All we need is `SystemError`, and the various ways to construct it can
be done with static methods that are more informative. Catching the
derived classes was a footgun that is now impossible, because one can
only has `SystemError` to catch.
I did however make `SysError` and `WinError` top-level function
wrappers in order to avoid churn in the vast majority of call sites.
- Make `descriptorToPath` cross-platform (renamed from
`windows::handleToPath`). Uses `/proc/self/fd` on Linux and
`F_GETPATH` on macOS. Add `HAVE_F_GETPATH` meson check.
This is based on 7226a116a0, which was
removed in 479c356510, but is now
introduced more judiciously.
- Unix error messages in `readFull`, `writeFull`, `readLine` now include
file paths via `descriptorToPath`.
- Convert `std::filesystem::filesystem_error` to `SystemError`
Wrappers like `readLink`, `createDirs`, `DirectoryIterator`, etc. now
catch `std::filesystem::filesystem_error` and rethrow as `SystemError`
with the error code preserved. This ensures consistent exception types
throughout the codebase.
Call sites that previously caught `filesystem_error` and rethrew with
`throw;` now throw `SystemError(e.code(), ...)` instead.
Some call sites can stop catching `filesystem_error` at all,
because they only call the wrapped functions.
- Rework `SystemError` constructors to auto-append error message
The public `SystemError(std::error_code, ...)` constructor now
automatically appends `errorCode.message()` to the error message.
A protected constructor takes an explicit error message string for
subclasses.
`SysError` delegates to the protected constructor with `strerror(errNo)`.
`WinError` delegates with `renderError(lastError)` (now static).
This removes the need to manually append `e.code().message()` at call
sites when converting `filesystem_error` to `SystemError`.
- Use perfect forwarding (`Args &&...` with `std::forward`) consistently
in `BaseError`, `SystemError`, `SysError`, and `WinError` constructors.
Co-authored-by: Sergei Zimmerman <sergei@zimmerman.foo>
In 3df91bea62 I forgot that the header
might get included out-of-tree with -Wundef. Let's make this a public
config option for libutil as it can affect function bodies in headers.
`tryToBuild` threaded a single `PathLocks outputLocks` by reference
across all build phases and managed a `std::unique_ptr<Activity> actLock`
with explicit `if (!actLock)` guards and `.reset()` calls around the hook
retry loop. This commit introduces coroutine lambdas for the three phases:
`tryHookLoop` owns a `PathLocks` in a scoped block for the first attempt
and per-iteration in the retry loop, `tryBuildLocally` acquires its own
`PathLocks`, and the hook-wait `Activity` is a stack variable scoped to
the postpone block.
When `max-jobs = 0` and no remote builders are available, Nix reported
"required system or feature not available" even though the system and
features matched fine. The `canBuildLocally` lambda returned a plain
`bool`, conflating a configuration knob (`max-jobs = 0`) with actual
incompatibility (wrong platform, missing features). It also short-circuited
on the first failing check, so a user with both a platform mismatch and
missing features would only see one of the two.
This commit replaces the bool with a `LocalBuildRejection` struct whose
`WrongLocalStore` variant collects all applicable failures into
`badPlatform`, `missingFeatures`, and an orthogonal `maxJobsZero` flag.
Platform mismatch and missing features now produce separate error
paragraphs, and all applicable reasons appear in a single message.
The local-build capability check also now returns
`std::variant<LocalBuildCapability, LocalBuildRejection>`, bundling
the `LocalStore &` and optional `ExternalBuilder *` together.
This comes in two parts: a `nix store roots-daemon` command that
can run as root and list runtime roots,
and client logic to find runtime roots for a `LocalStore` by connecting
to that daemon.
This may be useful with an unprivileged nix daemon, as it would
otherwise be unable to find runtime roots from process open files
and maps.
Using nix::unreachable() in getInternalType() and type() turns
out to be quite expensive and prevents inlining. Also Value::type
got compiled to a jump table which has a high overhead from indirect
jumps. Using an explicit lookup table turns out to be more efficient.
This does mean that we lose out on nice diagnostics from nix::unreachable
calls, but this code is probably one of the hottests functions in the whole
evaluator, so I think the tradeoff is worth it. The nixUnreachableWhenHardened
boils down to nix::unreachable when UBSan is enabled so we still have good
coverage there.
This makes sure that ExprVar::eval inlines lookupVar call. In practice
this seems to reduce instruction count by ~2%, though it doesn't have
a statistically significant impact on the wall time.
This reduces the churn when changing up the order of
values in a follow-up commit. This should have been done
from the start ideally to improve readability.
The external-builders test expands `$PATH` into a heredoc without quotes,
so any `PATH` entry containing spaces causes bash to parse the line as a
command instead of an assignment, failing the test.
The tab completion handler in `completePrefix` only caught `ParseError`,
`EvalError`, `BadURL`, and `FileNotFound`. Other error types like
`JSONParseError` (which derives from `Error`, not `EvalError`) escaped
the catch block and propagated through editline's C code as undefined
behavior, crashing the REPL. This happened when tab-completing
expressions like `(builtins.fromJSON "invalid").` where evaluation
throws a non-`EvalError` exception.
This commit marks `completionCallback` and `listPossibleCallback` as
`noexcept` with function-try-blocks that catch all exceptions at the
C/C++ boundary, preventing any exception from reaching editline.
Fixes#15133.
When a URL like `github:nixos/nixpkgs/nixpkgs.git?ref=<hash>` (using
`ref` instead of `rev`) failed the github input scheme, it fell
through to `parsePathFlakeRefWithFragment` which constructed a `path:`
`ParsedURL` with an empty authority but a relative path. This violated
RFC 3986 section 3.3 (authority present requires path starting with
`/`), causing an assertion failure in `renderAuthorityAndPath` when
`PathInputScheme` tried to format the URL for an error message.
This commit only sets the authority on absolute paths. Relative paths
get `std::nullopt` for authority, which is the correct representation
per the URL spec.
Fixes#15196. Fixes#14830.
`file-descriptor.{cc,hh}` was getting too big, split out
`file-system-at.{cc,hh}` for the FD-based file system stuff,
`file-descriptor.{cc,hh}` will only be for the fundamental primitives
that are file-system agnostic and work on almost all file types.
Review with `git show --color-moved` to see that this is indeed all
moving.
Docker 28+ defaults to the containerd image store, which pushes layers
uncompressed instead of gzip. The GHA runner image updated Docker to
29.x (actions/runner-images#13633), causing the `nixos/nix:2.33.3`
image to balloon from 138 MB to 505 MB, with all 70 layers pushed as
`application/vnd.docker.image.rootfs.diff.tar` instead of `.tar.gzip`.
OCI clients that only support gzip (e.g. `go-containerregistry`, used
by Concourse CI) fail with "gzip: invalid header".
