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lix/src/libstore/globals.hh
John Ericson a47e055e09 Move trustedUsers and allowedUsers to separate config struct 
These settings are not needed for libstore at all, they are just used by
the nix daemon *command* for authorization on unix domain sockets. My
moving them to a new configuration struct just in that file, we avoid
them leaking anywhere else.

Also, it is good to break up the mammoth `Settings` struct in general.
Issue #5638 tracks this.

The message is not changed because I do not want to regress in
convenience to the user. Just saying "this connection is not trusted"
doesn't tell them out to fix the issue. The ideal thing to do would be
to somehow parameterize `processCommand` on how the error should be
displayed, so different sorts of connections can display different
information to the user based on how authentication is performed for the
connection in question. This, however, is a good bit more work, so it is
left for the future.

This came up with me thinking about the tcp:// store (#5265). The larger
project is not TCP *per se*, but the idea that it should be possible for
something else to manage access control to services like the Nix Daemon,
and those services simply trust or trust the incoming connection as they
are told. This is a more capability-oriented way of thinking about trust
than "every server implements its own auth separately" as we are used to today.

Its very great that libstore itself already implements just this model,
and so via this refactor I basically want to "enshrine" that so it
continues to be the case.
2023-02-02 14:17:24 -05:00

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#pragma once
#include "types.hh"
#include "config.hh"
#include "util.hh"
#include "experimental-features.hh"
#include <map>
#include <limits>
#include <sys/types.h>
namespace nix {
typedef enum { smEnabled, smRelaxed, smDisabled } SandboxMode;
struct MaxBuildJobsSetting : public BaseSetting<unsigned int>
{
MaxBuildJobsSetting(Config * options,
unsigned int def,
const std::string & name,
const std::string & description,
const std::set<std::string> & aliases = {})
: BaseSetting<unsigned int>(def, true, name, description, aliases)
{
options->addSetting(this);
}
void set(const std::string & str, bool append = false) override;
};
struct PluginFilesSetting : public BaseSetting<Paths>
{
bool pluginsLoaded = false;
PluginFilesSetting(Config * options,
const Paths & def,
const std::string & name,
const std::string & description,
const std::set<std::string> & aliases = {})
: BaseSetting<Paths>(def, true, name, description, aliases)
{
options->addSetting(this);
}
void set(const std::string & str, bool append = false) override;
};
const uint32_t maxIdsPerBuild =
#if __linux__
1 << 16
#else
1
#endif
;
class Settings : public Config {
unsigned int getDefaultCores();
StringSet getDefaultSystemFeatures();
StringSet getDefaultExtraPlatforms();
bool isWSL1();
public:
Settings();
Path nixPrefix;
/* The directory where we store sources and derived files. */
Path nixStore;
Path nixDataDir; /* !!! fix */
/* The directory where we log various operations. */
Path nixLogDir;
/* The directory where state is stored. */
Path nixStateDir;
/* The directory where system configuration files are stored. */
Path nixConfDir;
/* A list of user configuration files to load. */
std::vector<Path> nixUserConfFiles;
/* The directory where the main programs are stored. */
Path nixBinDir;
/* The directory where the man pages are stored. */
Path nixManDir;
/* File name of the socket the daemon listens to. */
Path nixDaemonSocketFile;
Setting<std::string> storeUri{this, getEnv("NIX_REMOTE").value_or("auto"), "store",
"The default Nix store to use."};
Setting<bool> keepFailed{this, false, "keep-failed",
"Whether to keep temporary directories of failed builds."};
Setting<bool> keepGoing{this, false, "keep-going",
"Whether to keep building derivations when another build fails."};
Setting<bool> tryFallback{
this, false, "fallback",
R"(
If set to `true`, Nix will fall back to building from source if a
binary substitute fails. This is equivalent to the `--fallback`
flag. The default is `false`.
