As far as I can tell, there's no real reason either of these need to
be 664. I'm willing to bet they were just a typo that has lasted for
7 years. While this shouldn't change anything, this is, IMHO, more
correct, so let's stop perpetuating the wrong mode!
We're not testing against these versions anymore.
If we bring that back (I would support that), we could do so in a clean
way, by making sure that the packaging we test against has a proper version
attribute.
Fix a footgun. In my case, I had a couple of build ("output")
directories sitting around.
rm -rf build-*
Was confused for a bit why a meson.build file was missing.
Probably also helps with autocompletion.
I tried meson-build-support first, but I had to add something like
a nix- prefix, in order to make meson happy. They've reserved the
meson- prefix.
I think I have failed to read the very long version-garbage-like
string for the second time now, leaving me oblivious to the crucial
info that a test failure happens in the context of an older daemon.
Before this change, expressions like:
with import <nixpkgs> {};
runCommand "foo" {} ''
echo '@nix {}' >&$NIX_LOG_FD
''
would result in Lix crashing, because accessing nonexistent fields of
a JSON object throws an exception.
Rather than handling each field individually, we just catch JSON
exceptions wholesale. Since these log messages are an unusual
circumstance, log a warning when this happens.
Fixes#544.
Change-Id: Idc2d8acf6e37046b3ec212f42e29269163dca893
(cherry picked from commit e55cd3beea710db727fd966f265a1b715b7285f3)
The Determinate Nix Installer has set nosuid and noatime in https://github.com/DeterminateSystems/nix-installer/pull/1338, and figured this perf and security improvement is worthy of upstreaming.
The /nix volume shouldn't have setuid binaries anyway, and filesystems seem to generally be noatime on macOS.
Further, the garbage collector doesn't use atime.
Instead of the unhelpful
warning: 'https://cache.flakehub.com' does not appear to be a binary cache
you now get
warning: unable to download 'https://cache.flakehub.com/nix-cache-info': HTTP error 401
response body:
{"code":401,"error":"Unauthorized","message":"Unauthorized."}
We *could* use a "native" manual instead - ie reusing a native
`nixpkgsFor.${buildPlatform}`, but this works, and also
works for possible cases where we have a custom or patched build tool.
Without the change `meson setup` fails on `Gentoo or Debian as those
don't use multicall binary:
$ meson setup ..
...
Executing subproject nix-functional-tests
...
../src/nix-functional-tests/meson.build:24:14: ERROR: Program 'coreutils' not found or not executable
The change always uses `ls` to look `coreutils` up.
Closes: https://github.com/NixOS/nix/issues/11975
Upstream `bzip2` does not provide `pkg-config` files. As a result an
attempt to build `nix` on some distributions like Gentoo failos the
configure as:
$ meson setup ..
...
Executing subproject perl
...
perl| Run-time dependency bzip2 found: NO (tried pkgconfig and cmake)
../src/perl/meson.build:68:12: ERROR: Dependency "bzip2" not found, tried pkgconfig and cmake
The change falls back to `bz2` library for such cases.
This prevents any potential cases of deletion through base pointer and its
non-virtual dtor, which might leak memory. Also gets rid of the warning:
/nix/store/fg7ass3a5m5pgl26qzfdniicbwbgzccy-gcc-13.2.0/include/c++/13.2.0/bits/stl_construct.h:88:2: warning: destructor called on non-final 'nix::flake::Settings' that has virtual functions but non-virtual destructor [-Wdelete-non-abstract-non-virtual-dtor]
88 | __location->~_Tp();
....
../src/libflake-c/nix_api_flake.cc:10:30: note: in instantiation of function template specialization 'nix::make_ref<nix::flake::Settings>' requested here
10 | auto settings = nix::make_ref<nix::flake::Settings>();
This gets rid of unnecessary copies in range-based-for loops and
local variables, when they are used solely as `const &`.
Also added a fixme comment about a suspicious move out of const,
which might not be intended.
