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Revision as of 23:48, 3 June 2024

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Add short command to know the difference between different disk/by-* paths
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imported>Ragnis
m (Fix typo)
(Add short command to know the difference between different disk/by-* paths)
 
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[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]].
[https://zfsonlinux.org/ {{PAGENAME}}] ([[wikipedia:en:{{PAGENAME}}]]) - also known as [https://openzfs.org/ OpenZFS] ([[wikipedia:en:OpenZFS]]) - is a modern filesystem[[category:filesystem]] which is well supported on [[NixOS]].


There are a lot of packages for [[{{PAGENAME}}]]. For example there is the ''zfs'' package (''ZFS Filesystem Linux Kernel module'') itself.<ref>https://search.nixos.org/packages?channel=unstable&show=zfs&query=zfs</ref> But there are also a lot of packages of the [[{{PAGENAME}}]] ecosystem available.
There are a lot of packages for [[{{PAGENAME}}]]. For example there is the ''zfs'' package (''ZFS Filesystem Linux Kernel module'') itself.<ref>https://search.nixos.org/packages?channel=unstable&show=zfs&query=zfs</ref> But there are also a lot of packages of the [[{{PAGENAME}}]] ecosystem available.
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Newest kernels might not be supported by ZFS yet. If you are running an newer kernel which is not yet officially supported by zfs, the zfs module will refuse to evaluate and show up as ''broken''.  Use <code>boot.kernelPackages = config.boot.zfs.package.latestCompatibleLinuxPackages;</code> to use the latest compatible kernel.
Newest kernels might not be supported by ZFS yet. If you are running an newer kernel which is not yet officially supported by zfs, the zfs module will refuse to evaluate and show up as ''broken''.  Use <code>boot.kernelPackages = config.boot.zfs.package.latestCompatibleLinuxPackages;</code> to use the latest compatible kernel.


==== missing support for SWAP on ZFS ====
==== partial support for SWAP on ZFS ====


ZFS does not support swapfiles. Hibernation must be either disabled with <code><nowiki>boot.kernelParams = [ "nohibernate" ];</nowiki></code>, or be enabled with a separate, non-ZFS swap partition.
ZFS does not support swapfiles. SWAP devices must be used instead. Additionally, hibernation is disabled by default due to a [https://github.com/NixOS/nixpkgs/pull/208037 high risk] of data corruption. Note that even if / after that pull request is merged, it does not fully mitigate the risk. If you wish to enable hibernation regardless, set <code>boot.zfs.allowHibernation = true</code>.


==== boot.zfs.devNodes in virtual machines ====
==== boot.zfs.devNodes ====


If you are running within a VM and NixOS fails to import the zpool on reboot, you may need to add <syntaxhighlight lang="nix" inline>boot.zfs.devNodes = "/dev/disk/by-path";</syntaxhighlight> or <syntaxhighlight lang="nix" inline>boot.zfs.devNodes = "/dev/disk/by-partuuid";</syntaxhighlight> to your configuration.nix file.  
If NixOS fails to import the zpool on reboot, you may need to add <syntaxhighlight lang="nix" inline>boot.zfs.devNodes = "/dev/disk/by-path";</syntaxhighlight> or <syntaxhighlight lang="nix" inline>boot.zfs.devNodes = "/dev/disk/by-partuuid";</syntaxhighlight> to your configuration.nix file.
 
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.


==== declarative mounting of ZFS datasets ====
==== declarative mounting of ZFS datasets ====
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Under manual partitioning [https://nixos.org/manual/nixos/stable/#sec-installation-manual-partitioning] do this instead:
Under manual partitioning [https://nixos.org/manual/nixos/stable/#sec-installation-manual-partitioning] do this instead:


'''Partition your disk with an boot and an zfs partition with your favorite partition tool.'''
'''Partition your disk with your favorite partition tool.'''
 