This commit disables the containerd snapshotter in the release workflow
before any Docker operations, restoring the classic storage driver that
preserves gzip compression through the `docker load` / `docker push`
pipeline.
Fixes#15246
Linux, macOS, and all 3 BSDs have it (according to man page google
search), so let's just drop this. Support for not having it was added in
d03f0d4117 in 2006, things have changed in
the last 20 years!
When ref::cast() fails, the error message was cryptic ("null pointer
cast to ref"). Now it throws a proper bad_ref_cast (a std::bad_cast
subclass) with a clear message showing the actual types involved:
ref<nix::Base> cannot be cast to ref<nix::Derived>
This also adds a demangle.hh utility.
ref<Derived> was already implicitly convertible to ref<Base>, but the
mechanism was unclear and error messages for rejected downcasts were
more cryptic than necessary. This change:
- Adds RefImplicitlyUpcastableTo concept to constrain the conversion
operator, making the intent explicit and improving error messages
- Documents .cast() and .dynamic_pointer_cast() as alternatives for
explicit downcasting
- Adds unit tests for covariance behavior
The old check rejected any relative path whose first character was a
dot, producing false negatives for valid descendants like `.ssh` or
`.config`. This commit changes the logic such that now it inspects the
first path component via `path::begin()`, only rejects `.` and `..`
rather than anything dot-prefixed. Fixes#15207.
libutil tests were crashing on Windows due to issues finding `environ`.
Replace process creation of `getEnv` with a new `getEnvOs` function that
uses native windows APIs.
Also convert a bunch of `RunOptions` fields to use `OsString` to better
reflect the underlying interfaces.
Co-authored-by: John Ericson <John.Ericson@Obsidian.Systems>
The fake cacert didn't have subjectAltName for 127.0.0.1, so the test
was failing for a different reason. Also `tries` setting wasn't being respected.
There's no callsite specifying it in the request, so just use the one specified
in the FileTransferSettings and remove the fields from the FileTransferRequest.
This commit removes the `nixStore` member from `Settings` and instead
computes the default Nix store directory directly in
`StoreConfigBase::getDefaultNixStoreDir()` from env vars
(`NIX_STORE_DIR`, `NIX_STORE`) or the compile-time default. The method
is made public so callers that previously reached through the global
`settings.nixStore` can use it instead.
Progress on #5638
nix store gc: prints number of paths that would be freed, but not bytes
nix-collect-garbage: ditto
nix-store --gc: retains current behavior
It would be very non-trivial to also compute the bytes that would be
freed, due to hardlinking in the store.
Also adds checking for incompatible mixing of dry-run and max-freed
options.
Resolves#5704
Signed-off-by: Lisanna Dettwyler <lisanna.dettwyler@gmail.com>
This commit inlines `DerivationOptions::willBuildLocally` and
`DerivationOptions::canBuildLocally` into their sole call site in
`DerivationBuildingGoal::tryToBuild`. The `canBuildLocally` logic is now
a lambda capturing the surrounding context, and `willBuildLocally` is
replaced by `drvOptions.preferLocalBuild && canBuildLocally`.
Progress on #5638
Co-authored-by: John Ericson <John.Ericson@Obsidian.Systems>
This commit removes the `getMachines` free function and inlines `Machine::parseConfig({settings.thisSystem}, settings.getWorkerSettings().builders)` at its two call sites in `worker.cc` and `build-remote.cc`. The wrapper just forwarded to `Machine::parseConfig` with global settings, so inlining it removes an unnecessary layer of indirection and makes the global dependency explicit at each call site.
Progress on #5638
Co-authored-by: John Ericson <John.Ericson@Obsidian.Systems>
This commit moves `nixStateDir` and `useXDGBaseDirectories` into a dedicated `ProfileDirsOptions` struct and threads it through the profile directory functions (`profilesDir`, `rootProfilesDir`, `defaultChannelsDir`, `rootChannelsDir`, `getDefaultProfile`) so they no longer read from the global `Settings` object directly. This follows the same pattern as `LocalSettings`, `WorkerSettings`, and `NarInfoDiskCacheSettings`.
Progress on #5638
Co-authored-by: Amaan Qureshi <git@amaanq.com>
This commit moves `ttlNegativeNarInfoCache` and `ttlPositiveNarInfoCache` into a dedicated `NarInfoDiskCacheSettings` struct that `Settings` privately inherits from, following the same pattern as `LocalSettings`, `LogFileSettings`, and `WorkerSettings`.
`NarInfoDiskCache` now takes explicit `NarInfoDiskCacheSettings` and `SQLiteSettings` in its constructor instead of reading from the global. The singleton `getNarInfoDiskCache()` is replaced with a `NarInfoDiskCache::get()` static method that accepts these settings, though they are only used on the first call (subsequent calls return the cached instance regardless of arguments).
Progress on #5638
It was a crude hack that this one low-level function was dependent on
the high-level read-only mode setting --- all the more so because rather
than making derivation writing fail, that setting made it silently
"succeed" why not actually writing the derivation. (Also, for context,
we didn't have an such behavior for any other store-mutating operations,
just for this one function.)
I have gotten rid of the wrapper, and updated the call sites
accordingly.
- For the ones that should remain dependent on this setting, I made this
explicit, and added a comment.
- For others, surrounding operations assumed writability (e.g. we had
written something before, or were about to try to read back the
written derivation after), and so I just made those do the underlying
`Store::writeDerivation` operation.
This makes `acquireUserLock` take an explicit stateDir parameter,
since it was previously reaching into the global settings object
just to read `nixStateDir` for constructing the userpool paths.
Progress on #5638
This commit introduces a `getReadOnly` method on the store config that returns if the current store is read only or not. This is then used in subtitution, so we fail gracefully with a nice error message if only the individual store is read-only.
As a bonus, it gets us one step closer to getting rid of the global because we can use the per-store method instead.
Progress on #5638
S3 binary caches now use virtual-hosted-style URLs by default for
standard AWS endpoints. Path-style endpoints (s3.region.amazonaws.com)
only serve HTTP/1.1, preventing HTTP/2 multiplexing and causing TCP
TIME_WAIT socket exhaustion under high concurrency. Virtual-hosted-style
endpoints (bucket.s3.region.amazonaws.com) support HTTP/2, enabling
multiplexing with the existing CURLPIPE_MULTIPLEX configuration.
Add a new `addressing-style` store option (auto/path/virtual) to control
this behavior. `auto` (default) uses virtual-hosted-style for standard
AWS endpoints and path-style for custom endpoints. `path` forces
path-style for backwards compatibility. `virtual` forces virtual-hosted-
style for all endpoints including custom ones.
Fixes: https://github.com/NixOS/nix/issues/15208
Idle connections in libcurl's connection pool can be silently dropped by
the OS or intermediate firewalls/NATs before they can be reused, forcing
new TCP connections to be created. This is especially problematic for
HTTP/1.1 endpoints where multiplexing is unavailable.
