Avoid needless work and throwing away invariants.
These conversions date back to when `StorePath` was in Rust and there
were issues with it missing utility methods.
Previously, getDefaultNixPath was called too early: at initialisation
time, before CLI and config have been processed, when `restrictEval` and
`pureEval` both have their default value `false`. Call it when
initialising the EvalState instead, and use `setDefault`.
clangStdenv compiles with a single warning:
```
warning: destructor called on non-final 'nix::PosAdapter' that has virtual functions but non-virtual destructor [-Wdelete-non-abstract-non-virtual-dtor]
```
This fixes the warning by making the destructor of PosAdapter virtual,
deffering to the correct destructor from the concrete child classes.
This has no impact in the end, as none of these classes have specific
destructors.
Technicaly, it may be faster not to have this indirection, but as per
the warning, there is only one place where we have to delete abstract
PosAdapter values.
Not worth bikesheding I guess.
Allows checking directory entry type of a single file/directory.
This was added to optimize the use of `builtins.readDir` on some
filesystems and operating systems which cannot detect this information
using POSIX's `readdir`.
Previously `builtins.readDir` would eagerly use system calls to lookup
these filetypes using other interfaces; this change makes these
operations lazy in the attribute values for each file with application
of `builtins.readFileType`.
We had some local variables left over from the older (more
complicated) implementation of this function. They should all be unused,
but one wasn't by mistake.
Delete them all, and replace the one that was still in use as intended.
It's used as the “system” profile in a bunch of places, so better not
touch it. Besides, it doesn't hurt to keep it since it's owned by root
any way, so it doesn't have the `chown` problem that the user profiles
had and that led to wanting to move them on the client-side.
Rather than using `/nix/var/nix/{profiles,gcroots}/per-user/`, put the user
profiles and gcroots under `$XDG_DATA_DIR/nix/{profiles,gcroots}`.
This means that the daemon no longer needs to manage these paths itself
(they are fully handled client-side). In particular, it doesn’t have to
`chown` them anymore (removing one need for root).
This does change the layout of the gc-roots created by nix-env, and is
likely to break some stuff, so I’m not sure how to properly handle that.
Originally there was no `path-info.*`, then there was `path-info.hh`,
then there was `path-info.cc`, but only for new things. Moving this
stuff over makes everything consistent.
Instead of needing to run `nix show-config --json | jq -r
'."warn-dirty".value'` to view the value of `warn-dirty`, you can now
run `nix show-config warn-dirty`.
This should be a non-empty set, and so we don't want people doing this
by accident. We remove the zero-0 constructor with a little inheritance
trickery.
`DerivedPath::Built` and `DerivationGoal` were previously using a
regular set with the convention that the empty set means all outputs.
But it is easy to forget about this rule when processing those sets.
Using `OutputSpec` forces us to get it right.
It appears that on current macOS versions, our use of poll() to detect
client disconnects no longer works. As a workaround, poll() for
POLLRDNORM, since this *will* wake up when the client has
disconnected. The downside is that it also wakes up when input is
available. So just sleep for a bit in that case. This means that on
macOS, a client disconnect may take up to a second to be detected,
but that's better than not being detected at all.
Fixes#7584.
This way the links are clearly within the manual (ie not absolute paths),
while allowing snippets to reference the documentation root reliably,
regardless of at which base url they're included.
Prior to this change, we had a bunch of ad-hoc string manipulation code
scattered around. This made it hard to figure out what data model for
string contexts is.
Now, we still store string contexts most of the time as encoded strings
--- I was wary of the performance implications of changing that --- but
whenever we parse them we do so only through the
`NixStringContextElem::parse` method, which handles all cases. This
creates a data type that is very similar to `DerivedPath` but:
- Represents the funky `=<drvpath>` case as properly distinct from the
others.
- Only encodes a single output, no wildcards and no set, for the
"built" case.