)",
{"build-fallback"}};
/* Whether to show build log output in real time. */
bool verboseBuild = true;
Setting<size_t> logLines{this, 10, "log-lines",
"The number of lines of the tail of "
"the log to show if a build fails."};
MaxBuildJobsSetting maxBuildJobs{
this, 1, "max-jobs",
R"(
This option defines the maximum number of jobs that Nix will try to
build in parallel. The default is `1`. The special value `auto`
causes Nix to use the number of CPUs in your system. `0` is useful
when using remote builders to prevent any local builds (except for
`preferLocalBuild` derivation attribute which executes locally
regardless). It can be overridden using the `--max-jobs` (`-j`)
command line switch.
)",
{"build-max-jobs"}};
Setting<unsigned int> buildCores{
this,
getDefaultCores(),
"cores",
R"(
Sets the value of the `NIX_BUILD_CORES` environment variable in the
invocation of builders. Builders can use this variable at their
discretion to control the maximum amount of parallelism. For
instance, in Nixpkgs, if the derivation attribute
`enableParallelBuilding` is set to `true`, the builder passes the
`-jN` flag to GNU Make. It can be overridden using the `--cores`
command line switch and defaults to `1`. The value `0` means that
the builder should use all available CPU cores in the system.
)",
{"build-cores"}, false};
/* Read-only mode. Don't copy stuff to the store, don't change
the database. */
bool readOnlyMode = false;
Setting<std::string> thisSystem{
this, SYSTEM, "system",
R"(
This option specifies the canonical Nix system name of the current
installation, such as `i686-linux` or `x86_64-darwin`. Nix can only
build derivations whose `system` attribute equals the value
specified here. In general, it never makes sense to modify this
value from its default, since you can use it to ‘lie’ about the
platform you are building on (e.g., perform a Mac OS build on a
Linux machine; the result would obviously be wrong). It only makes
sense if the Nix binaries can run on multiple platforms, e.g.,
‘universal binaries’ that run on `x86_64-linux` and `i686-linux`.
It defaults to the canonical Nix system name detected by `configure`
at build time.
)"};
Setting<time_t> maxSilentTime{
this, 0, "max-silent-time",
R"(
This option defines the maximum number of seconds that a builder can
go without producing any data on standard output or standard error.
This is useful (for instance in an automated build system) to catch
builds that are stuck in an infinite loop, or to catch remote builds
that are hanging due to network problems. It can be overridden using
the `--max-silent-time` command line switch.
The value `0` means that there is no timeout. This is also the
default.
)",
{"build-max-silent-time"}};
Setting<time_t> buildTimeout{
this, 0, "timeout",
R"(
This option defines the maximum number of seconds that a builder can
run. This is useful (for instance in an automated build system) to
catch builds that are stuck in an infinite loop but keep writing to
their standard output or standard error. It can be overridden using
the `--timeout` command line switch.
The value `0` means that there is no timeout. This is also the
default.
)",
{"build-timeout"}};
PathSetting buildHook{this, true, "", "build-hook",
"The path of the helper program that executes builds to remote machines."};
Setting<std::string> builders{
this, "@" + nixConfDir + "/machines", "builders",
R"(
A semicolon-separated list of build machines.
For the exact format and examples, see [the manual chapter on remote builds](../advanced-topics/distributed-builds.md)
)"};
Setting<bool> buildersUseSubstitutes{
this, false, "builders-use-substitutes",
R"(
If set to `true`, Nix will instruct remote build machines to use
their own binary substitutes if available. In practical terms, this
means that remote hosts will fetch as many build dependencies as
possible from their own substitutes (e.g, from `cache.nixos.org`),
instead of waiting for this host to upload them all. This can
drastically reduce build times if the network connection between
this computer and the remote build host is slow.
)"};
Setting<off_t> reservedSize{this, 8 * 1024 * 1024, "gc-reserved-space",
"Amount of reserved disk space for the garbage collector."};
Setting<bool> fsyncMetadata{
this, true, "fsync-metadata",
R"(
If set to `true`, changes to the Nix store metadata (in
`/nix/var/nix/db`) are synchronously flushed to disk. This improves
robustness in case of system crashes, but reduces performance. The
default is `true`.