This shuts up a 300-line warning that includes
/nix/store/fg7ass3a5m5pgl26qzfdniicbwbgzccy-gcc-13.2.0/include/c++/13.2.0/bits/stl_tree.h:182:25: warning: ‘*(std::_Rb_tree_header*)((char*)&<unnamed> + offsetof(nix::value_type, nix::DerivedPath::<unnamed>.std::variant<nix::DerivedPathOpaque, nix::DerivedPathBuilt>::<unnamed>.std::__detail::__variant::_Variant_base<nix::DerivedPathOpaque, nix::DerivedPathBuilt>::<unnamed>.std::__detail::__variant::_Move_assign_base<false, nix::DerivedPathOpaque, nix::DerivedPathBuilt>::<unnamed>.std::__detail::__variant::_Copy_assign_base<false, nix::DerivedPathOpaque, nix::DerivedPathBuilt>::<unnamed>.std::__detail::__variant::_Move_ctor_base<false, nix::DerivedPathOpaque, nix::DerivedPathBuilt>::<unnamed>.std::__detail::__variant::_Copy_ctor_base<false, nix::DerivedPathOpaque, nix::DerivedPathBuilt>::<unnamed>.std::__detail::__variant::_Variant_storage<false, nix::DerivedPathOpaque, nix::DerivedPathBuilt>::_M_u) + 24).std::_Rb_tree_header::_M_header.std::_Rb_tree_node_base::_M_parent’ may be used uninitialized [-Wmaybe-uninitialized]
182 | if (__x._M_header._M_parent != nullptr)
| ~~~~~~~~~~~~~~^~~~~~~~~
Since lib{expr,store,util}-test-support subprojects define nix_api_* helpers
for testing nix c bindings, they need to publicly depend on -c counterparts.
This makes their headers self-sufficient and does not rely on the -tests to add
necessary dependencies.
Get rid of this fixme. This does not appear to be used anywhere in
the nix codebase itself. Not sure why the comment mentioned C++20 erase
member function with predicate, but iterator-based algorithms are also fine.
Looks like some cruft has been left over from previous refactorings.
This removes dead variables, which should not have side effects in their
constructors. In cases where the variable initialization has a purpose
[[maybe_unused]] is inserted to silence compiler warnings.
* doc: Clarify that nix-shell still uses shell from host environment
* doc: Fix NIX_BUILD_SHELL description
* doc: Add anchor and link to NIX_BUILD_SHELL
* doc: Add example of default shell trickiness
Co-authored-by: Valentin Gagarin <valentin@gagarin.work>
This reduces the amount of boilerplate. More importantly, it provides
a place to add compiler flags (such as -O3) without having to add it
to every subproject (and the risk of forgetting to include it).
Fixes
nix: ../src/libexpr/primops/fetchTree.cc:37: void nix::emitTreeAttrs(EvalState&, const StorePath&, const fetchers::Input&, Value&, bool, bool): Assertion `narHash' failed.
on a lock file with an input that doesn't have a narHash. This can
happen when using a lock file created by the lazy-trees branch.
Cherry-picked from lazy-trees.
When diagnosing infinite recursion references to nullptr `Env` can be formed.
This happens only with `ExprBlackHole` is evaluated, which always leads to
`InfiniteRecursionError`.
UBSAN log for one such case:
```
../src/libexpr/eval-inline.hh:94:31: runtime error: reference binding to null pointer of type 'Env'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../src/libexpr/eval-inline.hh:94:31 in
```
First the motivation: I recently faced a bug that I assume is coming
from the topoSortPaths function where the GC was trying to delete a
path having some alive referrers. I resolved this by manually deleting
the faulty path referrers using nix-store --query --referrers. I sadly
did not manage to reproduce this bug.
This bug alone is not a big deal. However, this bug is
triggering a cascading failure: invalidatePathChecked is throwing a
PathInUse exception. This exception is not catched and fails the whole GC
run. From there, the machine (a builder machine) was unable to GC its
Nix store, which led to an almost full disk with no way to
automatically delete the dead Nix paths.
Instead, I think we should log the error for the specific store path
we're trying to delete, specifying we can't delete this path because
it still has referrers. Once we're done with logging that, the GC run
should continue to delete the dead store paths it can delete.
This is the first part of rewriteDerivation() factored out into its
own method. It's not used anywhere else at the moment, but it's useful
on lazy-trees for rewriting virtual paths.
It's not so common knowledge that forges also expose pull requests as
git refs. But it's actually a cool way of quickly testing someones
contribution, so I found it worth specifically mentioning it.
It seems that I copied the expression for baseDir thoughtlessly and
did not come back to it.
- `baseDir` was only used in the `fromArgs` branch.
