nixpkgs/nixos/modules/tasks/filesystems/zfs.nix
Ricardo M. Correia 6197fdc02d nixos/zfs: Refactor auto-snapshots and make them persistent
If you power off your machine frequently, you could miss the execution
of some snapshots.

This is more troublesome the more infrequently the snapshots are
triggered. For example, monthly snapshots only execute at exactly
midnight on the first day of the month.  If you only have your
machine powered on at that time with probability 50%, then half the
snapshots won't be triggered.

This means that if you wanted to keep 3 monthly snapshots, then instead
of keeping 3 months' worth of snapshotted data as you expected, you would
end up with snapshots spanning back 6 months.

Adding the "Persistent = yes" option to auto-snapshot timer units makes
a missed snapshot execute when booting up the machine.
2015-03-20 04:37:44 +01:00

349 lines
12 KiB
Nix

{ config, lib, pkgs, utils, ... }:
#
# todo:
# - crontab for scrubs, etc
# - zfs tunables
with utils;
with lib;
let
cfgSpl = config.boot.spl;
cfgZfs = config.boot.zfs;
cfgSnapshots = config.services.zfs.autoSnapshot;
cfgSnapFlags = cfgSnapshots.flags;
inInitrd = any (fs: fs == "zfs") config.boot.initrd.supportedFilesystems;
inSystem = any (fs: fs == "zfs") config.boot.supportedFilesystems;
enableAutoSnapshots = cfgSnapshots.enable;
enableZfs = inInitrd || inSystem || enableAutoSnapshots;
kernel = config.boot.kernelPackages;
splKernelPkg = if cfgZfs.useGit then kernel.spl_git else kernel.spl;
zfsKernelPkg = if cfgZfs.useGit then kernel.zfs_git else kernel.zfs;
zfsUserPkg = if cfgZfs.useGit then pkgs.zfs_git else pkgs.zfs;
autosnapPkg = pkgs.zfstools.override {
zfs = zfsUserPkg;
};
zfsAutoSnap = "${autosnapPkg}/bin/zfs-auto-snapshot";
datasetToPool = x: elemAt (splitString "/" x) 0;
fsToPool = fs: datasetToPool fs.device;
zfsFilesystems = filter (x: x.fsType == "zfs") (attrValues config.fileSystems);
isRoot = fs: fs.neededForBoot || elem fs.mountPoint [ "/" "/nix" "/nix/store" "/var" "/var/log" "/var/lib" "/etc" ];
allPools = unique ((map fsToPool zfsFilesystems) ++ cfgZfs.extraPools);
rootPools = unique (map fsToPool (filter isRoot zfsFilesystems));
dataPools = unique (filter (pool: !(elem pool rootPools)) allPools);
snapshotNames = [ "frequent" "hourly" "daily" "weekly" "monthly" ];
in
{
###### interface
options = {
boot.zfs = {
useGit = mkOption {
type = types.bool;
default = false;
example = true;
description = ''
Use the git version of the SPL and ZFS packages.
Note that these are unreleased versions, with less testing, and therefore
may be more unstable.
'';
};
extraPools = mkOption {
type = types.listOf types.str;
default = [];
example = [ "tank" "data" ];
description = ''
Name or GUID of extra ZFS pools that you wish to import during boot.
Usually this is not necessary. Instead, you should set the mountpoint property
of ZFS filesystems to <literal>legacy</literal> and add the ZFS filesystems to
NixOS's <option>fileSystems</option> option, which makes NixOS automatically
import the associated pool.
However, in some cases (e.g. if you have many filesystems) it may be preferable
to exclusively use ZFS commands to manage filesystems. If so, since NixOS/systemd
will not be managing those filesystems, you will need to specify the ZFS pool here
so that NixOS automatically imports it on every boot.
'';
};
forceImportRoot = mkOption {
type = types.bool;
default = true;