We need the following partitions:
 
* 1G for boot partition with "boot" as the partition label (also called name in some tools) and ef00 as partition code
* 10G for a swap partition with "swap" as the partition label and 8200 as partition code. We will encrypt this with a random secret on each boot.
* The rest of disk space for zfs with "root" as the partition label and 8300 as partition code (default code)


Eg. 1G for boot partion, rest for zfs.
Reason for swap partition: ZFS does use a caching mechanism that is different from the normal Linux cache infrastructure.
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.


Example output from fdisk:
Example output from fdisk:


<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
sudo gdisk /dev/nvme0n1
GPT fdisk (gdisk) version 1.0.9.1
...
Command (? for help): p
Disk /dev/nvme0n1: 500118192 sectors, 238.5 GiB
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): CA926E8C-47F6-416A-AD1A-C2190CF5D1F8
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 500118158
Partitions will be aligned on 2048-sector boundaries
Total free space is 2669 sectors (1.3 MiB)


fdisk /dev/nvme0n1
Number  Start (sector)    End (sector) Size      Code  Name
Command (m for help): p
  1            2048        2099199  1024.0 MiB  EF00  boot
  2        2099200        23070719  10.0 GiB    8200  swap
  3        23070720      500117503  227.5 GiB  8300  root


Disk /dev/nvme0n1: 931.51 GiB, 1000204886016 bytes, 1953525168 sectors
Command (? for help):  
...
Device          Start        End    Sectors  Size Type
/dev/nvme0n1p1    2048    2099199    2097152    1G EFI System
/dev/nvme0n1p2 2099200 1953523711 1951424512 930.5G Linux filesystem
</syntaxhighlight>
</syntaxhighlight>
'''Note:''' Remember to set boot partition (first partition) to "EFI System" type


'''Make zfs pool with encryption and mount points:'''
'''Make zfs pool with encryption and mount points:'''
'''Note:''' zpool config can significantly affect performance (especially the ashift option) so you may want to do some research. The [https://jrs-s.net/2018/08/17/zfs-tuning-cheat-sheet/ ZFS tuning cheatsheet] or [https://wiki.archlinux.org/title/ZFS#Storage_pools ArchWiki] is a good place to start.
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
zpool create -O encryption=on -O keyformat=passphrase -O keylocation=prompt -O compression=on -O mountpoint=none -O xattr=sa -O acltype=posixacl zpool /dev/nvme0n1p2
zpool create -O encryption=on -O keyformat=passphrase -O keylocation=prompt -O compression=zstd -O mountpoint=none -O xattr=sa -O acltype=posixacl -o ashift=12 zpool /dev/nvme0n1p2


zfs create -o mountpoint=legacy zpool/root
zfs create zpool/root
zfs create -o mountpoint=legacy zpool/nix
zfs create zpool/nix
zfs create -o mountpoint=legacy zpool/var
zfs create zpool/var
zfs create -o mountpoint=legacy zpool/home
zfs create zpool/home


mkdir /mnt/root
mkdir -p /mnt
mount -t zfs zpool/root /mnt
mount -t zfs zpool/root /mnt -o zfsutil
mkdir /mnt/nix /mnt/var /mnt/home
mkdir /mnt/nix /mnt/var /mnt/home


mount -t zfs zpool/nix /mnt/nix
mount -t zfs zpool/nix /mnt/nix -o zfsutil
mount -t zfs zpool/var /mnt/var
mount -t zfs zpool/var /mnt/var -o zfsutil
mount -t zfs zpool/home /mnt/home
mount -t zfs zpool/home /mnt/home -o zfsutil
</syntaxhighlight>
</syntaxhighlight>


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mkfs.fat -F 32 -n boot /dev/nvme0n1p1
mkfs.fat -F 32 -n boot /dev/nvme0n1p1
</syntaxhighlight>
</syntaxhighlight>


'''Installation:'''
'''Installation:'''
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<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
mkdir -p /mnt/boot
mkdir -p /mnt/boot
mount /dev/disk/by-label/boot /mnt/boot
mount /dev/disk/by-partlabel/boot /mnt/boot
</syntaxhighlight>
</syntaxhighlight>