(I would like to deprecate `=<path>`, after which we are in spitting
distance of `DerivedPath` and could maybe get away with fewer types, but
that is another topic for another day.)
macOS doesn't have user namespacing, so the gid of the builder needs
to be nixbld. The logic got "has sandboxing enabled" confused with
"has user namespaces".
Fixes#7529.
This basically reverts 6e5165b773.
It fixes errors like
sandbox-exec: <internal init prelude>:292:47: unable to open sandbox-minimal.sb: not found
when trying to run a development Nix installed in a user's home
directory.
Also, we're trying to minimize the number of installed files
to make it possible to deploy Nix as a single statically-linked
binary.
Adds a new boolean structured attribute
`outputChecks.<output>.unsafeDiscardReferences` which disables scanning
an output for runtime references.
__structuredAttrs = true;
outputChecks.out.unsafeDiscardReferences = true;
This is useful when creating filesystem images containing their own embedded Nix
store: they are self-contained blobs of data with no runtime dependencies.
Setting this attribute requires the experimental feature
`discard-references` to be enabled.
Previously addTempRoot() acquired the LocalStore state lock and waited
for the garbage collector to reply. If the garbage collector is in the
same process (as it the case with auto-GC), this would deadlock as
soon as the garbage collector thread needs the LocalStore state lock.
So now addTempRoot() uses separate Syncs for the state that it
needs. As long at the auto-GC thread doesn't call addTempRoot() (which
it shouldn't), it shouldn't deadlock.
Fixes#3224.
This also moves the file handle into its own Sync object so we're not
holding the _state while acquiring the file lock. There was no real
deadlock risk here since locking a newly created file cannot block,
but it's still a bit nicer.
This has the same goal as b13fd4c58e81b2b2b0d72caa5ce80de861622610,but
achieves it in a different way in order to not break
`nix why-depends --derivation`.
In principle, this should avoid deadlocks where two instances of Nix are
holding a shared lock on big-lock and are both waiting to get an
exclusive lock.
However, it seems like `flock(2)` is supposed to do this automatically,
so it's not clear whether this is actually where the problem comes from.
This makes 'nix develop' set the Linux personality in the same way
that the actual build does, allowing a command like 'nix develop
nix#devShells.i686-linux.default' on x86_64-linux to work correctly.
Without this, the error is lost, and it makes for a hard to debug
situation. Also remove some of the busyness inside the sqlite_open_v2
args.
The errcode returned is not the extended one. The only way to make open
return an extended code, would be to add SQLITE_OPEN_EXRESCODE to the
flags. In the future it might be worth making this change,
which would also simplify the existing SQLiteError code.
This makes 'nix build' work on paths (which will be copied to the
store) and store paths (returned as is). E.g. the following flake
output attributes can be built using 'nix build .#foo':
foo = ./src;
foo = self.outPath;
foo = builtins.fetchTarball { ... };
foo = (builtins.fetchTree { .. }).outPath;
foo = builtins.fetchTree { .. } + "/README.md";
foo = builtins.storePath /nix/store/...;
Note that this is potentially risky, e.g.
foo = /.;
will cause Nix to try to copy the entire file system to the store.
What doesn't work yet:
foo = self;
foo = builtins.fetchTree { .. };
because we don't handle attrsets with an outPath attribute in it yet,
and
foo = builtins.storePath /nix/store/.../README.md;
since result symlinks have to point to a store path currently (rather
than a file inside a store path).
Fixes#7417.
They did not include the detailed error message, losing essential
information for troubleshooting.
Example message:
warning: creating statement 'insert or rplace into NARs(cache, hashPart, namePart, url, compression, fileHash, fileSize, narHash, narSize, refs, deriver, sigs, ca, timestamp, present) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, 1)': at offset 10: SQL logic error, near "rplace": syntax error (in '/tmp/nix-shell.grQ6f7/nix-test/tests/binary-cache/test-home/.cache/nix/binary-cache-v6.sqlite')
It's not the best example; more important information will be in
the message for e.g. a constraint violation.
