diff --git a/btrbk-patched/default.nix b/btrbk-patched/default.nix
new file mode 100644
index 0000000..13528db
--- /dev/null
+++ b/btrbk-patched/default.nix
@@ -0,0 +1,273 @@
+{ config, pkgs, lib, ... }:
+let
+  inherit (lib)
+    concatLists
+    concatMap
+    concatMapStringsSep
+    concatStringsSep
+    filterAttrs
+    isAttrs
+    literalExpression
+    mapAttrs'
+    mapAttrsToList
+    mkIf
+    mkOption
+    optionalString
+    sort
+    types
+    ;
+
+  # The priority of an option or section.
+  # The configurations format are order-sensitive. Pairs are added as children of
+  # the last sections if possible, otherwise, they start a new section.
+  # We sort them in topological order:
+  # 1. Leaf pairs.
+  # 2. Sections that may contain (1).
+  # 3. Sections that may contain (1) or (2).
+  # 4. Etc.
+  prioOf = { name, value }:
+    if !isAttrs value then 0 # Leaf options.
+    else {
+      target = 1; # Contains: options.
+      subvolume = 2; # Contains: options, target.
+      volume = 3; # Contains: options, target, subvolume.
+    }.${name} or (throw "Unknow section '${name}'");
+
+  genConfig' = set: concatStringsSep "\n" (genConfig set);
+  genConfig = set:
+    let
+      pairs = mapAttrsToList (name: value: { inherit name value; }) set;
+      sortedPairs = sort (a: b: prioOf a < prioOf b) pairs;
+    in
+      concatMap genPair sortedPairs;
+  genSection = sec: secName: value:
+    [ "${sec} ${secName}" ] ++ map (x: " " + x) (genConfig value);
+  genPair = { name, value }:
+    if !isAttrs value
+    then [ "${name} ${value}" ]
+    else concatLists (mapAttrsToList (genSection name) value);
+
+  sudo_doas =
+    if config.security.sudo.enable then "sudo"
+    else if config.security.doas.enable then "doas"
+    else throw "The btrbk nixos module needs either sudo or doas enabled in the configuration";
+
+  addDefaults = settings: { backend = "btrfs-progs-${sudo_doas}"; } // settings;
+
+  mkConfigFile = name: settings: pkgs.writeTextFile {
+    name = "btrbk-${name}.conf";
+    text = genConfig' (addDefaults settings);
+    checkPhase = ''
+      set +e
+      ${pkgs.btrbk}/bin/btrbk -c $out dryrun
+      # According to btrbk(1), exit status 2 means parse error
+      # for CLI options or the config file.
+      if [[ $? == 2 ]]; then
+        echo "Btrbk configuration is invalid:"
+        cat $out
+        exit 1
+      fi
+      set -e
+    '';
+  };
+
+  cfg = config.services.btrbk-patched;
+  sshEnabled = cfg.sshAccess != [ ];
+  serviceEnabled = cfg.instances != { };
+in
+{
+  meta.maintainers = with lib.maintainers; [ oxalica ];
+
+  options = {
+    services.btrbk-patched = {
+      extraPackages = mkOption {
+        description = lib.mdDoc "Extra packages for btrbk, like compression utilities for `stream_compress`";
+        type = types.listOf types.package;
+        default = [ ];
+        example = literalExpression "[ pkgs.xz ]";
+      };
+      niceness = mkOption {
+        description = lib.mdDoc "Niceness for local instances of btrbk. Also applies to remote ones connecting via ssh when positive.";
+        type = types.ints.between (-20) 19;
+        default = 10;
+      };
+      ioSchedulingClass = mkOption {
+        description = lib.mdDoc "IO scheduling class for btrbk (see ionice(1) for a quick description). Applies to local instances, and remote ones connecting by ssh if set to idle.";
+        type = types.enum [ "idle" "best-effort" "realtime" ];
+        default = "best-effort";
+      };
+      instances = mkOption {
+        description = lib.mdDoc "Set of btrbk instances. The instance named `btrbk` is the default one.";
+        type = with types;
+          attrsOf (
+            submodule {
+              options = {
+                onCalendar = mkOption {
+                  type = types.nullOr types.str;
+                  default = "daily";
+                  description = lib.mdDoc ''
+                    How often this btrbk instance is started. See systemd.time(7) for more information about the format.
+                    Setting it to null disables the timer, thus this instance can only be started manually.