Enable TCP keep-alive with a 60-second idle/interval on all curl easy
handles to prevent idle connection drops and improve connection reuse.
This commit moves `pollInterval`, `maxSubstitutionJobs`, `postBuildHook`, and `logLines` into a dedicated `WorkerSettings` struct that `Settings` privately inherits from, as they are only used by the build worker subsystem. This follows the same pattern as `LocalSettings` and `LogFileSettings`.
This expands to __GCC_DESTRUCTIVE_SIZE, which is also 64 (at least in the x86_64 stdenv).
Let the compiler decide what's the appropriate cache line size is. Also, on aarch64-darwin
the cache line size 128 bytes, so the previous fix didn't actually get rid of false sharing
reliably. Clang does this [1] [2], so it overestimates the sizes somewhat, but that's still enough
for avoiding false sharing on darwin.
[1]: a289341ded/clang/lib/Frontend/InitPreprocessor.cpp (L1331-L1339)
[2]: 6f51f8e0f9/clang/lib/Basic/Targets/AArch64.h (L262-L264)
In the https-store tests, a `TestHttpBinaryCacheStoreConfig` is constructed with a call to format to create the cache uri. This commit adds a constructor to `HttpBinaryCacheStoreConfig` to remove the need for this call, and updates the test type to leverage this so we're no longer manually calling fmt on a string to format the port.
This commit makes `FileTransfer` self-contained by giving it a reference
to `FileTransferSettings` instead of reading from the global. It also
adds an optional `FileTransfer` parameter to `HttpBinaryCacheStore` so
callers can inject their own instance.
The main motivation is test isolation. The HTTPS store tests now create
custom `FileTransferSettings` with the test CA certificate and pass it
through `makeFileTransfer()`, avoiding global state mutation entirely.
nix-nswrapper allows running nix in its own user namespace,
believing it is root and with access to build users for sandboxing
with auto-allocate-uids, while it is actually unprivileged.
It is used to wrap nix, and an example of its use has been
added to the unprivileged daemon functional tests.
Running it does not require any elevated privileges,
only uids and gids allocated in /etc/sub{uid,gid}
The `caFile`, `netrcFile`, and `downloadSpeed` settings are only used by
the file transfer subsystem but lived in the global `Settings` class.
This moves them to `FileTransferSettings` where they belong.
Co-authored-by: Amaan Qureshi <git@amaanq.com>
`hashedMirrors` is only relevant to local builds (it is consumed by
`builtin:fetchurl` during derivation building) but lived in the global
`Settings` class. This moves it to `LocalSettings` where it belongs
and threads it through `BuiltinBuilderContext` so `fetchurl.cc` reads
it from the context instead of reaching into `settings` directly.
The underlying mechanism is now in a new `fetchBuildLog` function I put
in `libcmd`.
I am putting it in here and not in libstore because I have some doubts
about `getDefaultSubstituters`, so I would like to keep it in a more
"peripheral" part of the codebase for now.
The `storeUri`, `substituters`, and `trustedSubstituters` settings now
store typed `StoreReference` values directly instead of raw strings,
so callers work with the real types without manual parsing.
This is a reworked version of #10761.
Instead of constructing a `StoreReference` and letting `openStore()` resolve it,
this commit creates the store config directly and calls `openStore()` on it. This
avoids the indirection through the store registry.
Stores hold their config as `ref<const Config>` or `const Config &`,
so `Setting<>` fields are already immutable after store construction.
The field-level `const` is redundant and prevents pre-construction
mutation which is sometimes useful. This commit updates these settings by dropping the `const` qualifier, as it's not needed.
The CLI flags `--from`, `--to`, `--eval-store`, and substituter URIs now
parse to `StoreReference` at the argument boundary. `fetchClosure` uses
`StoreReference::parse` instead of `parseURL`. This also adds
`operator<=>` to `StoreReference`.
This commit makes `nix daemon` inherit from `StoreConfigCommand`
instead of `Command`, so that it receives a `StoreConfig` to open
and serve stores with. This cleans up a few things (removes
`openUncachedStore` helper, passes `storeConfig` through
`daemonLoop`/`runDaemon` instead of opening stores ad-hoc) and will
allow further cleanups.
It's apparently a common footgun in Linux that the death signal isn't
preserved across calls to setuid/setgid. If nix-build gets SIGKILL-ed
while a build is running that would lead to a runaway build process that
would get reparented to init/systemd.
This is pretty easy to reproduce with the following derivation:
derivation {
name = "pdeathsig-repro";
system = builtins.currentSystem;
builder = "/bin/sh";
args = [
"-c"
''
while :; do :; done
''
];
}
And the reproduction script:
sudo nix-build repro.nix &
sleep 3
BUILDER=$(pgrep -u nixbld1)
sudo kill -9 $(pgrep -f 'nix-build.*repro')
sleep 1
ps -p $BUILDER -o pid,ppid,user,comm
To address this we have to restore the death signal after all the calls
to setuid/setgid. This is done in a helper function preserveDeathSignal
that takes a callback to avoid code duplication.
See: https://github.com/golang/go/issues/9686
This is a fairly simple function, isolated from the rest of libmain
and could be useful if new programs are made that are not part of the
main nix-cli subproject.
This commit extracts the Unix domain socket server loop (`PeerInfo`,
`getPeerInfo`, and the systemd socket activation / poll / accept loop)
from `src/nix/unix/daemon.cc` into a reusable `unix::serveUnixSocket`
function in `libcmd`.
Diagnosed by UBSan in hydra [1]:
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /nix/store/m1k4nxs8r0fl0pjxqp5n37vxgms7gdlb-gcc-14.3.0/include/c++/14.3.0/bits/move.h:234:11 in
+(prefetch.sh:6) path=
++(prefetch.sh:6) onError
++(/build/source/tests/functional/common/functions.sh:241) set +x
prefetch.sh: test failed at:
main in prefetch.sh:6
[1]: https://hydra.nixos.org/build/321098757/nixlog/1
To get `bashInteractive`, `nix develop` currently
[gets a flake reference to nixpkgs](3b473c4be5/src/nix/develop.cc (L650-L658)),
either from [`inputs.nixpkgs`](3b473c4be5/src/libcmd/installable-flake.cc (L204))
or [`<nixpkgs>`](3b473c4be5/src/libcmd/include/nix/cmd/installable-flake.hh (L87)).
Currently, this is done by name for any (locked) reference.
For any `nixpkgs` reference lacking a `flake.nix`, `nix develop` thus errors:
```
error (ignored): path '.../flake.nix' does not exist
```
While the registry does not expose info to help check this,
flake inputs expose the `flake` boolean.