I don't see why this specific error is printed as a warning, but
that's for another commit.
Unsetting `build-users-group` (without `auto-allocate-uids` enabled)
gives the following error:
```
src/libstore/lock.cc:25: static std::unique_ptr<nix::UserLock> nix::SimpleUserLock::acquire(): Assertion `settings.buildUsersGroup != ""' failed.
```
Fix the logic in `useBuildUsers` and document the default value
for `build-users-group`.
This makes the position object used in exceptions abstract, with a
method getSource() to get the source code of the file in which the
error originated. This is needed for lazy trees because source files
don't necessarily exist in the filesystem, and we don't want to make
libutil depend on the InputAccessor type in libfetcher.
Make everything be in the form "while ..." (most things were already),
and in particular *don't* use other propositions that must go after or
before specific "while ..." clauses to make sense.
When debugging nix expressions the outermost trace tends to be more useful
than the innermost. It is therefore printed last to save developers from
scrolling.
We used to set enforceDeterminism to true in the settings (by default)
and thus did send a non-zero value over the wire. The value should
probably be ignored as it should only matter if nrRounds is non-zero
as well.
Having the old code here where the value is expected to be zero only
works with the same version of Nix where we are sending zero. We
should always test this against older Nix versions being client or
server as otherwise upgrade in larger networks might be a pain.
Fixes 8e0946e8df
Fix#6209
When trying to run `nix log <installable>`, try first to resolve the derivation pointed to
by `<installable>` as it is the resolved one that holds the build log.
This has a couple of shortcomings:
1. It’s expensive as it requires re-reading the derivation
2. It’s brittle because if the derivation doesn’t exist anymore or can’t
be resolved (which is the case if any one of its build inputs is missing),
then we can’t access the log anymore
However, I don’t think we can do better (at least not right now).
The alternatives I see are:
1. Copy the build log for the un-resolved derivation. But that means a
lot of duplication
2. Store the results of the resolving in the db. Which might be the best
long-term solution, but leads to a whole new class of potential
issues.
These only functioned if a very narrow combination of conditions held:
- The result path does not yet exist (--check did not result in
repeated builds), AND
- The result path is not available from any configured substituters, AND
- No remote builders that can build the path are available.
If any of these do not hold, a derivation would be built 0 or 1 times
regardless of the repeat option. Thus, remove it to avoid confusion.
The old way was not correct.
Here is an example:
```
$ nix-instantiate --eval --expr 'let x = a: throw "asdf"; in x 1' --show-trace
error: asdf
… while evaluating 'x'
at «string»:1:9:
1| let x = a: throw "asdf"; in x 1
| ^
… from call site
at «string»:1:29:
1| let x = a: throw "asdf"; in x 1
| ^
```
and yet also:
```
$ nix-instantiate --eval --expr 'let x = a: throw "asdf"; in x' --show-trace
<LAMBDA>
```
Here is the thing: in both cases we are evaluating `x`!
Nix is a higher-order languages, and functions are a sort of value. When
we write `x = a: ...`, `a: ...` is the expression that `x` is being
defined to be, and that is already a value. Therefore, we should *never*
get an trace that says "while evaluating `x`", because evaluating `a:
...` is *trival* and nothing happens during it!
What is actually happening here is we are applying `x` and evaluating
its *body* with arguments substituted for parameters. I think the
simplest way to say is just "while *calling* `x`", and so that is what I
changed it to.
We need to close the GC server socket before shutting down the active
GC client connections, otherwise a client may (re)connect and get
ECONNRESET. But also handle ECONNRESET for resilience.
Fixes random failures like
GC socket disconnected
connecting to '/tmp/nix-shell.y07M0H/nix-test/default/var/nix/gc-socket/socket'
sending GC root '/tmp/nix-shell.y07M0H/nix-test/default/store/kb5yzija0f1x5xkqkgclrdzldxj6nnc6-non-blocking'
reading GC root from client: error: unexpected EOF reading a line
1 store paths deleted, 0.00 MiB freed
error: reading from file: Connection reset by peer
in gc-non-blocking.sh.
