Adding a second drive to a disko config

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1

I am using disko in combination with nixos-anywhere to install a VM on proxmox.
That has worked out nicely so far. Below is my config for that for reference, it is basically an exact copy of the disko example flake.

      disko.devices = {
        disk.disk1 = {
          device = "/dev/vda";
          type = "disk";
          content = {
            type = "gpt";
            partitions = {
              boot = {
                name = "boot";
                size = "1M";
                type = "EF02";
              };
              esp = {
                name = "ESP";
                size = "500M";
                type = "EF00";
                content = {
                  type = "filesystem";
                  format = "vfat";
                  mountpoint = "/boot";
                };
              };
              root = {
                name = "root";
                size = "100%";
                content = {
                  type = "lvm_pv";
                  vg = "pool";
                };
              };
            };
          };
        };
        lvm_vg = {
          pool = {
            type = "lvm_vg";
            lvs = {
              root = {
                size = "100%FREE";
                content = {
                  type = "filesystem";
                  format = "ext4";
                  mountpoint = "/";
                  mountOptions = [ "defaults" ];
                };
              };
            };
          };
        };
      };

I would now like to add a second drive to that VM.
I have already added an empty 1TB Drive through the proxmox webui on device virtio12 and I can see it as /dev/vdm when running lsblk.
I have added the following disko config for it:

      disko.devices.disk.disk2 = {
        device = "/dev/vdm";
        type = "disk";
        content = {
          type = "gpt";
          partitions = {
            main = {
              start = "1MiB";
              size = "100%";
              content = {
                type = "filesystem";
                format = "ext4";
                mountpoint = "/storage";
              };
            };
          };
        };
      };

When I apply that new configuration to my VM, it fails with Failed to start local-fs.target and the system does not finish booting anymore and enters emergency mode after A start job is running for /dev/disk/by-partlabel/disk-disk2-main times out.

Do I simply have an error in my partition setup, or do I have to create the mountpoint manually first? Or does disko not support formatting and mounting new disks on existing systems?

2

What errors does local-fs.target have in its log? Also, I believe that Disko in a flake will try to mount disks, but not create them; have you run the Disko format,mount commands or created the EXT4 partition yourself?

3

Unfortunately I am unable to interact with the VM’s terminal once systemd enters emergency mode, but I will try more.

While I am using flakes, I also load the disko module into my nixos config.
Maybe it is time for me to read the code of that module.

4

Turns out it is currently not possible to update an existing disko setup.
This issue tracks that feature request:

I still want it to work when I recreate the VM for whatever reason, so I formatted the disk manually and created a file system on it. I gave the partition the same label from the systemd error, which worked.
(the default label name is defined here disko/lib/types/gpt.nix at a4cb7bf73f264d40560ba527f9280469f1f081c6 · nix-community/disko · GitHub)

5

You might be interested in disko-zfs that can execute updates: Disko-zfs: manage your datasets declaratively

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6

disko-zfs only handles ZFS and nothing else. Switching to ZFS might be a bit too much just to get declarative updates…

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