This means that given `inputs.<name>.flake = false;`,
we may know in advance that our reference should not be to a flake.
This change incorporates this, so that given `inputs.nixpkgs.flake = false;`,
`nix develop` will fall back `<nixpkgs>` to use its flake for `bashInteractive`.
While Nixpkgs itself of course does expose a flake,
this check is relevant in particular for dummy inputs
(e.g. inputs using `{ url = "file:/dev/null"; flake = false; }`),
which may be overridden by `--override-input` or `.follows`,
yet do not expose (flake) code themselves.
Signed-off-by: cinereal <cinereal@riseup.net>
Extract the logic for determining whether a derivation should be resolved
before building into a dedicated method. Then use that to not resolve
unnecessarily in `nix-shell`.
The recent conversion of WorkerProto::Version from unsigned int to a
struct exposed a latent issue: `.version = 16` was being interpreted
as aggregate initialization `{.major = 16, .minor = 0}` rather than
the intended wire format value.
This commit adds -Werror=c99-designator to catch this class of bugs at
compile time. (The bug itself was fixed in
7eb23c15f39ca413a5f3cc0d3ab630311b4709be.)
For background:
The hardcoded version was originally the integer 16, which in the old
wire format (major << 8 | minor) meant version 0.16. However, the
version checks only compared minor versions via GET_PROTOCOL_MINOR(),
so this worked by accident.
After the Version struct conversion, the aggregate initialization
{.major = 16, .minor = 0} happened to still work because 16 > 1 in
lexicographic comparison against {1, 16}.
The correct version is {1, 16} because:
- The worker protocol uses major version 1 (all checks are {1, x})
- Version 1.16 is when ultimate/sigs/ca fields were added
- This matches the serialization check `>= {1, 16}`
Fixes abort on :ll if nothing has been loaded yet. Also gets rid of
redundant openStore() calls that were dead code (store can be extracted
from EvalState already) and arguably openStore is a layer violation.
Also catches EPIPE in case the pager gets interrupted to avoid superfluous
error messages.
This commit embeds the negotiated `FeatureSet` directly into `WorkerProto::Version` and introduces a `Number` inner type with total ordering, so that `Version` itself (number + features) only has partial ordering. This is a follow-up to #15155, cleaning up the separate `features` fields on `ReadConn`/`WriteConn`.
Co-authored-by: Amaan Qureshi <git@amaanq.com>
This improves the performance of parseNarListing, which is used by commands
like `nix nar ls` when the underlying source allows cheap seeks (like StringSource
or FdSource that does lseek).
For `nix nar ls` of a NAR for linux source tarball this cuts down the runtime almost
in half (from 300ms -> 175ms).
This commit replaces the `GET_PROTOCOL_MINOR(version)` macros with a proper `WorkerProto::Version` struct. As a bonus, this also fixes some version checks that were incorrectly ignoring the major version number.
Co-authored-by: Amaan Qureshi <git@amaanq.com>
This change is required for implementing the unprivileged garbage collection daemon,
but it may also be useful to reduce code duplication and separate out OS-specific
garbage collector roots implementations in the future.
Caching NAR hashes instead of store paths makes the cache more
general, because we can always compute the store path from the NAR
hash, but not the other way around. This is useful for lazy trees,
where we want to compute the NAR hash of an input with caching.
The global `Settings` struct contained many settings that only apply to
local builds or the local store (sandbox configuration, GC settings,
build user groups, etc.). This commit extracts these into a dedicated
`LocalSettings` struct in its own header, along with `GCSettings` and
`AutoAllocateUidSettings`.
This improves code organization and prepares for eventually making these
per-store settings in the future. Settings are accessed via
`getLocalSettings()` from the global settings object or through
`LocalStoreConfig::getLocalSettings()` for store-specific access.
Useful for commands that need a `StoreConfig` but do not want to open
the store, as a `StoreCommand` would do.
At the same time, make copy commands more clear by making store choice
for `updateProfile` explicit and removing the unused `getDstStore` function
in `StoreCommand`. This was a layer violation, as `StoreCommand` does
not have a concept of a source/destination store distinction.
This is purely a fix to use CreateFileW in mingw builds. Also adds some
FIXMEs for suspicious symlink following on truncation that can probably
be tightened down without any problems (other than nix-channel), but for
now this is a no-op change other than consistently using O_CLOEXEC, which
is harmless.
We now support `LISTEN_FDS` values greater than 1, per the systemd
socket activation spec.
These changes are by @edolstra, taken from #5265. This is just that PR
*without* the TCP parts, which I gathered are the controversial parts.
Hopefully this remainder is not so controversial.
Review with indentation ignored, because some code has moved inside a
new loop but otherwise is mostly unchanged.
aws-sdk-cpp used to include a checksum for uploads (CRC64 since ~September 2025).
Content-MD5 [1] should be universally supported by all s3 compatible services, since the SDK used
to include it unconditionally too.
[1]: https://docs.aws.amazon.com/AmazonS3/latest/API/API_PutObject.html
This commit consolidates the four separate boolean flags
(`permanentFailure`, `timedOut`, `hashMismatch`, & `checkMismatch`) into
a single `ExitStatusFlags` struct with methods for computing exit status
codes and updating from failure status.
The explicit serializer added in
bfdd124837 is the right place to adjust
values for sake of wire protocol compat. The protocol-agnostic `Worker`
code where it was before is the wrong spot.
(That spot was originally chosen because the back compat logic predates
having an explicit serializer for this data type to use instead.)
Co-authored-by: John Ericson <John.Ericson@Obsidian.Systems>
This test insisted on placing profiles in NIX_STATE_DIR, but all
packages were removed from the profile immediately after so they did not
act as garbage collector roots. Switch to directly calling nix-build,
allowing the test to run in VMs without NIX_STATE_DIR.
This commit refactors the `canonicalisePathMetaData` function to take an
options struct instead of individual parameters with platform-specific
`#ifdef`s.
The struct contains a `uidRange` field (Unix only) for build user
ownership validation, and an `ignoredAcls` field for ACLs to skip when
removing extended attributes
Due to a typo in quoteRegexChars, finding runtime garbage collection roots
was failing on paths that contained a dot, or any other regex chars that would
have to be replaced.
When fixing that error, also add tests to make sure gc continues to
work.
This introduces a `PersonalityArgs` struct to pass named arguments to `setPersonality`. The `impersonateLinux26` setting is now passed from the call site rather than read from settings inside the function.
The C++ rule of five suggests that when a custom destructor is needed
then several other functions are as well. The lack of those makes
certain operations challenging
We use a different fstat on posix and windows systems,
and not all fstat users were using the correct one.
Factor out fstat to make the change easier.
See also a13de50df3 for other stat
functions
This cleans up the logic for checking if the worker's store is a valid
local store when we're not hooking it. If we have a local store, we then
pass that as an argument to `DerivationBuildingGoal::buildLocally`,
rather than checking inside the function itself.