)"};
Setting<bool> useSQLiteWAL{this, !isWSL1(), "use-sqlite-wal",
"Whether SQLite should use WAL mode."};
Setting<bool> syncBeforeRegistering{this, false, "sync-before-registering",
"Whether to call `sync()` before registering a path as valid."};
Setting<bool> useSubstitutes{
this, true, "substitute",
R"(
If set to `true` (default), Nix will use binary substitutes if
available. This option can be disabled to force building from
source.
)",
{"build-use-substitutes"}};
Setting<std::string> buildUsersGroup{
this, "", "build-users-group",
R"(
This options specifies the Unix group containing the Nix build user
accounts. In multi-user Nix installations, builds should not be
performed by the Nix account since that would allow users to
arbitrarily modify the Nix store and database by supplying specially
crafted builders; and they cannot be performed by the calling user
since that would allow him/her to influence the build result.
Therefore, if this option is non-empty and specifies a valid group,
builds will be performed under the user accounts that are a member
of the group specified here (as listed in `/etc/group`). Those user
accounts should not be used for any other purpose\!
Nix will never run two builds under the same user account at the
same time. This is to prevent an obvious security hole: a malicious
user writing a Nix expression that modifies the build result of a
legitimate Nix expression being built by another user. Therefore it
is good to have as many Nix build user accounts as you can spare.
(Remember: uids are cheap.)
The build users should have permission to create files in the Nix
store, but not delete them. Therefore, `/nix/store` should be owned
by the Nix account, its group should be the group specified here,
and its mode should be `1775`.
If the build users group is empty, builds will be performed under
the uid of the Nix process (that is, the uid of the caller if
`NIX_REMOTE` is empty, the uid under which the Nix daemon runs if
`NIX_REMOTE` is `daemon`). Obviously, this should not be used
with a nix daemon accessible to untrusted clients.
Defaults to `nixbld` when running as root, *empty* otherwise.
)",
{}, false};
Setting<bool> autoAllocateUids{this, false, "auto-allocate-uids",
R"(
Whether to select UIDs for builds automatically, instead of using the
users in `build-users-group`.
UIDs are allocated starting at 872415232 (0x34000000) on Linux and 56930 on macOS.
> **Warning**
> This is an experimental feature.
To enable it, add the following to [`nix.conf`](#):
```
extra-experimental-features = auto-allocate-uids
auto-allocate-uids = true
```
)"};
Setting<uint32_t> startId{this,
#if __linux__
0x34000000,
#else
56930,
#endif
"start-id",
"The first UID and GID to use for dynamic ID allocation."};
Setting<uint32_t> uidCount{this,
#if __linux__
maxIdsPerBuild * 128,
#else
128,
#endif
"id-count",
"The number of UIDs/GIDs to use for dynamic ID allocation."};
#if __linux__
Setting<bool> useCgroups{
this, false, "use-cgroups",
R"(
Whether to execute builds inside cgroups.
This is only supported on Linux.
Cgroups are required and enabled automatically for derivations
that require the `uid-range` system feature.
> **Warning**
> This is an experimental feature.
To enable it, add the following to [`nix.conf`](#):
```
extra-experimental-features = cgroups
use-cgroups = true
```
)"};
#endif
Setting<bool> impersonateLinux26{this, false, "impersonate-linux-26",
"Whether to impersonate a Linux 2.6 machine on newer kernels.",
{"build-impersonate-linux-26"}};
Setting<bool> keepLog{
this, true, "keep-build-log",
R"(
If set to `true` (the default), Nix will write the build log of a
derivation (i.e. the standard output and error of its builder) to
the directory `/nix/var/log/nix/drvs`. The build log can be
retrieved using the command `nix-store -l path`.
