74 lines
2.1 KiB
Nix
74 lines
2.1 KiB
Nix
{ lib, config, ... }:
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let
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cfg = config.ephemeral;
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in
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{
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options.ephemeral = {
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enable = lib.mkEnableOption "ephemeral root with automatic rollback";
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rootDevice = lib.mkOption {
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type = lib.types.str;
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example = "/dev/mapper/cryptroot";
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description = "Device path for the root btrfs filesystem";
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};
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rootSubvolume = lib.mkOption {
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type = lib.types.str;
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example = "@root";
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description = "Name of the root btrfs subvolume";
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};
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oldRootRetentionDays = lib.mkOption {
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type = lib.types.int;
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default = 30;
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description = "Number of days to keep old root snapshots before deletion";
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};
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};
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config = lib.mkIf cfg.enable {
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boot.initrd.systemd.services.recreate-root = {
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description = "Rolling over and creating new filesystem root";
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requires = [ "initrd-root-device.target" ];
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after = [
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"local-fs-pre.target"
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"initrd-root-device.target"
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];
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requiredBy = [ "initrd-root-fs.target" ];
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before = [ "sysroot.mount" ];
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unitConfig = {
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AssertPathExists = "/etc/initrd-release";
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DefaultDependencies = false;
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};
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serviceConfig = {
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Type = "oneshot";
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RemainAfterExit = true;
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};
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script = ''
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mkdir /btrfs_tmp
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mount ${cfg.rootDevice} /btrfs_tmp
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if [[ -e /btrfs_tmp/${cfg.rootSubvolume} ]]; then
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mkdir -p /btrfs_tmp/old_roots
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timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp/${cfg.rootSubvolume})" "+%Y-%m-%-d_%H:%M:%S")
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mv /btrfs_tmp/${cfg.rootSubvolume} "/btrfs_tmp/old_roots/$timestamp"
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fi
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delete_subvolume_recursively() {
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IFS=$'\n'
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for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
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delete_subvolume_recursively "/btrfs_tmp/$i"
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done
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btrfs subvolume delete "$1"
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}
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for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +${toString cfg.oldRootRetentionDays}); do
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delete_subvolume_recursively "$i"
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done
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btrfs subvolume create /btrfs_tmp/${cfg.rootSubvolume}
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umount /btrfs_tmp
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'';
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};
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};
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}
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