The two settings `envKeepDerivations` and `upgradeNixStorePathUrl` were
only used in one command each, so it makes more sense to move them to
their own files. This commit moves them both into a small self-contained
settings struct and registers them with the global config.
Currently, tests fail when the host system has `commit.gpgsign` or
`tag.gpgsign` enabled at the system level (in my case, a custom path
located at `/etc/git/config`), since the signing key is unavailable in
the test sandbox.
The tests set `HOME=$TEST_HOME` to isolate themselves, which bypasses
the user-level git config (`~/.gitconfig`). However, if a user sets the
system-level config via `GIT_CONFIG_GLOBAL` or `GIT_CONFIG_SYSTEM`, it
still applies, causing commits to fail when signing is enabled there.
In this PR, I explicitly set `GIT_CONFIG_GLOBAL` and `GIT_CONFIG_SYSTEM`
to `/dev/null` so that the user's system config is never read from or
written to. I've also replaced `git config --global protocol.file.allow
always` with `GIT_CONFIG_*` environment variables to avoid writing to
`/dev/null`.
The test was checking for `$stdenv` but the `fixed` derivation doesn't
actually have stdenv, it just has `FOO`. I've updated it to check the
value of `FOO` instead.
The settings related to diff hook (`run-diff-hook` and `diff-hook`) are
a little redundant and don't need to be leaked in derivation-builder
when computing the diff hook path to execute.
Instead of directly using both `runDiffHook` and `diffHook` settings in
derivation-builder, we can just encapsulate the logic to determine
whether or not we have a diff hook executable to run in a helper
function. We also mark `handleDiffHook` as static.
- Extract destructor logic into named methods (`deletePath()`,
`unmount()`, and `remove()`) that can be called explicitly. These ones
will throw exceptions normally, unlike the destructor which must quash
them to avoid double-exceptions.
- Use `std::filesystem::path` in `AutoUnmount` (changed from `Path`)
- Remove `del` field from `AutoRemoveJail`, using `INVALID_JAIL`
sentinel value instead.
- Add move assignment operators implemented via friend `swap` functions
for all three RAII classes.
- Remove old `reset(...)` methods that took parameters. These were a bit
misleading --- do they cancel or immediately destroy? --- and doing it
explicitly with cancel and then assignment is not hard.
Co-authored-by: Sergei Zimmerman <sergei@zimmerman.foo>
The previous implementation double-quoted the _args variable by escaping
each argument individually and then wrapping them all in single quotes,
producing output like: _args=''-e' 'arg1' 'arg2''
This fix concatenates all arguments into a single string first, then
escapes that string once, producing correct output like:
_args='-e arg1 arg2'
This prevents potential command injection issues when the output is
sourced in shell scripts.
Fixes#14327
Use wrappers to make error handling easier.
On Windows we are using proper 64-bit time and size info.
We still have the problem of no `lstat` on Windows, but this will be
dealt with in future PRs.
Follows the same pattern as `GCSettings`: extract UID allocation
settings
into a dedicated struct that Settings inherits privately from.
The current settings infrastructure prevents correct data modeling that
would allow `autoAllocateUids` to be a
`std::optional<AutoAllocateUidSettings>`.
To compensate, the getter `getAutoAllocateUidSettings()` returns a
pointer -
nullptr when disabled, providing the optional-like semantics we want.
Co-authored-by: Amaan Qureshi <git@amaanq.com>
settings.buildHook.setDefault was running after nix.conf was parsed,
causing whatever value settings.buildHook had to be clobbered.
Re-arrange the logic so that the default is set before nix.conf is
parsed, so that custom build hooks can be used by specifying them in
nix.conf.
Signed-off-by: Lisanna Dettwyler <lisanna.dettwyler@gmail.com>
This is no longer necessary and produces an eval warning:
> evaluation warning: The 'pie' hardening flag has been removed in favor of enabling PIE by default in compilers and should no longer be used.
This was first introduced in 2200f315da, but
is no longer necessary since the switch to meson.
Previously AWS CRT logs went directly to stderr via ApiHandle::InitializeLogging,
causing log spam that didn't respect Nix's verbosity settings.
This implements a custom aws_logger using the aws-c-common C API that:
- Routes all AWS logs through nix::logger
- Maps AWS log levels conservatively (ERROR/WARN -> lvlInfo) since the SDK
treats expected conditions like missing IMDS as errors
- Prefixes messages with (aws) for clarity
- Respects Nix's verbosity flags (-v, -vv, etc.)
This unsures that we call the correct virtual functions when destroying a particular
DerivationBuilder.
Usually the order of destructors is in the reverse order of inheritance:
ChrootLinuxDerivationBuilder -> ChrootDerivationBuilder -> DerivationBuilderImpl
autoDelChroot was being destroyed before the DerivationBuilderImpl::killChild was
run and it would fail to clean up the chroot directory, since there were still processes
writing to it. Note that ChrootLinuxDerivationBuilder::killSandbox was never run in
the interrupted case at all, since virtual functions in destructors do not call derived class
methods.
I could reproduce the issue with the following derivation:
let
pkgs = import <nixpkgs> { };
in
pkgs.runCommand "chroot-cleanup-race" { } ''
mkdir -p $out
for i in $(seq 1 200); do
(
mkfifo $out/fifo$i
cat $out/fifo$i > /dev/null &
while true; do
: > $out/file$i
done
) &
done
sleep 0.05
echo done > $out/main
''
While interrupting it manually when it would hang.
Wrapping the unique pointer in a custom deleter function we can run all
of the necessary clean up code consistently and calling the right virtual
functions. Ideally we'd have a lint that bans the usage of virtual functions
in destructors completely.
This addresses the concerns with network isolation that have been raised
previously [1] by only running the tests by default in a network namespace.
This way all networks tests are independent of each other and do not bind
to ports in the host namespace.
This is much neater than doing these sorts of tests in functional suite.
[1]: https://github.com/NixOS/nix/pull/14266#issuecomment-3411261285
Don't add the whole store to sandbox-paths unconditionally. Exposing
the entire store defeats the purpose of sandboxing, and when the test
store is the same as the system store (NixOS VM), it causes an obscure
"Permission denied" error.
Only add sandbox-paths when not on NixOS, indicating a separate test
store that needs access to system store build tools.
All current NixOS functional VM tests have a daemon as root with the
tests running as different unprivileged users.
The new `functional_unprivileged-daemon` test runs the daemon and the
nix functional tests as separate unprivileged users.
Users may want to run an unprivileged daemon on non-NixOS systems
where the administrator does not fully trust nix, but multiple users
want to use nix for their own purposes. It could also be useful in
concert with an overlay-mount store, where the nix daemon cannot
modify the derivations used by the system, and thus a nix vulnerability
would not lead to root code execution.