)",
{"build-keep-log"}};
Setting<bool> compressLog{
this, true, "compress-build-log",
R"(
If set to `true` (the default), build logs written to
`/nix/var/log/nix/drvs` will be compressed on the fly using bzip2.
Otherwise, they will not be compressed.
)",
{"build-compress-log"}};
Setting<unsigned long> maxLogSize{
this, 0, "max-build-log-size",
R"(
This option defines the maximum number of bytes that a builder can
write to its stdout/stderr. If the builder exceeds this limit, it’s
killed. A value of `0` (the default) means that there is no limit.
)",
{"build-max-log-size"}};
Setting<unsigned int> pollInterval{this, 5, "build-poll-interval",
"How often (in seconds) to poll for locks."};
Setting<bool> gcKeepOutputs{
this, false, "keep-outputs",
R"(
If `true`, the garbage collector will keep the outputs of
non-garbage derivations. If `false` (default), outputs will be
deleted unless they are GC roots themselves (or reachable from other
roots).
In general, outputs must be registered as roots separately. However,
even if the output of a derivation is registered as a root, the
collector will still delete store paths that are used only at build
time (e.g., the C compiler, or source tarballs downloaded from the
network). To prevent it from doing so, set this option to `true`.
)",
{"gc-keep-outputs"}};
Setting<bool> gcKeepDerivations{
this, true, "keep-derivations",
R"(
If `true` (default), the garbage collector will keep the derivations
from which non-garbage store paths were built. If `false`, they will
be deleted unless explicitly registered as a root (or reachable from
other roots).
Keeping derivation around is useful for querying and traceability
(e.g., it allows you to ask with what dependencies or options a
store path was built), so by default this option is on. Turn it off
to save a bit of disk space (or a lot if `keep-outputs` is also
turned on).
)",
{"gc-keep-derivations"}};
Setting<bool> autoOptimiseStore{
this, false, "auto-optimise-store",
R"(
If set to `true`, Nix automatically detects files in the store
that have identical contents, and replaces them with hard links to
a single copy. This saves disk space. If set to `false` (the
default), you can still run `nix-store --optimise` to get rid of
duplicate files.
)"};
Setting<bool> envKeepDerivations{
this, false, "keep-env-derivations",
R"(
If `false` (default), derivations are not stored in Nix user
environments. That is, the derivations of any build-time-only
dependencies may be garbage-collected.
If `true`, when you add a Nix derivation to a user environment, the
path of the derivation is stored in the user environment. Thus, the
derivation will not be garbage-collected until the user environment
generation is deleted (`nix-env --delete-generations`). To prevent
build-time-only dependencies from being collected, you should also
turn on `keep-outputs`.
The difference between this option and `keep-derivations` is that
this one is “sticky”: it applies to any user environment created
while this option was enabled, while `keep-derivations` only applies
at the moment the garbage collector is run.
)",
{"env-keep-derivations"}};
/* Whether to lock the Nix client and worker to the same CPU. */
bool lockCPU;
Setting<SandboxMode> sandboxMode{
this,
#if __linux__
smEnabled
#else
smDisabled
#endif
, "sandbox",
R"(
If set to `true`, builds will be performed in a *sandboxed
environment*, i.e., they’re isolated from the normal file system
hierarchy and will only see their dependencies in the Nix store,
the temporary build directory, private versions of `/proc`,
`/dev`, `/dev/shm` and `/dev/pts` (on Linux), and the paths
configured with the `sandbox-paths` option. This is useful to
prevent undeclared dependencies on files in directories such as
`/usr/bin`. In addition, on Linux, builds run in private PID,
mount, network, IPC and UTS namespaces to isolate them from other
processes in the system (except that fixed-output derivations do
not run in private network namespace to ensure they can access the
network).
Currently, sandboxing only work on Linux and macOS. The use of a
sandbox requires that Nix is run as root (so you should use the
“build users” feature to perform the actual builds under different
users than root).
If this option is set to `relaxed`, then fixed-output derivations
and derivations that have the `__noChroot` attribute set to `true`
do not run in sandboxes.