- `fromArgs` is true when `packages` is true.
This interferes with the progress bar, resulting in output like
evaluating derivation 'git+file:///home/eelco/Dev/nix-master#packages.x86_64-linux.default'/nix/store/zz8v96j5md952x0mxfix12xqnvq5qv5x-nix-2.26.0pre20241114_a95f6ea.drv
This patch gets rid of UB when verbosity exceeds the maximum logging value of `lvlVomit = 7` and
reaches invalid values (e.g. 8). This is actually triggered in functional tests.
There are too many occurrences to list, but here's one from the UBSAN log:
../src/libstore/gc.cc:610:5: runtime error: load of value 8, which is not a valid value for type 'Verbosity'
This was first tagged as 2.15.0, 1½ years ago; plenty of time for
everyone to catch up.
By now, the warning is causing more confusion than that it is helpful,
because passing a `.drv` or `drvPath` has legitimate use cases.
The API docs build is extremely noisy (#11841) and probably not many
people care about it anyway. Also, they get rebuild on *every* ninja
invocation which is generally a waste of time.
Of course, you can still build the docs via `nix build
.#nix-{internal,external}-api-docs`, which is pretty fast.
The new package output attributes are somewhat experimental, and
provided for compatibility most of all.
We'll see how well this goes before the changes proposed in
https://github.com/NixOS/nix/issues/6507
Add options uid, gid, uname, and gname to docker.nix.
Setting these to e.g. 1000, 1000, "user", "user" will build an image
which runs and allows using Nix as that user.
In these trivial cases the final vector size (or lower bound on the size) is known,
so we can avoid some vector reallocations. This is not very important, but is just
good practice and general hygiene.
This is good practice to avoid pessimisations.
Left comments for the reasoning why ctors should be noexcept.
There are some tricky cases where we intentionally want throwing move ctors/assignments.
But those cases should really be reviewed, since some of those can be replaced
with more idiomatic copy/move-and-swap.
`auto &&` and `T &&` are forwarding references and can be
either lvalue or rvalue references. Moving from universal references
is incorrect and should not be done.
Moving from integral or floating-point values is pointless and just
worsens debug performance.
Naming class member variables the same as constructor arguments is a very
slippery slope because of how member variable names get resolved. Compiler
is not very helpful here and we need static analysis to forbid this kind of
stuff.
The following example illustrates the cause quite well:
```cpp
struct B {
B(int) {}
};
struct A {
A(int b): b([&](){
return b;
static_assert(std::is_same_v<decltype(b), int>);
}()) {
static_assert(std::is_same_v<decltype(b), int>);
}
void member() {
static_assert(std::is_same_v<decltype(b), B>);
}
B b;
};
int main() {
A(1).member();
}
```
From N4861 6.5.1 Unqualified name lookup:
> In all the cases listed in [basic.lookup.unqual], the scopes are searched
> for a declaration in the order listed in each of the respective categories;
> name lookup ends as soon as a declaration is found for the name.
> If no declaration is found, the program is ill-formed.
In the affected code there was a use-after-move for all accesses in the constructor
body, but this UB wasn't triggered.
These types of errors are trivial to catch via clang-tidy's [clang-analyzer-cplusplus.Move].
This was broken since a03bb4455c because
Nix 2.18 does not support broken $SHELL settings. So don't try a
broken $SHELL on old Nix versions. (It's a mystery though why
tests.remoteBuilds_local_nix_2_13 and tests.remoteBuilds_local_nix_2_3
didn't fail...)
https://hydra.nixos.org/build/277366807
This may occur when stderr is a tty but stdin is empty.
E.g.
$ nix build </dev/null
error: unexpected EOF reading a line
These stdio handles are how some non-interactive sandboxes behave,
including the Nix build sandbox and Hercules CI Effects.
Unfortunately `StringSource` class is very easy was very easy to misuse
because the ctor took a plain `std::string_view` which has a bad habit
of being implicitly convertible from an rvalue `std::string`. This lead
to unintentional use-after-free bugs.
This patch makes `StringSource` much harder to misuse by disabling the ctor
from a `std::string &&` (but `const std::string &` is ok).
Fix affected tests from libstore-tests.
Reformat those tests with clangd's range formatting since the diff is tiny
and it seems appropriate.