+                  '';
+                };
+                settings = mkOption {
+                  type = let t = types.attrsOf (types.either types.str (t // { description = "instances of this type recursively"; })); in t;
+                  default = { };
+                  example = {
+                    snapshot_preserve_min = "2d";
+                    snapshot_preserve = "14d";
+                    volume = {
+                      "/mnt/btr_pool" = {
+                        target = "/mnt/btr_backup/mylaptop";
+                        subvolume = {
+                          "rootfs" = { };
+                          "home" = { snapshot_create = "always"; };
+                        };
+                      };
+                    };
+                  };
+                  description = lib.mdDoc "configuration options for btrbk. Nested attrsets translate to subsections.";
+                };
+              };
+            }
+          );
+        default = { };
+      };
+      sshAccess = mkOption {
+        description = lib.mdDoc "SSH keys that should be able to make or push snapshots on this system remotely with btrbk";
+        type = with types; listOf (
+          submodule {
+            options = {
+              key = mkOption {
+                type = str;
+                description = lib.mdDoc "SSH public key allowed to login as user `btrbk` to run remote backups.";
+              };
+              roles = mkOption {
+                type = listOf (enum [ "info" "source" "target" "delete" "snapshot" "send" "receive" ]);
+                example = [ "source" "info" "send" ];
+                description = lib.mdDoc "What actions can be performed with this SSH key. See ssh_filter_btrbk(1) for details";
+              };
+            };
+          }
+        );
+        default = [ ];
+      };
+    };
+
+  };
+  config = mkIf (sshEnabled || serviceEnabled) {
+    environment.systemPackages = [ pkgs.btrbk ] ++ cfg.extraPackages;
+    security.sudo = mkIf (sudo_doas == "sudo") {
+      extraRules = [
+        {
+            users = [ "btrbk" ];
+            commands = [
+            { command = "${pkgs.btrfs-progs}/bin/btrfs"; options = [ "NOPASSWD" ]; }
+            { command = "${pkgs.coreutils}/bin/mkdir"; options = [ "NOPASSWD" ]; }
+            { command = "${pkgs.coreutils}/bin/readlink"; options = [ "NOPASSWD" ]; }
+            # for ssh, they are not the same than the one hard coded in ${pkgs.btrbk}
+            { command = "/run/current-system/sw/bin/btrfs"; options = [ "NOPASSWD" ]; }
+            { command = "/run/current-system/sw/bin/mkdir"; options = [ "NOPASSWD" ]; }
+            { command = "/run/current-system/sw/bin/readlink"; options = [ "NOPASSWD" ]; }
+            ];
+        }
+      ];
+    };
+    security.doas = mkIf (sudo_doas == "doas") {
+      extraRules = let
+        doasCmdNoPass = cmd: { users = [ "btrbk" ]; cmd = cmd; noPass = true; };
+      in
+        [
+            (doasCmdNoPass "${pkgs.btrfs-progs}/bin/btrfs")
+            (doasCmdNoPass "${pkgs.coreutils}/bin/mkdir")
+            (doasCmdNoPass "${pkgs.coreutils}/bin/readlink")
+            # for ssh, they are not the same than the one hard coded in ${pkgs.btrbk}
+            (doasCmdNoPass "/run/current-system/sw/bin/btrfs")
+            (doasCmdNoPass "/run/current-system/sw/bin/mkdir")
+            (doasCmdNoPass "/run/current-system/sw/bin/readlink")
+
+            # doas matches command, not binary
+            (doasCmdNoPass "btrfs")
+            (doasCmdNoPass "mkdir")
+            (doasCmdNoPass "readlink")
+        ];
+    };
+    users.users.btrbk = {
+      isSystemUser = true;
+      # ssh needs a home directory
+      home = "/var/lib/btrbk";
+      createHome = true;
+      shell = "${pkgs.bash}/bin/bash";
+      group = "btrbk";
+      openssh.authorizedKeys.keys = map
+        (
+          v:
+          let
+            options = concatMapStringsSep " " (x: "--" + x) v.roles;
+            ioniceClass = {
+              "idle" = 3;
+              "best-effort" = 2;
+              "realtime" = 1;
+            }.${cfg.ioSchedulingClass};
+            sudo_doas_flag = "--${sudo_doas}";
+          in
+          ''command="${pkgs.util-linux}/bin/ionice -t -c ${toString ioniceClass} ${optionalString (cfg.niceness >= 1) "${pkgs.coreutils}/bin/nice -n ${toString cfg.niceness}"} ${pkgs.btrbk}/share/btrbk/scripts/ssh_filter_btrbk.sh ${sudo_doas_flag} ${options}" ${v.key}''