The default is `true` on Linux and `false` on all other platforms.
)",
{"build-use-chroot", "build-use-sandbox"}};
Setting<PathSet> sandboxPaths{
this, {}, "sandbox-paths",
R"(
A list of paths bind-mounted into Nix sandbox environments. You can
use the syntax `target=source` to mount a path in a different
location in the sandbox; for instance, `/bin=/nix-bin` will mount
the path `/nix-bin` as `/bin` inside the sandbox. If *source* is
followed by `?`, then it is not an error if *source* does not exist;
for example, `/dev/nvidiactl?` specifies that `/dev/nvidiactl` will
only be mounted in the sandbox if it exists in the host filesystem.
If the source is in the Nix store, then its closure will be added to
the sandbox as well.
Depending on how Nix was built, the default value for this option
may be empty or provide `/bin/sh` as a bind-mount of `bash`.
)",
{"build-chroot-dirs", "build-sandbox-paths"}};
Setting<bool> sandboxFallback{this, true, "sandbox-fallback",
"Whether to disable sandboxing when the kernel doesn't allow it."};
#if __linux__
Setting<std::string> sandboxShmSize{
this, "50%", "sandbox-dev-shm-size",
R"(
This option determines the maximum size of the `tmpfs` filesystem
mounted on `/dev/shm` in Linux sandboxes. For the format, see the
description of the `size` option of `tmpfs` in mount8. The default
is `50%`.
)"};
Setting<Path> sandboxBuildDir{this, "/build", "sandbox-build-dir",
"The build directory inside the sandbox."};
#endif
Setting<PathSet> allowedImpureHostPrefixes{this, {}, "allowed-impure-host-deps",
"Which prefixes to allow derivations to ask for access to (primarily for Darwin)."};
#if __APPLE__
Setting<bool> darwinLogSandboxViolations{this, false, "darwin-log-sandbox-violations",
"Whether to log Darwin sandbox access violations to the system log."};
#endif
Setting<bool> runDiffHook{
this, false, "run-diff-hook",
R"(
If true, enable the execution of the `diff-hook` program.
When using the Nix daemon, `run-diff-hook` must be set in the
`nix.conf` configuration file, and cannot be passed at the command
line.
)"};
PathSetting diffHook{
this, true, "", "diff-hook",
R"(
Absolute path to an executable capable of diffing build
results. The hook is executed if `run-diff-hook` is true, and the
output of a build is known to not be the same. This program is not
executed to determine if two results are the same.
The diff hook is executed by the same user and group who ran the
build. However, the diff hook does not have write access to the
store path just built.
The diff hook program receives three parameters:
1. A path to the previous build's results
2. A path to the current build's results
3. The path to the build's derivation
4. The path to the build's scratch directory. This directory will
exist only if the build was run with `--keep-failed`.
The stderr and stdout output from the diff hook will not be
displayed to the user. Instead, it will print to the nix-daemon's
log.
When using the Nix daemon, `diff-hook` must be set in the `nix.conf`
configuration file, and cannot be passed at the command line.
)"};
Setting<Strings> trustedPublicKeys{
this,
{"cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="},
"trusted-public-keys",
R"(
A whitespace-separated list of public keys.
At least one of the following condition must be met
for Nix to accept copying a store object from another
Nix store (such as a substituter):
- the store object has been signed using a key in the trusted keys list
- the [`require-sigs`](#conf-require-sigs) option has been set to `false`
- the store object is [output-addressed](@docroot@/glossary.md#gloss-output-addressed-store-object)
)",
{"binary-cache-public-keys"}};
Setting<Strings> secretKeyFiles{
this, {}, "secret-key-files",
R"(
A whitespace-separated list of files containing secret (private)
keys. These are used to sign locally-built paths. They can be
generated using `nix-store --generate-binary-cache-key`. The
corresponding public key can be distributed to other users, who
can add it to `trusted-public-keys` in their `nix.conf`.