It calls strlen() on the input (rather than simply copying at most
`size` bytes), which can fail if the input is not zero-terminated and
is inefficient in any case.
Fixes#7347.
why-depends assumed that we knew the output path of the second argument.
For CA derivations, we might not know until it's built. One way to solve
this would be to build the second installable to get the output path.
In this case we don't need to, though. If the first installable (A)
depends on the second (B), then getting the store path of A will
necessitate having the store path B. The contrapositive is, if the store
path of B is not known (i.e. it's a CA derivation which hasn't been
built), then A does not depend on B.
We shouldn't skip this if the supplementary group list is empty,
because then the sandbox won't drop the supplementary groups of the
parent (like "root").
The new experimental feature 'cgroups' enables the use of cgroups for
all builds. This allows better containment and enables setting
resource limits and getting some build stats.
It occurred when a output of the dependency was already available,
so it didn't need rebuilding and didn't get added to the
inputDrvOutputs.
This process-related info wasn't suitable for the purpose of finding
the actual input paths for the builder. It is better to do this in
absolute terms by querying the store.
This change is needed to support aws-sdk-cpp 1.10 and newer.
I opted not to make this dependent on the sdk version because
the crt dependency has been in the interface of the older
sdk as well, and it was only coincidence that libstore didn't
make use of any privately defined symbols directly.
When calling `builtins.readFile` on a store path, the references of that
path are currently added to the resulting string's context.
This change makes those references the *possible* context of the string,
but filters them to keep only the references whose hash actually appears
in the string, similarly to what is done for determining the runtime
references of a path.
Cgroups are now only used for derivations that require the uid-range
range feature. This allows auto UID allocation even on systems that
don't have cgroups (like macOS).
Also, make things work on modern systems that use cgroups v2 (where
there is a single hierarchy and no "systemd" controller).
after discussing this with multiple people, I'm convinced that "build
task" is more precise: a derivation is not an action, but inert until it
is built. also it's easier to pronounce.
proposal: use "build task" for the generic concept "description of how
to derive new files from the contents of existing files". then it will
be easier to distinguish what we mean by "derivation" (a specific data
structure and Nix language value type) and "store derivation" (a
serialisation of a derivation into a file in the Nix store).
readline is not re-entrant, so entering the debugger from the
completioncallback results in an eventual segfault.
The workaround is to temporarily disable the debugger when searching
for possible completions.
Call it as `['nix', '__build-remote', ... ]` rather than the previous
`["__build-remote", "nix __build-remote", ... ]` which seemed to have
been most likely unintended
The description of the --profile option talks about the "update" operation.
This is probably meant for operations such as "nix profile install", but the
same option is reused in other subcommands, which do not update the profile,
such as "nix profile {list,history,diff-closures}".
We update the description to make sense in both contexts.
Currently, Nix passes `-a` when it runs commands on a remote machine via
SSH, which disables agent forwarding. This causes issues when the
`ForwardAgent` option is set in SSH config files, as the command line
operation always overrides those.
In particular, this causes issues if the command being run is `sudo`
and the remote machine is configured with the equivalent of NixOS's
`security.pam.enableSSHAgentAuth` option. Not allowing SSH agent
forwarding can cause authentication to fail unexpectedly.
This can currently be worked around by setting `NIX_SSHOPTS="-A"`, but
we should defer to the options in the SSH config files to be least
surprising for users.
* Clarify the documentation of foldl': That the arguments are forced
before application (?) of `op` is necessarily true. What is important
to stress is that we force every application of `op`, even when the
value turns out to be unused.
* Move the example before the comment about strictness to make it less
confusing: It is a general example and doesn't really showcase anything
about foldl' strictness.
* Add test cases which nail down aspects of foldl' strictness:
* The initial accumulator value is not forced unconditionally.