It had gotten rather big. Hopefully we'll eventually have some generic
infra for a "multi-package dev shell" and not need so much code for
this, but until then it's better in a separate file.
operators are an everyday thing in the Nix language, and this page will
hopefully be consulted by many users.
string contexts are quite exotic, and not linking to the detailed
explanation will require readers to figure out manually what this is
about, or worse, skim over and run into problems later.
* doc/manual: Add 'Debugging Nix' section
This commit adds a new 'Debugging Nix' section to the Nix manual. It provides instructions on how to build Nix with debug symbols and how to debug the Nix binary using debuggers like `lldb`.
Co-authored-by: Jörg Thalheim <Mic92@users.noreply.github.com>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
We now just check that the fetcher doesn't change any attributes in
the input, and return all the original attributes (i.e. discarding any
new attributes and keeping any attributes that the fetcher didn't
keep).
This fixes the error
'{"__final":true,"lastModified":1686592866,"narHash":"sha256-riGg89eWhXJcPNrQGcSwTEEm7CGxWC06oSX44hajeMw","owner":"nixos","repo":"nixpkgs","rev":"0eeebd64de89e4163f4d3cf34ffe925a5cf67a05","type":"github"}' resulted in different input
'{"__final":true,"lastModified":1686592866,"narHash":"sha256-riGg89eWhXJcPNrQGcSwTEEm7CGxWC06oSX44hajeMw=","owner":"nixos","repo":"nixpkgs","rev":"0eeebd64de89e4163f4d3cf34ffe925a5cf67a05","type":"github"}'
in flake-regressions/tests/nix-community/patsh/0.2.1 (note the lack of
a trailing '=' in the NAR hash in the lock file).
OpenBSD doesn't support `lutimes`, but does support `utimensat` which
subsumes it. In fact, all the BSDs, Linux, and newer macOS all support
it. So lets make this our first choice for the implementation.
In addition, let's get rid of the `lutimes` `ENOSYS` special case. The
Linux manpage says
> ENOSYS
>
> The kernel does not support this call; Linux 2.6.22 or later is
> required.
which I think is the origin of this check, but that's a very old version
of Linux at this point. The code can be simplified a lot of we drop
support for it here (as we've done elsewhere, anyways).
Co-Authored-By: John Ericson <John.Ericson@Obsidian.Systems>
Backward-compatible schema changes (e.g. those that add tables or
nullable columns) now no longer need a change to the global schema
file (/nix/var/nix/db/schema). Thus, old Nix versions can continue to
access the database.
This is especially useful for schema changes required by experimental
features. In particular, it replaces the ad-hoc handling of the schema
changes for CA derivations (i.e. the file /nix/var/nix/db/ca-schema).
Schema versions 8 and 10 could have been handled by this mechanism in
a backward-compatible way as well.
OpenBSD dynamic libraries never link to libc directly.
Instead, they have undefined symbols for all libc functions they use
that ld.so resolves to the libc referred to in the main executable.
Thus, disallowing undefined symbols will always fail
the default int64_t max was still overflowing for me, when this was dumped as json (noticed during building the manual).
So making 0, the default and define it as "no warnings" fixes the situtation.
Also it's much more human-readable in documentation.
This works because the `builder` and `args` variables are only used
in the non-builtin code path.
Co-Authored-By: Théophane Hufschmitt <theophane.hufschmitt@tweag.io>
tests/functional/help.sh calls nix-* commands with option --help
if nix is built without documentation the option --help throws an error
because the man page it wants to display is missing
This overall seems like insecure tmp file handling to me. Because other
users could replace files in /tmp with a symlink and make the nix-shell
override other files.
fixes https://github.com/NixOS/nix/issues/11470
Introduced in 8f6b347abd without explanation.
Throwing anything that's not that is a programming mistake that we don't want
to ignore silently. A crash would be ok, because that means we/they can fix
the offending throw.
Otherwise, if checkInterrupt() in any of the supported store operations
would catch onto a user interrupt, the exception would bubble to the thread
start and be handled by std::terminate(): a crash.
We haven't added the narHash attribute yet at that point. And if the
caller uses getAccesor() instead of fetchToStore() (e.g. in `nix
registry pin`), the narHash attribute will never be added. This could
lead to a mismatch.
The ability to substitute inputs was removed in #10612 because it was
broken: with user-specified inputs containing a `narHash` attribute,
substitution resulted in an input that lacked the attributes returned
by the real fetcher (such as `lastModified`).