example = false;
description = ''
Forcibly import the ZFS root pool(s) during early boot.
This is enabled by default for backwards compatibility purposes, but it is highly
recommended to disable this option, as it bypasses some of the safeguards ZFS uses
to protect your ZFS pools.
If you set this option to <literal>false</literal> and NixOS subsequently fails to
boot because it cannot import the root pool, you should boot with the
<literal>zfs_force=1</literal> option as a kernel parameter (e.g. by manually
editing the kernel params in grub during boot). You should only need to do this
once.
'';
};
forceImportAll = mkOption {
type = types.bool;
default = true;
example = false;
description = ''
Forcibly import all ZFS pool(s).
This is enabled by default for backwards compatibility purposes, but it is highly
recommended to disable this option, as it bypasses some of the safeguards ZFS uses
to protect your ZFS pools.
If you set this option to <literal>false</literal> and NixOS subsequently fails to
import your non-root ZFS pool(s), you should manually import each pool with
"zpool import -f &lt;pool-name&gt;", and then reboot. You should only need to do
this once.
'';
};
};
services.zfs.autoSnapshot = {
enable = mkOption {
default = false;
type = types.bool;
description = ''
Enable the (OpenSolaris-compatible) ZFS auto-snapshotting service.
Note that you must set the <literal>com.sun:auto-snapshot</literal>
property to <literal>true</literal> on all datasets which you wish
to auto-snapshot.
You can override a child dataset to use, or not use auto-snapshotting
by setting its flag with the given interval:
<literal>zfs set com.sun:auto-snapshot:weekly=false DATASET</literal>
'';
};
flags = mkOption {
default = "-k -p";
example = "-k -p --utc";
type = types.str;
description = ''
Flags to pass to the zfs-auto-snapshot command.
Run <literal>zfs-auto-snapshot</literal> (without any arguments) to
see available flags.
If it's not too inconvenient for snapshots to have timestamps in UTC,
it is suggested that you append <literal>--utc</literal> to the list
of default options (see example).
Otherwise, snapshot names can cause name conflicts or apparent time
reversals due to daylight savings, timezone or other date/time changes.
'';
};
frequent = mkOption {
default = 4;
type = types.int;
description = ''
Number of frequent (15-minute) auto-snapshots that you wish to keep.
'';
};
hourly = mkOption {
default = 24;
type = types.int;
description = ''
Number of hourly auto-snapshots that you wish to keep.
'';
};
daily = mkOption {
default = 7;
type = types.int;
description = ''
Number of daily auto-snapshots that you wish to keep.
'';
};
weekly = mkOption {
default = 4;
type = types.int;
description = ''
Number of weekly auto-snapshots that you wish to keep.
'';
};
monthly = mkOption {
default = 12;
type = types.int;
description = ''
Number of monthly auto-snapshots that you wish to keep.
'';
};
};
};
###### implementation
config = mkMerge [
(mkIf enableZfs {
assertions = [
{
assertion = config.networking.hostId != null;
message = "ZFS requires config.networking.hostId to be set";
}
{
assertion = !cfgZfs.forceImportAll || cfgZfs.forceImportRoot;
message = "If you enable boot.zfs.forceImportAll, you must also enable boot.zfs.forceImportRoot";
}
];
boot = {
kernelModules = [ "spl" "zfs" ] ;
extraModulePackages = [ splKernelPkg zfsKernelPkg ];
};
boot.initrd = mkIf inInitrd {