* Applications of op are forced.
* The list elements are not forced unconditionally.
After we've send "\2\n" to the parent, we can't send a serialized
exception anymore. It will show up garbled like
$ nix-build --store /tmp/nix --expr 'derivation { name = "foo"; system = "x86_64-linux"; builder = "/foo/bar"; }'
this derivation will be built:
/nix/store/xmdip0z5x1zqpp6gnxld3vqng7zbpapp-foo.drv
building '/nix/store/xmdip0z5x1zqpp6gnxld3vqng7zbpapp-foo.drv'...
ErrorErrorEexecuting '/foo/bar': No such file or directory
error: builder for '/nix/store/xmdip0z5x1zqpp6gnxld3vqng7zbpapp-foo.drv' failed with exit code 1
While trying to use an alternate directory for my Nix installation, I
noticed that nix's output didn't reflect the updated state
directory. This patch corrects that and now prints the warning before
attempting to create the directory (if the directory creation fails,
it wouldn't have been obvious why nix was attempting to create the
directory in the first place).
With this patch, I now get the following warning:
warning: '/home/deck/.var/app/org.nixos.nix/var/nix' does not
exist, so Nix will use '/home/deck/.local/share/nix/root' as a
chroot store
The documentation for `parseDrvName` does not agree with the implementation when
the derivation name contains a dash which is followed by something that is
neither a letter nor a digit. This commit corrects the documentation to agree
with the implementation.
If we don't have any github token, we won't be able to fetch private
repos, but we are also more likely to run into API limits since
we don't have a token. To mitigate this only ever use the github api
if we actually have a token.
The current definition of `intersectAttrs` is incorrect:
> Return a set consisting of the attributes in the set e2 that also exist in the
> set e1.
Recall that (Nix manual, section 5.1):
> An attribute set is a collection of name-value-pairs (called attributes)
According to the existing description of `intersectAttrs`, the following should
evaluate to the empty set, since no key-value *pair* (i.e. attribute) exists in
both sets:
```
builtins.intersectAttrs { x=3; } {x="foo";}
```
And yet:
```
nix-repl> builtins.intersectAttrs { x=3; } {x="foo";}
{ x = "foo"; }
```
Clearly the intent here was for the *names* of the resulting attribute set to be
the intersection of the *names* of the two arguments, and for the values of the
resulting attribute set to be the values from the second argument.
This commit corrects the definition, making it match the implementation and intent.
Make sure that people who run Nix in non-interactive mode (and so don't have the possibility to interactively accept the individual flake configuration settings) are aware of this flag.
Fix#7086
These settings seem harmless, they control the same polling
functionality that timeout does, but with different behavior. Should
be safe for untrusted users to pass in.
I just had a colleague get confused by the previous phrase for good
reason. "valid" sounds like an *objective* criterion, e.g. and *invalid
signature* would be one that would be trusted by no one, e.g. because it
misformatted or something.
What is actually going is that there might be a signature which is
perfectly valid to *someone else*, but not to the user, because they
don't trust the corresponding public key. This is a *subjective*
criterion, because it depends on the arbitrary and personal choice of
which public keys to trust.
I therefore think "trustworthy" is a better adjective to use. Whether
something is worthy of trust is clearly subjective, and then "trust"
within that word nicely evokes `trusted-public-keys` and friends.
The history is not critical to the functionality of nix repl, so it's
enough to warn here, rather than refuse to start if the directory Nix
thinks the history should live in can't be created.
- call close explicitly in writeFile to prevent the close exception
from being ignored
- fsync after writing schema file to flush data to disk
- fsync schema file parent to flush metadata to disk
https://github.com/NixOS/nix/issues/7064
Remove the `verify TLS: Nix CA file = 'blah'` message that Nix used to print when fetching anything as it's both useless (`libcurl` prints the same info in its logs) and misleading (gives the impression that a new TLS connection is being established which might not be the case because of multiplexing. See #7011 )
This commit adds an optional `__impure` parameter to fetchurl.nix, which allows
the caller to use `libfetcher`'s fetcher in an impure derivation. This allows
nixpkgs' patch-normalizing fetcher (fetchpatch) to be rewritten to use nix's
internal fetchurl, thereby eliminating the awkward "you can't use fetchpatch
here" banners scattered all over the place.