To fix this, we introduce a new input attribute `final`. If `final =
true`, fetching the input cannot add or change any attributes.
We only attempt to substitute inputs that have `final = true`. This is
implied by lock file entries; we only write a lock file if all its
entries are "final".
The user can specified `final = true` in `fetchTree`, in which case it
is their responsibility to ensure that all attributes returned by the
fetcher are included in the `fetchTree` call. For example,
nix eval --impure --expr 'builtins.fetchTree { type = "github"; owner = "NixOS"; repo = "patchelf"; final = true; narHash = "sha256-FSoxTcRZMGHNJh8dNtKOkcUtjhmhU6yQXcZZfUPLhQM="; }'
succeeds in a store path with the specified NAR hash exists or is
substitutable, but fails with
error: fetching final input '{"final":true,"narHash":"sha256-FSoxTcRZMGHNJh8dNtKOkcUtjhmhU6yQXcZZfUPLhQM=","owner":"NixOS","repo":"patchelf","type":"github"}' resulted in different input '{"final":true,"lastModified":1718457448,"narHash":"sha256-FSoxTcRZMGHNJh8dNtKOkcUtjhmhU6yQXcZZfUPLhQM=","owner":"NixOS","repo":"patchelf","rev":"a0f54334df36770b335c051e540ba40afcbf8378","type":"github"}'
... and remove a few unused arguments.
This adds pkg-config to a two or three packages that don't use it,
but we shouldn't let that bother us. It's like our personal stdenv.
If you have the Nix store mounted from a nonlocal filesystem whose
exporter is not running as root, making the directory mode 000 makes it
inaccessible to that remote unprivileged user and therefore breaks the
build. (Specifically, I am running into this with a virtiofs mount using
Apple Virtualization.framework as a non-root user, but I expect the
same thing would happen with virtiofs in qemu on Linux as a non-root
user or with various userspace network file servers.)
Make the directory mode 500 (dr-x------) to make the sandbox work in
this use case, which explicitly conveys our intention to read and search
the directory. The code only works because root can already bypass
directory checks, so this does not actually grant more permissions to
the directory owner / does not make the sandbox less secure.
This allows `nix copy` to atomically copy a store path and point a
profile to it, without the risk that the store path might be GC'ed in
between. This is useful for instance when deploying a new NixOS system
profile from a remote store.
Using '-L' caused another call to setLogFormat(), which caused another
ProgressBar to be created. But the ProgressBar should be a singleton.
To do: remove LogFormat::barWithLogs. '-L' should be a setting of the
ProgressBar, not a different log format.
[test "$ENABLE_BUILD" == "no" && test "$ENABLE_UNIT_TESTS" == "yes"],
[AC_MSG_ERROR([Cannot enable unit tests when building overall is disabled. Please do not pass '--enable-unit-tests' or do not pass '--disable-build'.])])
AC_ARG_ENABLE(functional-tests, AS_HELP_STRING([--disable-functional-tests],[Do not build the tests]),
[test "$ENABLE_BUILD" == "no" && test "$ENABLE_DOC_GEN" == "yes"],
[AC_MSG_ERROR([Cannot enable generated docs when building overall is disabled. Please do not pass '--enable-doc-gen' or do not pass '--disable-build'.])])
AS_IF(
[test "$ENABLE_FUNCTIONAL_TESTS" == "yes" || test "$ENABLE_DOC_GEN" == "yes"],
[NEED_PROG(jq, jq)])
AS_IF([test "$ENABLE_BUILD" == "yes"],[
# Look for boost, a required dependency.
# Note that AX_BOOST_BASE only exports *CPP* BOOST_CPPFLAGS, no CXX flags,
# and CPPFLAGS are not passed to the C++ compiler automatically.
# Thus we append the returned CPPFLAGS to the CXXFLAGS here.
AS_HELP_STRING([--disable-cpuid], [Do not determine microarchitecture levels with libcpuid (relevant to x86_64 only)]))
if test "x$enable_cpuid" != "xno"; then
PKG_CHECK_MODULES([LIBCPUID], [libcpuid],
[CXXFLAGS="$LIBCPUID_CFLAGS $CXXFLAGS"
have_libcpuid=1
AC_DEFINE([HAVE_LIBCPUID], [1], [Use libcpuid])]
)
fi
fi
AC_SUBST(HAVE_LIBCPUID, [$have_libcpuid])
# Look for libseccomp, required for Linux sandboxing.
case "$host_os" in
linux*)
AC_ARG_ENABLE([seccomp-sandboxing],
AS_HELP_STRING([--disable-seccomp-sandboxing],[Don't build support for seccomp sandboxing (only recommended if your arch doesn't support libseccomp yet!)
