Add `nix nario` command to replace `nix-store --export/--import` by edolstra · Pull Request #13969 · NixOS/nix

edolstra · 2025-09-12T14:17:37Z

Motivation

The new CLI still lacks equivalents for nix-store --export and nix-store --import. This adds a subcommand nix nario with the following operations:

nix nario export: Replaces nix-store --export. It requires a --format flag to specify the desired nario version. Currently only 1 is supported. I have another PR incoming (DeterminateSystems@555b2a5) that introduces a new version that adds missing metadata (like signatures) and can be unpacked in constant memory.
nix nario import: Replaces nix-store --import.
nix nario list: Had no equivalent in the old CLI. It shows the contents of a nario file.

In the old CLI, we lacked a name for the file format used by nix-store --export/--import. @cole-h suggested nario analogously to cpio, since it's a concatenation of NARs with some metadata.

Context

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This replaces `nix-store --export` and `nix-store --import`.

xokdvium · 2025-09-12T19:40:04Z

src/libstore/export-import.cc

+static const uint32_t exportMagicV1 = 0x4558494e;

-void exportPaths(Store & store, const StorePathSet & paths, Sink & sink)
+void exportPaths(Store & store, const StorePathSet & paths, Sink & sink, unsigned int version)


Could version be an enum instead? That would be slightly more self-documenting.

Malix-Labs · 2025-09-12T21:23:22Z

That is great, but what does "nario" mean?

cole-h · 2025-09-12T21:32:39Z

Just like cpio was derived from "copy in and out" (according to Wikipedia), one could imagine nario being "NAR in and out".

Mic92 · 2025-09-13T08:34:00Z

src/nix/nario-export.md

+* Export the closure of building `nixpkgs#hello`:
+
+  ```console
+  # nix nario export --format 1 -r nixpkgs#hello > dump


Maybe useful?

Suggested change

# nix nario export --format 1 -r nixpkgs#hello > dump

# nix nario export --format 1 -r nixpkgs#hello > dump

# nix nario export --format 1 -r nixpkgs#hello | zstd > dump.zst

Mic92 · 2025-09-13T08:34:38Z

src/nix/nario-export.md

+  It can be imported in another store:
+
+  ```console
+  # nix nario import < dump


Suggested change

# nix nario import < dump

# nix nario import < dump

# zstd -d < dump | nix nario import

Mic92 · 2025-09-13T08:41:08Z

src/nix/nario.cc

+
+            ref<Store> openStore() const override
+            {
+                abort();


Suggested change

abort();

throw Error('ListingStore cannot be opened');

Mic92 · 2025-09-13T08:41:43Z

src/nix/nario.cc

+    void run(ref<Store> store) override
+    {
+        FdSource source(getStandardInput());
+        importPaths(*store, source, NoCheckSigs); // FIXME


Should be addressed or replaced by a better comment what needs to be fixed here.

roberth

That is great, but what does "nario" mean?

Just like cpio was derived from "copy in and out" (according to Wikipedia), one could imagine nario being "NAR in and out".

For cpio that works out, because it encodes all the things a cp command would copy.
In our case, that does not apply. A NAR only encodes a file system object; not a store object, so the name is misleading. It suggests that the command is only sufficient for nix nar operations, but it unlike those commands, it must interact with a store.

It's a different sce-nario. ~~(Sorry, couldn't help it, but it wasn't enough to get rid of "it's a-me, nario")~~

~~Please consider assigning a more accurate name.~~

Ok, I'll admit defeat. I will embrace the Nario name.

Mic92 · 2025-09-14T18:26:08Z

nix closure import|export|list
nix nar-closure import|export|list

edolstra · 2025-09-15T16:25:17Z

@Mic92 I considered "nix-closure" or something like that, but the problem is that it's not necessarily a closure (namely if you don't pass -r).

roberth · 2025-09-17T21:23:40Z

The command could be nix store export?

Maybe slightly misphrased issue? Add nix store import and nix store export commands to work with nar/narinfo #9038

For the format, if it's not a closure, it's still a set, so a store path set.
Alternatively, the format could be Legacy Store Export, because we'll have a new extensible one
We should probably require the format to be specified explicitly so that a new and/or extensible/self-describing format can be made the default later; otherwise the CLI will be stuck on a bad default forever.
See

Add nix store import and nix store export commands #9474 (comment)

myclevorname · 2025-10-18T01:07:13Z

Please document the file format in the manual.

roberth · 2025-11-03T19:35:49Z

You can now document binary formats in a formal/machine readable way!

Add documentation for NAR spec in kaitai #14345

a-h · 2025-11-11T11:34:01Z

Would I expect to be able to take a devShell from one machine to another like this?

nix nario export --format 2 --recursive `nix eval --raw .#devShells.x86_64-linux.default` > devShell.nario

Copy the flake source code and the devShell.nario to the other machine, then run:

nix-store --import < devShell.nario
nix develop

And I'd have a shell? If so, it's worth adding pkgs.bashInteractive from the flake's input nixpkgs is also included for devShell outputs because the Nix CLI uses it

nix/src/nix/develop.cc

Lines 656 to 664 in 091c0a9

    
           auto bashInstallable = make_ref<InstallableFlake>( 
        
               nullptr, //< Don't barf when the command is run with --arg/--argstr 
        
               state, 
        
               std::move(nixpkgs), 
        
               "bashInteractive", 
        
               ExtendedOutputsSpec::Default(), 
        
               Strings{}, 
        
               Strings{"legacyPackages." + settings.thisSystem.get() + "."}, 
        
               nixpkgsLockFlags);

and it might not be available on the target machine.

edolstra · 2025-11-12T20:47:18Z

@a-h Yes, something like that should work. Though you probably want to use nix develop --profile ./bla --command true, copy the closure of the ./bla symlink, and on the remote machine do nix develop <storepath>. That way Nix doesn't need to build the top-level derivation of the dev shell.

nwf · 2026-02-16T05:29:44Z

tests/functional/export.sh

 outPath=$(nix-build dependencies.nix --no-out-link)

 nix-store --export $outPath > $TEST_ROOT/exp
+nix nario export --format 1 "$outPath" > $TEST_ROOT/exp2


Here and below, $TEST_ROOT is inconsistently quoted. See 230da1c .

nwf · 2026-02-16T06:05:31Z

src/nix/nario.cc

+            }
+        };
+
+        struct ListingStore : Store


This looks like it needs to catch up with #14049 and #14127

Add nix nario command

c8633ce

This replaces `nix-store --export` and `nix-store --import`.

edolstra requested a review from Ericson2314 as a code owner September 12, 2025 14:17

github-actions bot added documentation new-cli Relating to the "nix" command with-tests Issues related to testing. PRs with tests have some priority labels Sep 12, 2025

edolstra mentioned this pull request Sep 12, 2025

CLI stabilization effort #7701

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This was referenced Sep 26, 2025

Args::Flag: Add required attribute #14087

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Add nix nario command DeterminateSystems/nix-src#215

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src/nix/nario.cc

}

};

struct ListingStore : Store

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This looks like it needs to catch up with #14049 and #14127

	# nix nario export --format 1 -r nixpkgs#hello > dump
	# nix nario export --format 1 -r nixpkgs#hello > dump
	# nix nario export --format 1 -r nixpkgs#hello \| zstd > dump.zst

	# nix nario import < dump
	# nix nario import < dump
	# zstd -d < dump \| nix nario import

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edolstra commented Sep 12, 2025

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