110 lines
3.9 KiB
Nix
110 lines
3.9 KiB
Nix
{ config, lib, utils, pkgs, ... }:
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let
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inherit (lib) escapeShellArg optionalString concatStringsSep
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nameValuePair mapAttrs' filterAttrs mapAttrsToList
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mkIf mkOption types;
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inherit (utils) escapeSystemdPath;
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# (wip) more configurable than old one, will be used by volatile btrfs module
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genBtrfsInit' = fsConfig: genBtrfsInit {
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inherit (fsConfig) device;
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inherit (fsConfig.btrfs) subvolume;
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inherit (fsConfig.btrfs.cleanOnBoot) destination;
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};
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genBtrfsInit = { subvolume, device, destination, }:
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''
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mkdir -p /btrfs_tmp
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mount ${escapeShellArg device} /btrfs_tmp -o subvol=/
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# ensure subvol parent directory exists
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mkdir -p $(dirname /btrfs_tmp/${escapeShellArg subvolume})
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if [[ -e /btrfs_tmp/${escapeShellArg subvolume} ]] ; then
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mkdir -p /btrfs_tmp/${escapeShellArg destination}
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timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp/${escapeShellArg subvolume})" "+%Y-%m-%-d_%H:%M:%S")
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mv /btrfs_tmp/${escapeShellArg subvolume} /btrfs_tmp/${escapeShellArg destination}/"$timestamp"
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fi
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btrfs subvolume create /btrfs_tmp/${escapeShellArg subvolume}
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umount /btrfs_tmp
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'';
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# TODO implement deletion once system is booted. the old implementation did
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# it here, which is not safe until system time is at least monotonic.
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# systemd tmpfiles is good enough, just mount it to somewhere in /run
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generateInitrdUnit = name: values: let
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deviceUnit = "${escapeSystemdPath values.device}.device";
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in nameValuePair "btrfs-clean-subvolume-${escapeSystemdPath name}" {
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description = "BTRFS subvolume reset for ${name} mountpoint";
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wantedBy = [ "initrd-root-fs.target" ];
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before = [ "sysroot.mount" ];
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after = [ deviceUnit ];
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requires = [ deviceUnit ];
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serviceConfig = {
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Type = "oneshot";
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RemainAfterExit = true;
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Exec = pkgs.writeShellScript "btrfs-clean-subvolume" (genBtrfsInit' values);
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};
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};
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fsModule = { config, name, ... }:
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{
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options.btrfs = {
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subvolume = mkOption {
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description = "btrfs subvolume of filesystem";
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type = with types; nullOr path;
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default = null;
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};
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cleanOnBoot = {
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enable = mkOption {
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description = ''
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Whether to replace this subvolume with an empty one before mount.
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This is useful in combination with Impermanence.
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'';
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type = types.bool;
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default = false;
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example = true;
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};
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destination = mkOption {
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description = ''
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Destination of old subvolume, relative to btrfs root (subvol=/).
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Cleanup is handled as a separate step, in case any old state is
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needed.
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'';
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type = types.path;
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example = "/old_roots";
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};
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};
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};
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config = {
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options = let
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inherit (config.btrfs) subvolume;
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in lib.mkIf (!(isNull subvolume)) [ "subvol=${subvolume}" ];
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};
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};
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in
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{
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options = {
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fileSystems = mkOption {
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type = with types; attrsOf (submodule fsModule);
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};
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};
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config = let
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configuredFileSystems = filterAttrs (k: v: v.btrfs.cleanOnBoot.enable) config.fileSystems;
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in mkIf (configuredFileSystems != { }) {
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# assertions = mapAttrsToList (name: values:
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# { assertion = (!(isNull values.btrfs.subvolume));
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# message = "`fileSystems.${name}.btrfs.cleanOnBoot.enabled` is set to true, but `filesystems.${name}.btrfs.subvolume` is not set."; }) configuredFileSystems;
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# assertions = [{ assertion = false; message = "btrfs-clean.nix: fix this assertion. look at nixos/modules/system/boot/luksroot preOpenCommands assertion for inspiration."; }];
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boot.initrd.systemd.services = mapAttrs' generateInitrdUnit configuredFileSystems;
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boot.initrd.postDeviceCommands = let
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scripts = mapAttrsToList (name: values: genBtrfsInit' values) configuredFileSystems;
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in mkIf (!config.boot.initrd.systemd.enable) (lib.mkAfter (concatStringsSep "\n" scripts));
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};
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}
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