ZFS: Difference between revisions

[https://zfsonlinux.org/ {{PAGENAME}}] ([[wikipedia:en:{{PAGENAME}}]]), also known as [https://openzfs.org/ OpenZFS] ([[wikipedia:en:OpenZFS]]), is a modern filesystem which is well supported on [[NixOS]].

[[category:filesystem]]

== Limitations ==

ZFS often does not support the latest Kernel versions. It is recommended to use an LTS Kernel version whenever possible; the NixOS default Kernel is generally suitable. See [[Linux kernel|Linux Kernel]] for more information about configuring a specific Kernel version.

===== Selecting the latest ZFS-compatible Kernel =====

<syntaxhighlight lang="nix">

{

   lib,

   pkgs,

   ...

}:

let

   zfsCompatibleKernelPackages = lib.filterAttrs (

     name: kernelPackages:

     (builtins.match "linux_[0-9]+_[0-9]+" name) != null

     && (builtins.tryEval kernelPackages).success

   ) pkgs.linuxKernel.packages;

   latestKernelPackage = lib.last (

===== Using unstable, pre-release ZFS =====

==== Partial support for swap on ZFS ====

The differences can be tested by running <code>zpool import -d /dev/disk/by-id</code> when none of the pools are discovered, eg. a live iso.

== Guides ==

{{warning|This guide is not endorsed by NixOS and some features like immutable root do not have upstream support and could break on updates. If an issue arises while following this guide, please consult the guides support channels.}}

* Giving understandable, easy to follow instructions which are close to the standard installation guide

* Integrating ZFS into your existing config

Start from here in the NixOS manual: [https://nixos.org/manual/nixos/stable/#sec-installation-manual].

Under manual partitioning [https://nixos.org/manual/nixos/stable/#sec-installation-manual-partitioning] do this instead:

We need the following partitions:

In low-memory situations, ZFS therefore might need a bit longer to free up memory from its cache. The swap partition will help with that.

<syntaxhighlight lang="bash">

The operation has completed successfully.

</syntaxhighlight>

<syntaxhighlight lang=bash>

Number  Start (sector)    End (sector)  Size      Code  Name

</syntaxhighlight>

<syntaxhighlight lang=bash>

BOOT=/dev/disk/by-id/nvme-SKHynix_HFS512GDE9X081N_FNB6N634510106K5O-part1

</syntaxhighlight>

<syntaxhighlight lang="bash">

zfs create zpool/home

mkdir -p /mnt

mount -t zfs zpool/root /mnt -o zfsutil

mkdir /mnt/nix /mnt/var /mnt/home

mount -t zfs zpool/nix /mnt/nix -o zfsutil

mount -t zfs zpool/var /mnt/var -o zfsutil

</syntaxhighlight>

<syntaxhighlight lang="bash">

mkfs.fat -F 32 -n boot $BOOT

</syntaxhighlight>

<syntaxhighlight lang="bash">

mkswap -L swap $SWAP

</syntaxhighlight>

# Mount boot

mkdir -p /mnt/boot

mount $BOOT /mnt/boot

Now edit the configuration.nix that was just created in <code>/mnt/etc/nixos/configuration.nix</code> and make sure to have at least the following content in it.

{

...

   # for local disks that are not shared over the network, we don't need this to be random

...

Now check the hardware-configuration.nix in <code>/mnt/etc/nixos/hardware-configuration.nix</code> and add whats missing e.g. <code>options = [ "zfsutil" ]</code> for all filesystems except boot and <code>randomEncryption = true;</code> for the swap partition. Also change the generated swap device to the partition we created e.g. <code>/dev/disk/by-id/nvme-SKHynix_HFS512GDE9X081N_FNB6N634510106K5O-part2</code> in this case and <code>/dev/disk/by-id/nvme-SKHynix_HFS512GDE9X081N_FNB6N634510106K5O-part1</code> for boot.

...

   fileSystems."/" = {  

     fsType = "zfs";

     # the zfsutil option is needed when mounting zfs datasets without "legacy" mountpoints

   };

     device = "zpool/nix";

     fsType = "zfs";

   };

     device = "zpool/var";

     fsType = "zfs";

   };

     device = "zpool/home";

     fsType = "zfs";

   };

   swapDevices = [{

   }];

}

Now you may install NixOS with <code>nixos-install</code>.

== Take snapshots automatically ==

== NFS share ==

Then, configure an alias for root account. With this alias configured, all mails sent to root, such as cron job results and failed sudo login events, will be redirected to the configured email account.

</syntaxhighlight>