How to auto mount / permanently mount external devices on NixOS

Question

I have a USB stick and an NTFS hard drive partition that I'd want to use in NixOS. On some other distribution, I'd mount it using ntfs-3g in /mnt. But on NixOS, the directory doesn't exist; I suppose NixOS has some other canonical way and/or place of doing that.

In NixOS, how should one set up automounting of external partitions, preferably using configuration.nix?

Answer 1

Well, I costumarily use bashmount or udisksctl to mount USB sticks. They will be mounted in /run/media/$(user name)/$(drive label or UUID).

But if you are talking about an internal harddisk or partition in a local harddrive, the simplest way is:

1. Create a directory of your preference, as /mnt/windows-partition
2. Mount the desired partition, say /dev/sdn5, in that directory:

$ mount /dev/sdn5 /mnt/windows-partition

3. Run nixos-generate-config. It will update /etc/nixos/hardware-configuration.nix to match the new partition configuration (and configuration.nix stays untouched, unless you use the --force option).
4. And, finally, a nixos-rebuild switch!

Answer 2

I personally use udisks for that. That means, if i want to mount an USB stick, i just have to plug it in and run:

$ udisksctl mount -b /dev/sdc

I aliased udisksctl mount -b to udm to make it even shorter. The device is then mounted in /run/media/$USER/$DEVICE_LABEL and accessible for you.

I think, some tools (e.g. nautilus and ldm) can do that automatically for you.

EDIT: ah, i just found out that udisks can also automount devices.

Answer 3

Directly modifying hardware-configuration.nix file

---

To achieve the same results as mentioned in other answers, you can as well add another fileSystems config entry in hardware-configuration.nix:

{
  ...

  fileSystems."${mount_location}" = {
    device = "/dev/${device}";
    fsType = "${filesystem_extension}";
  };

  ...
}

NOTES:

To get filesystem extension information about a particular partition run:

df -T | grep /dev/${device}

Example configuration for /dev/sda1 device, having ext4 file system extension, that is to be mounted at /mnt/sda1 location:

{
  ...

  fileSystems."/mnt/sda1" = {
    device = "/dev/sda1";
    fsType = "ext4";
  };

  ...
}

I think that such a solution is more unique, as the device name would not be overwritten by NixOS specific namespaces as in nixos-generate-config's solution.