]))
if test "x$enable_seccomp_sandboxing" != "xno"; then
synopsis: Use envvars NIX_CACHE_HOME, NIX_CONFIG_HOME, NIX_DATA_HOME, NIX_STATE_HOME if defined
prs: [11351]
---
Added new environment variables:
-`NIX_CACHE_HOME`
-`NIX_CONFIG_HOME`
-`NIX_DATA_HOME`
-`NIX_STATE_HOME`
Each, if defined, takes precedence over the corresponding [XDG environment variable](@docroot@/command-ref/env-common.md#xdg-base-directories).
This provides more fine-grained control over where Nix looks for files, and allows to have a stand-alone Nix environment, which only uses files in a specific directory, and doesn't interfere with the user environment.
synopsis: Define integer overflow in the Nix language as an error
issues: [10968]
prs: [11188]
---
Previously, integer overflow in the Nix language invoked C++ level signed overflow, which was undefined behaviour, but *usually* manifested as wrapping around on overflow.
Since prior to the public release of Lix, Lix had C++ signed overflow defined to crash the process and nobody noticed this having accidentally removed overflow from the Nix language for three months until it was caught by fiddling around.
Given the significant body of actual Nix code that has been evaluated by Lix in that time, it does not appear that nixpkgs or much of importance depends on integer overflow, so it appears safe to turn into an error.
Some other overflows were fixed:
-`builtins.fromJSON` of values greater than the maximum representable value in a signed 64-bit integer will generate an error.
-`nixConfig` in flakes will no longer accept negative values for configuration options.
Integer overflow now looks like the following:
```
$ nix eval --expr '9223372036854775807 + 1'
error: integer overflow in adding 9223372036854775807 + 1
The `build-hook` setting's default is less useful when using `libnixstore` as a library
prs:
- 11178
---
*This is an obscure issue that only affects usage of the `libnixstore` library outside of the Nix executable.*
As part the ongoing [rewrite of the build system](https://github.com/NixOS/nix/issues/2503) to use [Meson](https://mesonbuild.com/), we are also switching to packaging individual Nix components separately (and building them in separate derivations).
This means that when building `libnixstore` we do not know where the Nix binaries will be installed --- `libnixstore` doesn't know about downstream consumers like the Nix binaries at all.
*This is also unrelated to the _`post`_-`build-hook`*, which is often used for pushing to a cache.*
This has a small adverse affect on remote building --- the `build-remote` executable that is specified from the [`build-hook`](@docroot@/command-ref/conf-file.md#conf-build-hook) setting will not be gotten from the (presumed) installation location, but instead looked up on the `PATH`.
This means that other applications linking `libnixstore` that wish to use remote building must arrange for the `nix` command to be on the PATH (or manually overriding `build-hook`) in order for that to work.
Long term we don't envision this being a downside, because we plan to [get rid of `build-remote` and the build hook setting entirely](https://github.com/NixOS/nix/issues/1221).
There should simply be no need to have an extra, intermediate layer of remote-procedure-calling when we want to connect to a remote builder.
The build hook protocol did in principle support custom ways of remote building, but that can also be accomplished with a custom service for the ssh or daemon/ssh-ng protocols, or with a custom [store type](@docroot@/store/types/index.md) i.e. `Store` subclass. <!-- we normally don't mention classes, but consider that this release note is about a library use case -->
The Perl bindings no longer expose `getBinDir` either, since the underlying C++ libraries those bindings wrap no longer know the location of installed binaries as described above.
synopsis: wrap filesystem exceptions more correctly
issues: []
prs: [11378]
---
With the switch to `std::filesystem` in different places, Nix started to throw `std::filesystem::filesystem_error` in many places instead of its own exceptions.
This lead to no longer generating error traces, for example when listing a non-existing directory, and can also lead to crashes inside the Nix REPL.
This version catches these types of exception correctly and wrap them into Nix's own exeception type.