When running nix as an unprivileged user it may not be able to write to
all paths in the nix store. Ignore deletion failures to fix tests that
run `nix-collect-garbage` in this configuration.
Co-Authored-By: John Ericson <John.Ericson@Obsidian.Systems>
We are now seeing. I guess we are out with the cache. When the API responds with 418 (I'm a teapot)
it seems like the only reasonable solution is to oblige.
error: unable to download 'http://127.0.0.1:37515/7ms9f25xyxavf32pvdc3vb28nzzmkbn3.narinfo': HTTP error 418
response body:
GitHub API error: GitHub Actions Cache throttled Magic Nix Cache. Not trying to use it again on this run.
This means that `RestoreSink` can work in the TOCTOU-resilliant way on
Windows too. And it also bodes will for the upcoming OS source accessor
improvements.
A few misc little refactors around error handling and whatnot are done
along the way too. (No more attempt to support pre Windows Vista! lol.)
This cannot be realiably automatically tested until we have a newer
version of Wine, but it does build, so I am inclined to say we just try
it for now.
This PR follows the same approach as #15043 and the
[`LogFileSettings`](https://github.com/NixOS/nix/pull/15051)
extraction:
- `GCSettings` struct inherits from virtual `Config`
- `Settings` privately inherits from it
- Accessed through `getGCSettings()`
The new method on `LocalStoreConfig` anticipates on making these
settings per-store. 0b606aad46 added both
the autoGC and periodic wakeups, which is why we think they are related.
When an upload fails with a transient HTTP error (e.g., S3 rate limiting
with HTTP 503), retries would fail with "curl error: Failed to open/read
local data from file/application" because the upload source was already
exhausted from the previous attempt.
Restart the source in init() to ensure it's at the beginning for both
first attempts (no-op) and retries (necessary fix).
Fixes: #15023
Progress on #5638
Replace the SQLite constructor's mode parameter with a Settings struct
that includes both the open mode and useWAL flag. This makes the
dependency on useSQLiteWAL explicit at call sites rather than having
it read from the global settings inside the constructor.
All call sites now explicitly pass settings.useSQLiteWAL, preparing
for downstream work where stores can pass their own settings instead
of relying on the global.
Some S3-compatible services (like GCS) modify the Accept-Encoding header
in transit, which breaks AWS SigV4 signature verification since curl's
implementation signs all headers including Accept-Encoding.
Fixes: #15019
It is possible that the `nix` executable is installed but not `nix-env`
(this may be unusual but for example in Fedora we have a separate
`nix-legacy` subpackage, which includes the `nix-env` symlink).
The current error message:
```
$ nix config check --verbose
Running checks against store uri: local
[FAIL] Multiple versions of nix found in PATH:
```
when there is no nix-env in PATH is confusing.
This change makes the error message precise for the missing nix-env case.
Use
```
git show --color-moved --patience --color-moved-ws=ignore-all-space
```
to review and see that this is mostly code motion.
Co-Authored-By: John Ericson <John.Ericson@Obsidian.Systems>
Introduce a new `Signature` struct that represents a cryptographic
signature
along with the key name that produced it. This provides:
- Structured representation instead of colon-separated strings
- Type-safe parsing with `Signature::parse()`
- Serialization with `to_string()`
- JSON serialization/deserialization
- Batch parsing with `parseMany<Container>()`
- Batch serialization with `toStrings()`
This is scaffolding for future changes that will use this type
throughout the codebase.
This will once and for all get rid of all double-quoting issues. On windows the quoting
is doubly bad because it escaped all \ to \\, which is very bad for error messages. In
order to prevent future regression std::filesystem::path formatting now must use a special
type PathFmt (like Magenta). In the future we could even change how we render filesystem paths.
Instead of the stringly typed code we should use an enum class, this is
more clear and less error-prone. Also adds settings implementations for
CompressionAlgo and std::optional<CompressionAlgo>. The first is used
for NAR compression, since we never accepted empty strings there:
error: unknown compression method ''
The other one is used for optional .narinfo, .ls, and log/ compression.
Those treated empty strings as compression being disabled. The same exact
semantics is kept.
This has the benefit of improving error messages for incorrect values:
error: option 'compression' has invalid value 'bz'
Did you mean one of br, xz or lz4?
The docs were out of date. Since 8a0c00b856 Nix
supports all compression algorithms exposed by libarchive (if it's built with
native support for them). Let's be honest about it in the docs.
This avoids the wall of text like, because ThreadPool doesn't print interrupts
on shutdowns.
error (ignored): opening a connection to remote store 'ssh-ng://127.0.0.1' previously failed
error (ignored): opening a connection to remote store 'ssh-ng://127.0.0.1' previously failed
error (ignored): opening a connection to remote store 'ssh-ng://127.0.0.1' previously failed
error (ignored): opening a connection to remote store 'ssh-ng://127.0.0.1' previously failed
error (ignored): opening a connection to remote store 'ssh-ng://127.0.0.1' previously failed
error (ignored): opening a connection to remote store 'ssh-ng://127.0.0.1' previously failed
error (ignored): opening a connection to remote store 'ssh-ng://127.0.0.1' previously failed
Without this we can abort by throwing an exception in the destructor:
[24/635/2958 copied (3.8/26.0 GiB)] copying path '/nix/store/ncd2iic2nwxwhqsf4gp9sdybkwnwz20b-ruby3.3-mini_portile2-2.8.9' from 'ssh-ng://localhost:22'
Nix crashed. This is a bug. Please report this at https://github.com/NixOS/nix/issues with the following information included:
Exception: nix::Interrupted: error: interrupted by the user
Stack trace:
0# 0x00000000004AFFE9 in result/bin/nix
1# 0x00007F946290A1AA in /nix/store/cf1a53iqg6ncnygl698c4v0l8qam5a2q-gcc-14.3.0-lib/lib/libstdc++.so.6
2# __cxa_call_terminate in /nix/store/cf1a53iqg6ncnygl698c4v0l8qam5a2q-gcc-14.3.0-lib/lib/libstdc++.so.6
3# __gxx_personality_v0 in /nix/store/cf1a53iqg6ncnygl698c4v0l8qam5a2q-gcc-14.3.0-lib/lib/libstdc++.so.6
4# 0x00007F946283FA19 in /nix/store/cf1a53iqg6ncnygl698c4v0l8qam5a2q-gcc-14.3.0-lib/lib/libgcc_s.so.1
5# _Unwind_RaiseException in /nix/store/cf1a53iqg6ncnygl698c4v0l8qam5a2q-gcc-14.3.0-lib/lib/libgcc_s.so.1
6# __cxa_throw in /nix/store/cf1a53iqg6ncnygl698c4v0l8qam5a2q-gcc-14.3.0-lib/lib/libstdc++.so.6
7# 0x00007F94635D82D0 in /nix/store/9wrnk0nizdwba4sy9lg3h0xd30pg1x5a-nix-util-2.34.0pre/lib/libnixutil.so.2.34.0
8# nix::Pid::wait() in /nix/store/9wrnk0nizdwba4sy9lg3h0xd30pg1x5a-nix-util-2.34.0pre/lib/libnixutil.so.2.34.0
9# nix::Pid::~Pid() in /nix/store/9wrnk0nizdwba4sy9lg3h0xd30pg1x5a-nix-util-2.34.0pre/lib/libnixutil.so.2.34.0
forced_unwind is thrown by Boost.Context when destroying the coroutine.