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<syntaxhighlight lang="nix">
<syntaxhighlight lang="nix">
Boot loader config for configuration.nix:
{
   boot.loader.grub = {
  # Boot loader config for configuration.nix:
    enable = true;
   boot.loader.systemd-boot.enable = true;
    zfsSupport = true;
 
    efiSupport = true;
  # for local disks that are not shared over the network, we don't need this to be random
     efiInstallAsRemovable = true;
  networking.hostId = "8425e349";
     mirroredBoots = [
 
      { devices = [ "nodev"]; path = "/boot"; }
  fileSystems."/" = {
     ];
     device = "zpool/root";
     fsType = "zfs";
    # the zfsutil option is needed when mounting zfs datasets without "legacy" mountpoints
     options = [ "zfsutil" ];
   };
   };


   fileSystems."/" =
   fileSystems."/nix" = {
     { device = "zpool/root";
     device = "zpool/nix";
      fsType = "zfs";
    fsType = "zfs";
     };
     options = [ "zfsutil" ];
  };


   fileSystems."/nix" =
   fileSystems."/var" = {
     { device = "zpool/nix";
     device = "zpool/var";
      fsType = "zfs";
    fsType = "zfs";
     };
     options = [ "zfsutil" ];
  };


   fileSystems."/var" =
   fileSystems."/home" = {
     { device = "zpool/var";
     device = "zpool/home";
      fsType = "zfs";
    fsType = "zfs";
     };
     options = [ "zfsutil" ];
  };


   fileSystems."/home" =
   fileSystems."/boot" = {
    { device = "zpool/home";
  device = "/dev/disk/by-partlabel/boot";
      fsType = "zfs";
  fsType = "vfat";
    };
  };


   fileSystems."/boot" =
   swapDevices = [{
     { device = "/dev/disk/by-uuid/2A11-F4EF";
     device = "/dev/disk/by-partlabel/swap";
      fsType = "vfat";
    randomEncryption = true;
    };
  }];
 
}
  swapDevices = [ ];
</syntaxhighlight>
</syntaxhighlight>
'''Note:''' Remove / comment out <syntaxhighlight lang="nix" inline>boot.loader.systemd-boot.enable = true;</syntaxhighlight> config if added by<syntaxhighlight lang="nix" inline>nixos-generate-config</syntaxhighlight>


== Importing on boot ==
== Importing on boot ==
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};
};
</syntaxhighlight>
</syntaxhighlight>
=== Zpool created with bus-based disk names ===
If you used bus-based disk names in the <syntaxhighlight inline>zpool create</syntaxhighlight> command, e.g., <syntaxhighlight inline>/dev/sda</syntaxhighlight>, NixOS may run into issues importing the pool if the names change. Even if the pool is able to be mounted (with <syntaxhighlight lang="nix" inline>boot.zfs.devNodes = "/dev/disk/by-partuuid";</syntaxhighlight> set), this may manifest as a <syntaxhighlight inline>FAULTED</syntaxhighlight> disk and a <syntaxhighlight inline>DEGRADED</syntaxhighlight> pool reported by <syntaxhighlight inline>zpool status</syntaxhighlight>. The fix is to re-import the pool using disk IDs:
<syntaxhighlight>
# zpool export zpool_name
# zpool import -d /dev/disk/by-id zpool_name
</syntaxhighlight>
The import setting is reflected in <syntaxhighlight inline="" lang="bash">/etc/zfs/zpool.cache</syntaxhighlight>, so it should persist through subsequent boots.
=== Zpool created with disk IDs ===
If you used disk IDs to refer to disks in the <code>zpool create</code> command, e.g., <code>/dev/disk/by-id</code>, then NixOS may consistently fail to import the pool unless <code>boot.zfs.devNodes = "/dev/disk/by-id"</code> is also set.


== Mount datasets at boot ==
== Mount datasets at boot ==
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     # Add the load-key command to the .profile
     # Add the load-key command to the .profile
     echo "zfs load-key -a; killall zfs" >> /root/.profile
     echo "zfs load-key -a; killall zfs" >> /root/.profile
     };
     '';
   };
   };
};
};
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