See also: https://github.com/NixOS/nixpkgs/pull/188587
Implements the approach suggested by feedback on PR #6994, where
tempdir paths are created in the store (now with an exclusive lock).
As part of this work, the currently-broken and unused
`createTempDirInStore` function is updated to create an exclusive lock
on the temp directory in the store.
The GC now makes a non-blocking attempt to lock any store directories
that "look like" the temp directories created by this function, and if
it can't acquire one, ignores the directory.
Stdenv sets this to a bash that doesn't have readline/completion
support, so running 'nix (develop|shell)' inside a 'nix develop' gives
you a crippled shell. So let's just ignore the derivation's $SHELL.
This could break interactive use of build phases that use $SHELL, but
they appear to be fairly rare.
Disables the SA_RESTART behavior on macOS which causes:
> Restarting of pending calls is requested by setting the SA_RESTART bit
> in sa_flags. The affected system calls include read(2), write(2),
> sendto(2), recvfrom(2), sendmsg(2) and recvmsg(2) on a communications
> channel or a slow device (such as a terminal, but not a regular file)
> and during a wait(2) or ioctl(2).
From: https://man.openbsd.org/sigaction#SA_RESTART
This being set on macOS caused a bug where read() calls to the daemon
socket were blocking after a SIGINT was received. As a result,
checkInterrupt was never reached even though the signal was received
by the signal handler thread.
On Linux, SA_RESTART is disabled by default. This probably effects
other BSDs but I don’t have the ability to test it there right now.
readDerivation is pretty slow, and while it may not be significant for
some use cases, on things like ghc-nix where we have thousands of
derivations is really slows things down.
So, this just doesn’t do the impure derivation check if the impure
derivation experimental feature is disabled. Perhaps we could cache
the result of isPure() and keep the check, but this is a quick fix to
for the slowdown introduced with impure derivations features in 2.8.0.
this simplifies the setup a lot, and avoids weird looking `./file.md`
links showing up.
it also does not show regular URLs any more. currently the command
reference only has few of them, and not showing them in the offline
documentation is hopefully not a big deal.
instead of building more special-case solutions, clumsily preprocessing
the input, or issuing verbal rules on dealing with URLs, should better
be solved sustainably by not rendering relative links in `lowdown`:
https://github.com/kristapsdz/lowdown/issues/105
This was caused by -L calling setLogFormat() again, which caused the
creation of a new progress bar without destroying the old one. So we
had two progress bars clobbering each other.
We should change 'logger' to be a smart pointer, but I'll do that in a
future PR.
Fixes#6931.
98e361ad4c introduced a regression where
previously stored attributes were replaced by placeholders. As a
result, a command like 'nix build nixpkgs#hello' had to be executed at
least twice to get caching.
This code does not seem necessary for suggestions to work.
This issue made it impossible for clients using a serve protocol of
version <= 2.3 to use the `cmdBuildDerivation` command of servers using
a protocol of version >= 2.6. The faulty version check makes the server
send back build outputs that the client is not expecting.
This hang for some reason didn't trigger in the Nix build, but did
running 'make installcheck' interactively. What happened:
* Store::addMultipleToStore() calls a SinkToSource object to copy a
path, which in turn calls LegacySSHStore::narFromPath(), which
acquires a connection.
* The SinkToSource object is not destroyed after the last bytes has
been read, so the coroutine's stack is still alive and its
destructors are not run. So the connection is not released.
* Then when the next path is copied, because max-connections = 1,
LegacySSHStore::narFromPath() hangs forever waiting for a connection
to be released.
