NixOS Wiki

Impermanence: Difference between revisions

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m Replaced $USERNAME with <username> so that it's not confused with normal variables
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{{warning|When setting up impermanence, make sure that you have declared password for your user to be able to log-in after the deployment as for example the nixos installer declares passwords imperatively.}}
Impermanence in NixOS is where your root directory gets wiped every reboot (such as by mounting a tmpfs to /). Such a setup is possible because NixOS only needs <code>/boot</code> and <code>/nix</code> in order to boot, all other system files are simply links to files in <code>/nix</code>. <code>/boot</code> and <code>/nix</code> still need to be stored on a hard drive or SSD.
Impermanence in NixOS is where your root directory gets wiped every reboot (such as by mounting a tmpfs to /). Such a setup is possible because NixOS only needs <code>/boot</code> and <code>/nix</code> in order to boot, all other system files are simply links to files in <code>/nix</code>. <code>/boot</code> and <code>/nix</code> still need to be stored on a hard drive or SSD.


Example <code>hardwareconfiguration.nix</code> settings:
Example <code>hardware-configuration.nix</code> settings:
<syntaxhighlight lang="nix">
<syntaxhighlight lang="nix">
   fileSystems."/" =
   fileSystems."/" =
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Some files and folders should be persisted between reboots though (such as <code>/etc/nixos/</code>). This can be accomplished through bind mounts or by using the [https://github.com/nix-community/impermanence NixOS Impermanence module,] which will set up bind mounts and links as needed.
Some files and folders should be persisted between reboots though (such as <code>/etc/nixos/</code>). This can be accomplished through bind mounts or by using the [https://github.com/nix-community/impermanence NixOS Impermanence module,] which will set up bind mounts and links as needed.


Impermanence module:
 
Put in <code>configuration.nix</code>:
<syntaxhighlight lang="nix">
<syntaxhighlight lang="nix">
{ config, pkgs, ... }:
{ config, pkgs, ... }:
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   imports = [ "${impermanence}/nixos.nix" ];
   imports = [ "${impermanence}/nixos.nix" ];


  # this folder is where the files will be stored (don't put it in tmpfs)
   environment.persistence."/nix/persist/system" = {
   environment.persistence."/nix/persist/system" = {  
    hideMounts = true;
     directories = [
     directories = [
      "/etc/nixos"    # bind mounted from /nix/persist/system/etc/nixos to /etc/nixos
      "/etc/NetworkManager"
       "/var/log"
       "/var/log"
       "/var/lib"
       "/var/lib/bluetooth"
      "/var/lib/nixos"
      "/var/lib/systemd/coredump"
      "/var/lib/systemd/timers"
      "/etc/NetworkManager/system-connections"
      { directory = "/var/lib/colord"; user = "colord"; group = "colord"; mode = "u=rwx,g=rx,o="; }
     ];
     ];
     files = [
     files = [
#      "/etc/machine-id"
      "/etc/machine-id"
       "/etc/nix/id_rsa"
       { file = "/etc/nix/id_rsa"; parentDirectory = { mode = "u=rwx,g=,o="; }; }
     ];
     ];
   };
   };
}
}
</syntaxhighlight>
</syntaxhighlight>


=== Home Managing ===
=== Home Managing ===
You can just make a home partition on a drive and mount it as normal, so everything in <code>/home</code> or <code>/home/username</code> will be persisted. If you want your home to be impermanent as well, then mount it on tmpfs the same way as root.
You can just make a home partition on a drive and mount it as normal, so everything in <code>/home</code> or <code>/home/username</code> will be persisted. If you want your home to be impermanent as well, then mount it on tmpfs the same way as root.


For persisting files in your home, you could simply use [https://github.com/nix-community/home-manager Home Manager] like normal. However, then files are stored read-only in the Nix store. In order to persist files while still being writable, you can use the [https://github.com/nix-community/impermanence Home Manager Impermanence module]. It will fuse mount and link files as necessary.
For persisting files in your home, you could simply use [https://github.com/nix-community/home-manager Home Manager] like normal. However, then files are stored read-only in the Nix store. In order to persist files while still being writable, you can use the [https://github.com/nix-community/impermanence Home Manager Impermanence module]. It will fuse mount folders and link files from persistent storage into your home directory.




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Example:
Put in <code>configuration.nix</code>:
<syntaxhighlight lang="nix">
<syntaxhighlight lang="nix">
{ config, pkgs, ... }:
{ config, pkgs, ... }:
let
let
   home-manager = builtins.fetchTarball "https://github.com/nix-community/home-manager/archive/release-21.11.tar.gz";
   home-manager = builtins.fetchTarball "https://github.com/nix-community/home-manager/archive/release-22.05.tar.gz";
   impermanence = builtins.fetchTarball "https://github.com/nix-community/impermanence/archive/master.tar.gz";
   impermanence = builtins.fetchTarball "https://github.com/nix-community/impermanence/archive/master.tar.gz";
in
in
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   ];
   ];


  # might not be needed
   programs.fuse.userAllowOther = true;
   programs.fuse.userAllowOther = true;


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     programs = {
     programs = {
       home-manager.enable = true;
       home-manager.enable = true;
       git = {  # can use home-manager normally as well as with persistence
       git = {  # can use home-manager normally as well as with persistence
         enable = true;
         enable = true;
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         "Atom/.atom/atom-discord"   
         "Atom/.atom/atom-discord"   
         "Atom/.atom/packages"
         "Atom/.atom/packages"
        "Firefox/.mozilla"  # bind mounted from /nix/dotfiles to /home/$USERNAME/.mozilla
         "Clementine/.config/Clementine"
         "Clementine/.config/Clementine"
        # fuse mounted from /nix/dotfiles/Firefox/.mozilla to /home/$USERNAME/.mozilla
        "Firefox/.mozilla"
       ];
       ];
       files = [
       files = [
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       allowOther = true;
       allowOther = true;
       directories = [
       directories = [
         ".config/gtk-3.0"  # fuse mounted to /home/$USERNAME/.config/gtk-3.0
         ".config/gtk-3.0"  # fuse mounted from /nix/dotfiles/Plasma/.config/gtk-3.0
         ".config/gtk-4.0"
         ".config/gtk-4.0"     # to /home/$USERNAME/.config/gtk-3.0
         ".config/KDE"
         ".config/KDE"
         ".config/kde.org"
         ".config/kde.org"
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}
}
</syntaxhighlight>
</syntaxhighlight>
=== Troubleshooting ===
==== builder for '/nix/store/file-name.service.drv' failed to produce output path for output 'out' at '/nix/store/file-name.service' ====
This can happen if your NixOS version is later than your Home-Manager version (ex. NixOS 22.05 with Home-Manager 21.11). See https://github.com/nix-community/impermanence/issues/95.




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[https://grahamc.com/blog/erase-your-darlings https://grahamc.com/blog/erase-your-darlings] - Explaining why you might want to do this. Uses ZFS snapshots instead of tmpfs.
[https://grahamc.com/blog/erase-your-darlings https://grahamc.com/blog/erase-your-darlings] - Explaining why you might want to do this. Uses ZFS snapshots instead of tmpfs.
https://web.archive.org/web/20241007130142/https://mt-caret.github.io/blog/posts/2020-06-29-optin-state.html - Encypted Btrfs Root with Opt-in State on NixOS. Uses Btrfs instead of tmpfs or ZFS.
Retrieved from "https://wiki.nixos.org/wiki/Impermanence"