kernelModules = [ "spl" "zfs" ];
extraUtilsCommands =
''
cp -v ${zfsUserPkg}/sbin/zfs $out/bin
cp -v ${zfsUserPkg}/sbin/zdb $out/bin
cp -v ${zfsUserPkg}/sbin/zpool $out/bin
cp -pdv ${zfsUserPkg}/lib/lib*.so* $out/lib
cp -pdv ${pkgs.zlib}/lib/lib*.so* $out/lib
'';
postDeviceCommands = concatStringsSep "\n" ([''
ZFS_FORCE="${optionalString cfgZfs.forceImportRoot "-f"}"
for o in $(cat /proc/cmdline); do
case $o in
zfs_force|zfs_force=1)
ZFS_FORCE="-f"
;;
esac
done
''] ++ (map (pool: ''
echo "importing root ZFS pool \"${pool}\"..."
zpool import -N $ZFS_FORCE "${pool}"
'') rootPools));
};
boot.loader.grub = mkIf inInitrd {
zfsSupport = true;
};
environment.etc."zfs/zed.d".source = "${zfsUserPkg}/etc/zfs/zed.d/*";
system.fsPackages = [ zfsUserPkg ]; # XXX: needed? zfs doesn't have (need) a fsck
environment.systemPackages = [ zfsUserPkg ]
++ optional enableAutoSnapshots autosnapPkg; # so the user can run the command to see flags
services.udev.packages = [ zfsUserPkg ]; # to hook zvol naming, etc.
systemd.packages = [ zfsUserPkg ];
systemd.services = let
getPoolFilesystems = pool:
filter (x: x.fsType == "zfs" && (fsToPool x) == pool) (attrValues config.fileSystems);
getPoolMounts = pool:
let
mountPoint = fs: escapeSystemdPath fs.mountPoint;
in
map (x: "${mountPoint x}.mount") (getPoolFilesystems pool);
createImportService = pool:
nameValuePair "zfs-import-${pool}" {
description = "Import ZFS pool \"${pool}\"";
requires = [ "systemd-udev-settle.service" ];
after = [ "systemd-udev-settle.service" "systemd-modules-load.service" ];
wantedBy = (getPoolMounts pool) ++ [ "local-fs.target" ];
before = (getPoolMounts pool) ++ [ "local-fs.target" ];
unitConfig = {
DefaultDependencies = "no";
};
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
};
script = ''
zpool_cmd="${zfsUserPkg}/sbin/zpool"
("$zpool_cmd" list "${pool}" >/dev/null) || "$zpool_cmd" import -N ${optionalString cfgZfs.forceImportAll "-f"} "${pool}"
'';
};
in listToAttrs (map createImportService dataPools) // {
"zfs-mount" = { after = [ "systemd-modules-load.service" ]; };
"zfs-share" = { after = [ "systemd-modules-load.service" ]; };
"zed" = { after = [ "systemd-modules-load.service" ]; };
};
systemd.targets."zfs-import" =
let
services = map (pool: "zfs-import-${pool}.service") dataPools;
in
{
requires = services;
after = services;
};
systemd.targets."zfs".wantedBy = [ "multi-user.target" ];
})
(mkIf enableAutoSnapshots {
systemd.services = let
descr = name: if name == "frequent" then "15 mins"
else if name == "hourly" then "hour"
else if name == "daily" then "day"
else if name == "weekly" then "week"
else if name == "monthly" then "month"
else throw "unknown snapshot name";
numSnapshots = name: builtins.getAttr name cfgSnapshots;
in builtins.listToAttrs (map (snapName:
{
name = "zfs-snapshot-${snapName}";
value = {
description = "ZFS auto-snapshotting every ${descr snapName}";
after = [ "zfs-import.target" ];
serviceConfig = {
Type = "oneshot";
ExecStart = "${zfsAutoSnap} ${cfgSnapFlags} ${snapName} ${toString (numSnapshots snapName)}";
};
restartIfChanged = false;
};
}) snapshotNames);
systemd.timers = let
timer = name: if name == "frequent" then "*:15,30,45" else name;
in builtins.listToAttrs (map (snapName:
{
name = "zfs-snapshot-${snapName}";
value = {
wantedBy = [ "timers.target" ];
timerConfig = {
OnCalendar = timer snapName;
Persistent = "yes";
};
};
}) snapshotNames);
})
];
}