+        )
+        cfg.sshAccess;
+    };
+    users.groups.btrbk = { };
+    systemd.tmpfiles.rules = [
+      "d /var/lib/btrbk 0750 btrbk btrbk"
+      "d /var/lib/btrbk/.ssh 0700 btrbk btrbk"
+      "f /var/lib/btrbk/.ssh/config 0700 btrbk btrbk - StrictHostKeyChecking=accept-new"
+    ];
+    environment.etc = mapAttrs'
+      (
+        name: instance: {
+          name = "btrbk/${name}.conf";
+          value.source = mkConfigFile name instance.settings;
+        }
+      )
+      cfg.instances;
+    systemd.services = mapAttrs'
+      (
+        name: _: {
+          name = "btrbk-${name}";
+          value = {
+            description = "Takes BTRFS snapshots and maintains retention policies.";
+            unitConfig.Documentation = "man:btrbk(1)";
+            path = [ "/run/wrappers" ] ++ cfg.extraPackages;
+            serviceConfig = {
+              User = "btrbk";
+              Group = "btrbk";
+              Type = "oneshot";
+              ExecStart = "${pkgs.btrbk}/bin/btrbk -c /etc/btrbk/${name}.conf run";
+              Nice = cfg.niceness;
+              IOSchedulingClass = cfg.ioSchedulingClass;
+              StateDirectory = "btrbk";
+            };
+          };
+        }
+      )
+      cfg.instances;
+
+    systemd.timers = mapAttrs'
+      (
+        name: instance: {
+          name = "btrbk-${name}";
+          value = {
+            description = "Timer to take BTRFS snapshots and maintain retention policies.";
+            wantedBy = [ "timers.target" ];
+            timerConfig = {
+              OnCalendar = instance.onCalendar;
+              AccuracySec = "10min";
+              Persistent = true;
+            };
+          };
+        }
+      )
+      (filterAttrs (name: instance: instance.onCalendar != null)
+        cfg.instances);
+  };
+
+}
diff --git a/firestar/btrbk.nix b/firestar/btrbk.nix
index c2df045..3a02686 100644
--- a/firestar/btrbk.nix
+++ b/firestar/btrbk.nix
@@ -12,7 +12,7 @@ let
   });
 in
 {
-  services.btrbk = {
+  services.btrbk-patched = {
     sshAccess = [
       {
         key = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHTqU3EvTgY5/e9m6YyQWypQPK58t9iPmPnPYAvnODGB asonix@lionheart";
diff --git a/flake.nix b/flake.nix
index 69ede97..ac82ea9 100644
--- a/flake.nix
+++ b/flake.nix
@@ -8,39 +8,41 @@
       system = "x86_64-linux";
       specialArgs = attrs;
       modules = [
+        ./btrbk-patched/default.nix
         ./desktop.nix
-	./firestar
-	./fonts.nix
-	./packages.nix
-        (import ./user.nix {
-	  name = "Aode";
-	  authorizedKeys = [
-	    "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILojJubDCB2Mc4fw2mdp5Lzg5mTifXwawIVuyb3vr4lB asonix@graystripe"
-	  ];
-	})
-	{
-	  services.openssh = {
-	    enable = true;
-	    settings.PermitRootLogin = "no";
-	  };
-	}
+        ./firestar
+        ./fonts.nix
+        ./packages.nix
+          (import ./user.nix {
+          name = "Aode";
+          authorizedKeys = [
+            "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILojJubDCB2Mc4fw2mdp5Lzg5mTifXwawIVuyb3vr4lB asonix@graystripe"
+          ];
+        })
+        {
+          services.openssh = {
+            enable = true;
+            settings.PermitRootLogin = "no";
+          };
+        }
       ];
     };
     nixosConfigurations.graystripe = nixpkgs.lib.nixosSystem {
       system = "x86_64-linux";
       specialArgs = attrs;
       modules = [
+        ./btrbk-patched/default.nix
         ./desktop.nix
         ./fonts.nix
         ./graystripe
         ./packages.nix
         (import ./user.nix { name = "Tavi"; })
-	{
-	  services.openssh = {
-	    enable = true;
-	    settings.PermitRootLogin = "no";
-	  };
-	}
+        {
+          services.openssh = {
+            enable = true;
+            settings.PermitRootLogin = "no";
+          };
+        }
       ];
     };
   };
diff --git a/graystripe/btrbk.nix b/graystripe/btrbk.nix
index 4cf811b..3fa01f6 100644
--- a/graystripe/btrbk.nix
+++ b/graystripe/btrbk.nix
@@ -12,7 +12,7 @@ let
   });
 in
 {
-  services.btrbk = {
+  services.btrbk-patched = {
     sshAccess = [
       {
         key = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHTqU3EvTgY5/e9m6YyQWypQPK58t9iPmPnPYAvnODGB asonix@lionheart";