Hello, I use disko for all my machines running preservation with tmpfs and btrfs. I've been reoing my homelab and decided to try out bcachefs but currently my system just boots to emergency mode. As I said I'm new to bcachefs, so if I am doing anything obviously wrong that anyone can point out that would be greatly appreciated. Running the same configurations for preservation that I daily drive on my machine so I dont think its anything there. Not sure if I'm just doing subvolumes incorrectly or something like that.

{
  disko.devices = {
    disk = {
      nix = {
        type = "disk";
        device = "/dev/disk/by-id/nvme-WD_BLACK_SN770_1TB_234252800502";
        content = {
          type = "gpt";
          partitions = {
            boot = {
              size = "1G";
              type = "EF00";
              content = {
                type = "filesystem";
                format = "vfat";
                mountpoint = "/boot";
                mountOptions = ["umask=0077"];
              };
            };

            root = {
              size = "100%";
              content = {
                type = "bcachefs";
                filesystem = "root";
                label = "root";
                extraFormatArgs = ["--discard"];
              };
            };
          };
        };
      };

      # NVME raid drives
      nvme-6749 = {
        type = "disk";
        device = "/dev/disk/by-id/nvme-CT2000P310SSD8_24514CF66749";
        content = {
          type = "bcachefs";
          filesystem = "np1";
          label = "np1.6749";
          extraFormatArgs = ["--discard"];
        };
      };

      nvme-7818 = {
        type = "disk";
        device = "/dev/disk/by-id/nvme-CT2000P310SSD8_24514CF67818";
        content = {
          type = "bcachefs";
          filesystem = "np1";
          label = "np1.7818";
          extraFormatArgs = ["--discard"];
        };
      };

      nvme-7847 = {
        type = "disk";
        device = "/dev/disk/by-id/nvme-CT2000P310SSD8_24514CF67847";
        content = {
          type = "bcachefs";
          filesystem = "np1";
          label = "np1.7847";
          extraFormatArgs = ["--discard"];
        };
      };

      nvme-7917 = {
        type = "disk";
        device = "/dev/disk/by-id/nvme-CT2000P310SSD8_24514CF67917";
        content = {
          type = "bcachefs";
          filesystem = "np1";
          label = "np1.7917";
          extraFormatArgs = ["--discard"];
        };
      };

      # HDD raid drives
      hdd-3ALH = {
        type = "disk";
        device = "/dev/disk/by-id/ata-ST4000VN006-3CW104_ZW603ALH";
        content = {
          type = "bcachefs";
          filesystem = "dp1";
          label = "dp1.3ALH";
          extraFormatArgs = ["--discard"];
        };
      };

      hdd-40NG = {
        type = "disk";
        device = "/dev/disk/by-id/ata-ST4000VN006-3CW104_ZW6040NG";
        content = {
          type = "bcachefs";
          filesystem = "dp1";
          label = "dp1.40NG";
          extraFormatArgs = ["--discard"];
        };
      };
    };

    bcachefs_filesystems = {
      root = {
        type = "bcachefs_filesystem";
        extraFormatArgs = [
          "--compression zstd:1"
        ];
        subvolumes = {
          nix = {
            mountpoint = "/nix";
          };
          root = {
            mountpoint = "/nix/persist";
          };
          home = {
            mountpoint = "/nix/persist/home";
          };
        };
      };

      np1 = {
        type = "bcachefs_filesystem";
        extraFormatArgs = [
          "--compression zstd:1"
          "--erasure_code"
          "--data_replicas 1"
          "--metadata_replicas 2"
        ];
        subvolumes = {
          root = {
            mountpoint = "/nix/persist/npool";
          };
        };
      };

      dp1 = {
        type = "bcachefs_filesystem";
        extraFormatArgs = [
          "--compression zstd:10"
          "--replicas 2"
        ];
        subvolumes = {
          root = {
            mountpoint = "/nix/persist/dpool";
          };
        };
      };
    };

    nodev."/" = {
      fsType = "tmpfs";
      mountOptions = [
        "defaults"
        "size=6G"
        "mode=755"
      ];
    };
  };
}

In reply to @zimward:zimward.moe
bcachefs didn't like to format my drive (its an relatively old nvme), that was about 6months ago. can you verify that the partition/drives have been formatted?

This is my config:

{ inputs, ... }:
let
  ssdDevice = "/dev/disk/by-id/nvme-SAMSUNG_MZVLB256HAHQ-000H1_S425NX2M363531";
  hddDevice = "/dev/disk/by-id/ata-ST2000DM008-2UB102_ZK20P7NY";
  wdDevice = "/dev/disk/by-id/ata-WDC_WD10EARS-00Y5B1_WD-WCAV5S128768";
in
{
  imports = [
    inputs.disko.nixosModules.disko
  ];

  boot.supportedFilesystems = [ "bcachefs" ];

  disko.devices = {
    disk = {
      # NVMe SSD - Fast tier for metadata and caching
      nvme = {
        type = "disk";
        device = ssdDevice;
        content = {
          type = "gpt";
          partitions = {
            ESP = {
              priority = 1;
              name = "ESP";
              size = "512M";
              type = "EF00";
              content = {
                type = "filesystem";
                format = "vfat";
                mountpoint = "/boot";
                mountOptions = [ "umask=0077" ];
              };
            };
            # NVMe partition for bcachefs (fast tier)
            main = {
              size = "100%";
              content = {
                type = "bcachefs";
                filesystem = "main_bcachefs";
                label = "ssd.nvme";
                extraFormatArgs = [ "--discard" ];
              };
            };
          };
        };
      };

      # HDD - Bulk storage tier
      hdd = {
        type = "disk";
        device = hddDevice;
        content = {
          type = "gpt";
          partitions = {
            # HDD partition for bcachefs (storage tier)
            main = {
              size = "100%";
              content = {
                type = "bcachefs";
                filesystem = "main_bcachefs";
                label = "hdd.storage";
              };
            };
          };
        };
      };

      # Western Digital HDD - Separate btrfs filesystem
      WD10EARS = {
        type = "disk";
        device = wdDevice;
        content = {
          type = "gpt";
          partitions = {
            main = {
              size = "100%";
              content = {
                type = "btrfs";
                extraArgs = [ "-f" ];
                subvolumes = {
                  "@" = {
                    mountpoint = "/mnt/wd10ears";
                    mountOptions = [
                      "compress=zstd"
                      "noatime"
                    ];
                  };
                };
              };
            };
          };
        };
      };
    };

    bcachefs_filesystems = {
      main_bcachefs = {
        type = "bcachefs_filesystem";
        extraFormatArgs = [
          "--compression=lz4"
          "--background_compression=zstd:6"
          # Tiering configuration
          "--background_target=hdd"
          "--foreground_target=ssd"
          "--promote_target=ssd"
          "--metadata_target=ssd"
        ];
        subvolumes = {
          # Root filesystem - equivalent to @root
          "@root" = {
            mountpoint = "/";
            mountOptions = [
              "noatime"
            ];
          };

          # Nix store - equivalent to @nix
          "@nix" = {
            mountpoint = "/nix";
            mountOptions = [
              "noatime"
            ];
          };

          # Backups directory
          "@backups" = {
            mountpoint = "/var/backups";
            mountOptions = [
              "noatime"
            ];
          };
        };
      };
    };
  };

}

I've been having the same issue, I cant get my system to boot with root on bcachefs using disko. The filesystem exists, I can mount create and view files but the system just doesnt boot. I can boot off another fs and have disko create and mount drives other than root. Was trying to debug more before I posted anything.

Been feeling a little crazy cause I couldn't find any mention of the issue, almost glad to see its not just me