;
default = [];
description = ''
Exclude files and directories matching these patterns.
'';
};
includes = mkOption {
type = types.listOf types.str;
default = [];
description = ''
Include only files and directories matching these
patterns (the empty list includes everything).
Exclusions have precedence over inclusions.
'';
};
lowmem = mkOption {
type = types.bool;
default = false;
description = ''
Reduce memory consumption by not caching small files.
Possibly beneficial if the average file size is smaller
than 1 MB and the number of files is lower than the
total amount of RAM in KB.
'';
};
verylowmem = mkOption {
type = types.bool;
default = false;
description = ''
Reduce memory consumption by a factor of 2 beyond what
<literal>lowmem</literal> does, at the cost of significantly
slowing down the archiving process.
'';
};
};
}
));
default = {};
example = literalExample ''
{
nixos =
{ directories = [ "/home" "/root/ssl" ];
};
gamedata =
{ directories = [ "/var/lib/minecraft "];
period = "*:30";
};
}
'';
description = ''
Tarsnap archive configurations. Each attribute names an archive
to be created at a given time interval, according to the options
associated with it. When uploading to the tarsnap server,
archive names are suffixed by a 1 second resolution timestamp.
For each member of the set is created a timer which triggers the
instanced <literal>tarsnap@</literal> service unit. You may use
<command>systemctl start tarsnap@archive-name</command> to
manually trigger creation of <literal>archive-name</literal> at
any time.
'';
};
};
};
config = mkIf cfg.enable {
assertions =
(mapAttrsToList (name: cfg:
{ assertion = cfg.directories != [];
message = "Must specify paths for tarsnap to back up";
}) cfg.archives) ++
(mapAttrsToList (name: cfg:
{ assertion = !(cfg.lowmem && cfg.verylowmem);
message = "You cannot set both lowmem and verylowmem";
}) cfg.archives);
systemd.services."tarsnap@" = {
description = "Tarsnap archive '%i'";
requires = [ "network.target" ];
path = [ pkgs.tarsnap pkgs.coreutils ];
scriptArgs = "%i";
script = ''
mkdir -p -m 0755 ${dirOf cfg.cachedir}
mkdir -p -m 0700 ${cfg.cachedir}
DIRS=`cat /etc/tarsnap/$1.dirs`
exec tarsnap --configfile /etc/tarsnap/$1.conf -c -f $1-$(date +"%Y%m%d%H%M%S") $DIRS
'';
serviceConfig = {
IOSchedulingClass = "idle";
NoNewPrivileges = "true";
CapabilityBoundingSet = "CAP_DAC_READ_SEARCH";
};
};
systemd.timers = mapAttrs' (name: cfg: nameValuePair "tarsnap@${name}"
{ timerConfig.OnCalendar = cfg.period;
wantedBy = [ "timers.target" ];
}) cfg.archives;
environment.etc =
(mapAttrs' (name: cfg: nameValuePair "tarsnap/${name}.conf"
{ text = configFile cfg;
}) cfg.archives) //
(mapAttrs' (name: cfg: nameValuePair "tarsnap/${name}.dirs"
{ text = concatStringsSep " " cfg.directories;
}) cfg.archives);
environment.systemPackages = [ pkgs.tarsnap ];
};
}