The fix is to make sure that the source object is destroyed when we're
done with it.
Makes `printValueAsJSON` not copy paths to the store for `nix eval
--json`, `nix-instantiate --eval --json` and `nix-env --json`.
Fixes https://github.com/NixOS/nix/issues/5612
RewritingSink can handle being fed input where a reference crosses a
chunk boundary. we don't need to load the whole source into memory, and
in fact *not* loading the whole source lets nix build FODs that do not
fit into memory (eg fetchurl'ing data files larger than system memory).
Some activities are numerous but usually very short (e.g. copying a
source file to the store) which would cause a lot of flickering. So
only show activities that have been running for at least 10 ms.
Rather than directly copying the source to its dest, copy it first to a
temporary location, and eventually move that temporary.
That way, the move is at least atomic from the point-of-view of the destination
The recursive copy from the stl doesn’t exactly do what we need because
1. It doesn’t delete things as we go
2. It doesn’t keep the mtime, which change the nars
So re-implement it ourselves. A bit dull, but that way we have what we want
In `nix::rename`, if the call to `rename` fails with `EXDEV` (failure
because the source and the destination are in a different filesystems)
switch to copying and removing the source.
To avoid having to re-implement the copy manually, I switched the
function to use the c++17 `filesystem` library (which has a `copy`
function that should do what we want).
Fix#6262
Once a derivation goal has been completed, we check whether or not
this goal was meant to be repeated to check its output.
An early return branch was preventing the worker to reach that repeat
code branch, hence breaking the --check command (#2619).
It seems like this early return branch is an artifact of a passed
refactoring. As far as I can tell, buildDone's main branch also
cleanup the tmp directory before returning.
By default, Nix sets the "cores" setting to the number of CPUs which are
physically present on the machine. If cgroups are used to limit the CPU
and memory consumption of a large Nix build, the OOM killer may be
invoked.
For example, consider a GitLab CI pipeline which builds a large software
package. The GitLab runner spawns a container whose CPU is limited to 4
cores and whose memory is limited to 16 GiB. If the underlying machine
has 64 cores, Nix will invoke the build with -j64. In many cases, that
level of parallelism will invoke the OOM killer and the build will
completely fail.
This change sets the default value of "cores" to be
ceil(cpu_quota / cpu_period), with a fallback to
std:🧵:hardware_concurrency() if cgroups v2 is not detected.
The workaround for "Some distros patch Linux" mentioned in
local-derivation-goal.cc will not help in the `--option
sandbox-fallback false` case. To provide the user more helpful
guidance on how to get the sandbox working, let's check to see if the
`/proc` node created by the aforementioned patch is present and
configured in a way that will cause us problems. If so, give the user
a suggestion for how to troubleshoot the problem.
local-derivation-goal.cc contains a comment stating that "Some distros
patch Linux to not allow unprivileged user namespaces." Let's give a
pointer to a common version of this patch for those who want more
details about this failure mode.
This commit causes nix to `warn()` if sandbox setup has failed and
`/proc/self/ns/user` does not exist. This is usually a sign that the
kernel was compiled without `CONFIG_USER_NS=y`, which is required for
sandboxing.
This commit uses `warn()` to notify the user if sandbox setup fails
with errno==EPERM and /proc/sys/user/max_user_namespaces is missing or
zero, since that is at least part of the reason why sandbox setup
failed.
Note that `echo -n 0 > /proc/sys/user/max_user_namespaces` or
equivalent at boot time has been the recommended mitigation for
several Linux LPE vulnerabilities over the past few years. Many users
have applied this mitigation and then forgotten that they have done
so.
The failure modes for nix's sandboxing setup are pretty complicated.
When nix is unable to set up the sandbox, let's provide more detail
about what went wrong. Specifically:
* Make sure the error message includes the word "sandbox" so the user
knows that the failure was related to sandboxing.
* If `--option sandbox-fallback false` was provided, and removing it
would have allowed further attempts to make progress, let the user
know.