Nix now has a setting `fsync-store-paths` that ensures that new store paths are durably written to disk before they are registered as "valid" in Nix's database. This can prevent Nix store corruption if the system crashes or there is a power loss. This setting defaults to `false`.
The advantage is that this avoids a time window where *path* is not a garbage collector root, and so could be deleted by a concurrent `nix store gc` process.
synopsis: Show package descriptions with `nix flake show`
issues: [10977]
prs: [10980]
---
`nix flake show` will now display a package's `meta.description` if it exists. If the description does not fit in the terminal it will be truncated to fit the terminal width. If the size of the terminal width is unknown the description will be capped at 80 characters.
Nix will no longer attempt to substitute the source code of flakes from a binary cache. This functionality was broken because it could lead to different evaluation results depending on whether the flake was available in the binary cache, or even depending on whether the flake was already in the local store.
Previously `<nix/fetchurl.nix>` did not do TLS verification. This was because the Nix sandbox in the past did not have access to TLS certificates, and Nix checks the hash of the fetched file anyway. However, this can expose authentication data from `netrc` and URLs to man-in-the-middle attackers. In addition, Nix now in some cases (such as when using impure derivations) does *not* check the hash. Therefore we have now enabled TLS verification. This means that downloads by `<nix/fetchurl.nix>` will now fail if you're fetching from a HTTPS server that does not have a valid certificate.
`<nix/fetchurl.nix>` is also known as the builtin derivation builder `builtin:fetchurl`. It's not to be confused with the evaluation-time function `builtins.fetchurl`, which was not affected by this issue.
A local Nix installation can forward Nix builds to other machines,
this allows multiple builds to be performed in parallel.
Remote builds also allow Nix to perform multi-platform builds in a
semi-transparent way. For example, if you perform a build for a
`x86_64-darwin` on an `i686-linux` machine, Nix can automatically
forward the build to a `x86_64-darwin` machine, if one is available.
## Requirements
For a local machine to forward a build to a remote machine, the remote machine must:
- Have Nix installed
- Be running an SSH server, e.g. `sshd`
- Be accessible via SSH from the local machine over the network
- Have the local machine's public SSH key in `/etc/ssh/authorized_keys.d/<username>`
- Have the username of the SSH user in the `trusted-users` setting in `nix.conf`
## Testing
To test connecting to a remote Nix instance (in this case `mac`), run:
```console
nix store info --store ssh://username@mac
```
To specify an SSH identity file as part of the remote store URI add a
query paramater, e.g.
```console
nix store info --store ssh://username@mac?ssh-key=/home/alice/my-key
```
Since builds should be non-interactive, the key should not have a
passphrase. Alternatively, you can load identities ahead of time into
`ssh-agent` or `gpg-agent`.
In a multi-user installation (default), builds are executed by the Nix
Daemon. The Nix Daemon cannot prompt for a passphrase via the terminal
or `ssh-agent`, so the SSH key must not have a passphrase.
In addition, the Nix Daemon's user (typically root) needs to have SSH
access to the remote builder.
Access can be verified by running `sudo su`, and then validating SSH
access, e.g. by running `ssh mac`. SSH identity files for root users
are usually stored in `/root/.ssh/` (Linux) or `/var/root/.ssh` (MacOS).
If you get the error
```console
bash: nix: command not found
error: cannot connect to 'mac'
```
then you need to ensure that the `PATH` of non-interactive login shells
contains Nix.
The [list of remote build machines](@docroot@/command-ref/conf-file.md#conf-builders) can be specified on the command line or in the Nix configuration file.
For example, the following command allows you to build a derivation for `x86_64-darwin` on a Linux machine:
The [URL to the Nix store](@docroot@/store/types/index.md#store-url-format) to use for evaluation, i.e. where to store derivations (`.drv` files) and inputs referenced by them.
Interpret the command line arguments as a list of Nix expressions to be parsed and evaluated, rather than as a list of file names of Nix expressions.
@@ -194,6 +210,10 @@ Most Nix commands accept the following command-line options:
Paths added through `-I` take precedence over the [`nix-path` configuration setting](@docroot@/command-ref/conf-file.md#conf-nix-path) and the [`NIX_PATH` environment variable](@docroot@/command-ref/env-common.md#env-NIX_PATH).
Set the Nix configuration option *name* to *value*.
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