This lead to us resetting the remote connection for each narFromPath
with the ssh-ng:// store, so copying was very slow.
This makes all addToStore operations that use these source accessors
constant memory regardless of file sizes. Also make the other overload
altogether and relegate it to the base class as a non-virtual method to
avoid such mistakes.
This factors out the helper function from seekableGetNarBytes into copyFdRange
and adds some more sanity checks for offset/length truncation/wrapping at that
API boundary where we work with NAR-style offsets and convert to native off_t.
Instead of mutating the file pointer we can instead safely do
preads. That makes the local-nar-info cache once again thread safe
without the overhead of reopening the file that we used to have prior
to b9b6defca6 which broke the thread safety
by persisting the file descriptor.
Without the change the build fails for me as:
../unix/file-descriptor.cc:404:70: error: 'RESOLVE_BENEATH' was not declared in this scope
404 | dirFd, path.rel_c_str(), flags, static_cast<uint64_t>(mode), RESOLVE_BENEATH | RESOLVE_NO_SYMLINKS);
| ^~~~~~~~~~~~~~~
This happens for 2 reasons:
1. `__NR_openat2` constant was not pulled in from the according headers
and as a result `<linux/openat2.h>` was not included.
2. `define HAVE_OPENAT2 0` build is broken: refers to missing
`RESOLVE_BENEATH` normally pulled in from `<linux/openat2.h>`
This changes fixes both.
Document the nix-cache-info file format used by binary caches, including
the StoreDir, WantMassQuery, and Priority fields, their behavior, and
links to related store options.
This is the usual conventions on windows.
See https://learn.microsoft.com/en-us/windows/win32/shell/knownfolderid and
https://github.com/adrg/xdg for examples of the mapping of XDG paths to Windows
known folders.
Additionally, on Windows, this allows us to dispense with a hard-coded
default for `nixConfDir`, which is both nice (fewer compile-time
configuration options) and necessary, because we don't know what drive
the `ProgramData` directory will live on.
Tested on wine.
Co-Authored-By: John Ericson <John.Ericson@Obsidian.Systems>
The test data was using invalid signature strings like "asdf" and
"qwer" which don't follow the required "name:base64signature" format.
This updates them to use properly formatted signatures with valid
base64-encoded data.
Document the Nix32 base-32 variant used for store path digests and
hash output. The new page covers:
- The 32-character alphabet (omitting e, o, u, t)
- Byte order differences from base-16 encoding
Also update references throughout the manual to link to the new page.
Change "cannot build missing derivation" to "failed to obtain derivation of"
since the path (e.g. '...drv^out') is a derivation output, not a derivation.
The message could be improved further to resolve ambiguity when multiple
outputOf links are involved, but for now we err on the side of brevity
since this message is already merged into larger error messages with
other context from the Worker and CLI.
When !keepGoing and a goal fails, other goals are cancelled and
remain with exitCode == ecBusy. These cancelled goals have a default
BuildResult::Failure{} with empty errorMsg.
Previously, buildPathsWithResults would return these cancelled goals,
and throwBuildErrors would report them as failures. When only one such
cancelled goal was present, it would throw an error with an empty
message like:
error: build of '/nix/store/...drv^*' failed:
Now we skip goals with ecBusy since their state is indeterminate.
Cancelled goals could be reported, but this keeps the output relevant.
Other indeterminate goal states were already not being reported, for
instance: derivations that weren't started for being blocked on a
concurrency limit, or blocked on a currently building dependency.
When keepGoing=false and a build fails, other goals are cancelled.
Previously, these cancelled goals were reported in the "build of ...
failed" error message alongside actual failures. This was misleading
since cancelled goals didn't actually fail - they were never tried.
Update the test to expect only the actual failure (hash mismatch) to
be reported, not the cancelled goals.
DerivationTrampolineGoal is the top-level goal whose buildResult is
returned by buildPathsWithResults. When it failed without setting
buildResult.inner, buildPathsWithResults would return failures with
empty errorMsg, producing error messages like:
error: failed to build attribute 'checks.x86_64-linux.foo',
build of '/nix/store/...drv^*' failed:
(note the empty message after "failed:")
Use the new doneFailure helper to ensure buildResult is populated
with meaningful error information.
There can be a long time between the creation of `TransferItem` and
the start of the curl download, which can lead to misleading download
durations and progress bar status. So now we create the `Activity` and
update `startTime` when curl actually starts the download.
Previously, calling queryValidPaths() with a large number (e.g. 100K)
of store paths failed because Nix immediately creates a `TransferItem`
for each .narinfo, which is then registered as a handle with
curl. However curl appears to scale poorly internally: even though
only a few downloads are actually started (up to the
connections/streams limits), it spends a lot of CPU time dealing with
the inactive handles. So the curl thread is sitting at 100% CPU, the
active downloads stall and time out, and everything grind to a halt.
So now we limit the number of curl handles to http-connections *
5. With this, fetching 100K .narinfo files from localhost succeeds in
~15 seconds.
This operation has been deprecated since
09a6321aeb (July 2012). It was used by
client versions <= 11, which is below `MINIMUM_PROTOCOL_VERSION`
(currently 18).
We can get rid of `NarMember`, because it is just `NarListing` in
disguise! The use of `std::variant` makes clear that certain stat fields
we don't care about in the non-regular-file case too.
Relative paths (e.g., "relative/repo") would crash in renderAuthorityAndPath()
because an empty authority was set, violating RFC 3986 section 3.3 which
requires paths to start with "/" when an authority is present.
Fix by only setting authority for absolute paths:
- Absolute paths: file:///path (empty authority)
- Relative paths: file:path (no authority)
Also reject SCP-like URLs without a user (e.g., "github.com:path") with a
clear error message, since proper support requires careful implementation,
which is not something I can do right now.
Relative paths like `file:./foo.tar.gz` have never worked for tarballs
because curl rejects relative file: URLs. Previously this resulted in
cryptic curl errors. Now we reject them early with a clear message
explaining that relative paths are not supported because there is no
defined base directory to resolve them against.
See https://github.com/NixOS/nix/issues/12281
When a goal with an active child process is destroyed (e.g., during
failure cascades without `--keep-going`), the child process gets killed
but `childTerminated` was never called. This left stale entries in the
worker's `children` list.
Fix this by ensuring `childTerminated` is called from destructors:
- `DerivationBuilderImpl::killChild` now calls `childTerminated` via
the `miscMethods` callback.
- `HookInstance` gains an `onKillChild` callback that is invoked from
its destructor when killing the process. `buildWithHook` sets this
callback to call `childTerminated`.
To make these calls safe from destructors (where the goal object may be
partially destroyed), add a new overload of `Worker::childTerminated`
that takes an explicit `JobCategory` parameter instead of calling the
virtual method `Goal::jobCategory`. The original overload still exists
for convenience for normal (non-destructor) call sites.
Add helpers to the base Goal class that set buildResult and call amDone,
ensuring buildResult is always populated when a goal terminates.
Derived class helpers now call the base class versions. This reorders
operations: previously buildResult was set before bookkeeping (counter
resets, worker stats), now it's set after. This is safe because the
bookkeeping code (mcExpectedBuilds.reset(), worker.doneBuilds++,
worker.updateProgress(), etc.) only accesses worker counters, not
buildResult.
It correctly models the is-a relation. This will be useful for doing a dynamic_cast in
downstream code that wants to copy from a file descriptor to a file descriptor.
Nix currently doesn't do any resource control, and Delegate=yes turns on all the controllers.
In particular, this enables using cpusets with cgroups V1 alongside the Nix daemon.
This also adds a utility for opening a file descriptor from a path in readonly mode.
Previous commit helps a bit with error handling, since now we just throw a NativeSysError.
This way each consumer of NativeSysError doesn't have to
also conditionally include the windows-error.hh, which is very cumbersome.
And we can't include windows-error.hh in error.hh because of a circular import.
Previously builtins.readDir would return an empty attribute set
instead of barfing on non-existent paths. This is a regression from
2.32 for impure eval.
This makes the logic much easier to follow. Unlike before, the use of
separate functions is not making us pass a gazillion arguments or use
the crutch of class variables.
There was a bunch of logic in there which was, effectively, using the
build hook, rather than deciding *whether* to use the build hook. We
want it to only be the latter.
synopsis: "New setting `ignore-gc-delete-failure` for local stores"
prs: [15054]
---
A new local store setting [`ignore-gc-delete-failure`](@docroot@/store/types/local-store.md#store-local-store-ignore-gc-delete-failure) has been added.
When enabled, garbage collection will log warnings instead of failing when it cannot delete store paths.
This is useful when running Nix as an unprivileged user that may not have write access to all paths in the store.
This setting is experimental and requires the [`local-overlay-store`](@docroot@/development/experimental-features.md#xp-feature-local-overlay-store) experimental feature.
synopsis: New command `nix store roots-daemon` for serving GC roots
prs: [15143]
---
New command [`nix store roots-daemon`](@docroot@/command-ref/new-cli/nix3-store-roots-daemon.md) runs a daemon that serves garbage collector roots over a Unix domain socket.
It enables the garbage collector to discover runtime roots when the main Nix daemon doesn't have `CAP_SYS_PTRACE` capability and therefore cannot scan `/proc`.
The garbage collector can be configured to use this daemon via the [`use-roots-daemon`](@docroot@/store/types/local-store.md#store-experimental-option-use-roots-daemon) store setting.
This feature requires the [`local-overlay-store` experimental feature](@docroot@/development/experimental-features.md#xp-feature-local-overlay-store).
@@ -338,7 +338,7 @@ Here is more information on the `output*` attributes, and what values they may b
This will specify the output hash of the single output of a [fixed-output derivation].
The `outputHash` attribute must be a string containing the hash in either hexadecimal or "nix32" encoding, or following the format for integrity metadata as defined by [SRI](https://www.w3.org/TR/SRI/).
The "nix32" encoding is an adaptation of base-32 encoding.
The ["nix32" encoding](@docroot@/protocols/nix32.md) is Nix's variant of base-32 encoding.
To check whether it works, try the following on the client:
To check whether it works, try fetching the [`nix-cache-info`](@docroot@/protocols/nix-cache-info.md) file on the client:
```console
$ curl http://avalon:8080/nix-cache-info
StoreDir: /nix/store
WantMassQuery: 1
Priority: 30
```
which should print something like:
StoreDir: /nix/store
WantMassQuery: 1
Priority: 30
When writing to a binary cache (e.g., with [`nix copy`](@docroot@/command-ref/new-cli/nix3-copy.md)), Nix creates [`nix-cache-info`](@docroot@/protocols/nix-cache-info.md) automatically if it doesn't exist.
On the client side, you can tell Nix to use your binary cache using
The `nix-cache-info` file is a metadata file at the root of a [binary cache](@docroot@/package-management/binary-cache-substituter.md) (e.g., `https://cache.example.com/nix-cache-info`).
MIME type: `text/x-nix-cache-info`
## Format
Line-based key-value format:
```
Key: value
```
Leading and trailing whitespace is trimmed from values.
Lines without a colon are ignored.
Unknown keys are silently ignored.
## Fields
### `StoreDir`
The Nix store directory path that this cache was built for (e.g., `/nix/store`).
If present, Nix verifies that this matches the client's store directory:
```
error: binary cache 'https://example.com' is for Nix stores with prefix '/nix/store', not '/home/user/nix/store'
```
### `WantMassQuery`
`1` or `0`. Sets the default for [`want-mass-query`](@docroot@/store/types/http-binary-cache-store.md#store-http-binary-cache-store-want-mass-query).
### `Priority`
Integer. Sets the default for [`priority`](@docroot@/store/types/http-binary-cache-store.md#store-http-binary-cache-store-priority).
## Example
```
StoreDir: /nix/store
WantMassQuery: 1
Priority: 30
```
## Caching Behavior
Nix caches `nix-cache-info` in the [cache directory](@docroot@/command-ref/env-common.md#env-NIX_CACHE_HOME) with a 7-day TTL.
Nix32 is Nix's variant of base-32 encoding, used for [store path digests](@docroot@/protocols/store-path.md), hash output via [`nix hash`](@docroot@/command-ref/new-cli/nix3-hash.md), and the [`outputHash`](@docroot@/language/advanced-attributes.md#adv-attr-outputHash) derivation attribute.
## Alphabet
The Nix32 alphabet consists of these 32 characters:
```
0 1 2 3 4 5 6 7 8 9 a b c d f g h i j k l m n p q r s v w x y z
```
The letters `e`, `o`, `u`, and `t` are omitted.
## Byte Order
Nix32 encoding processes the hash bytes from the end (last byte first), while base-16 encoding processes from the beginning (first byte first).
Consequently, the string sort order is determined primarily by the first bytes for base-16, and by the last bytes for Nix32.
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