)"};
Setting<unsigned int> tarballTtl{
this, 60 * 60, "tarball-ttl",
R"(
The number of seconds a downloaded tarball is considered fresh. If
the cached tarball is stale, Nix will check whether it is still up
to date using the ETag header. Nix will download a new version if
the ETag header is unsupported, or the cached ETag doesn't match.
Setting the TTL to `0` forces Nix to always check if the tarball is
up to date.
Nix caches tarballs in `$XDG_CACHE_HOME/nix/tarballs`.
Files fetched via `NIX_PATH`, `fetchGit`, `fetchMercurial`,
`fetchTarball`, and `fetchurl` respect this TTL.
)"};
Setting<bool> requireSigs{
this, true, "require-sigs",
R"(
If set to `true` (the default), any non-content-addressed path added
or copied to the Nix store (e.g. when substituting from a binary
cache) must have a signature by a trusted key. A trusted key is one
listed in `trusted-public-keys`, or a public key counterpart to a
private key stored in a file listed in `secret-key-files`.
Set to `false` to disable signature checking and trust all
non-content-addressed paths unconditionally.
(Content-addressed paths are inherently trustworthy and thus
unaffected by this configuration option.)
)"};
Setting<StringSet> extraPlatforms{
this,
getDefaultExtraPlatforms(),
"extra-platforms",
R"(
Platforms other than the native one which this machine is capable of
building for. This can be useful for supporting additional
architectures on compatible machines: i686-linux can be built on
x86\_64-linux machines (and the default for this setting reflects
this); armv7 is backwards-compatible with armv6 and armv5tel; some
aarch64 machines can also natively run 32-bit ARM code; and
qemu-user may be used to support non-native platforms (though this
may be slow and buggy). Most values for this are not enabled by
default because build systems will often misdetect the target
platform and generate incompatible code, so you may wish to
cross-check the results of using this option against proper
natively-built versions of your derivations.
)", {}, false};
Setting<StringSet> systemFeatures{
this,
getDefaultSystemFeatures(),
"system-features",
R"(
A set of system “features” supported by this machine, e.g. `kvm`.
Derivations can express a dependency on such features through the
derivation attribute `requiredSystemFeatures`. For example, the
attribute
requiredSystemFeatures = [ "kvm" ];
ensures that the derivation can only be built on a machine with the
`kvm` feature.
This setting by default includes `kvm` if `/dev/kvm` is accessible,
and the pseudo-features `nixos-test`, `benchmark` and `big-parallel`
that are used in Nixpkgs to route builds to specific machines.
)", {}, false};
Setting<Strings> substituters{
this,
Strings{"https://cache.nixos.org/"},
"substituters",
R"(
A list of URLs of substituters, separated by whitespace. Substituters
are tried based on their Priority value, which each substituter can set
independently. Lower value means higher priority.
The default is `https://cache.nixos.org`, with a Priority of 40.
At least one of the following conditions must be met for Nix to use
a substituter:
- the substituter is in the [`trusted-substituters`](#conf-trusted-substituters) list
- the user calling Nix is in the [`trusted-users`](#conf-trusted-users) list
In addition, each store path should be trusted as described
in [`trusted-public-keys`](#conf-trusted-public-keys)
)",
{"binary-caches"}};
Setting<StringSet> trustedSubstituters{
this, {}, "trusted-substituters",
R"(
A list of URLs of substituters, separated by whitespace. These are
not used by default, but can be enabled by users of the Nix daemon
by specifying `--option substituters urls` on the command
line. Unprivileged users are only allowed to pass a subset of the
URLs listed in `substituters` and `trusted-substituters`.
)",
{"trusted-binary-caches"}};
Setting<unsigned int> ttlNegativeNarInfoCache{
this, 3600, "narinfo-cache-negative-ttl",
R"(
The TTL in seconds for negative lookups. If a store path is queried
from a substituter but was not found, there will be a negative
lookup cached in the local disk cache database for the specified
duration.
)"};
Setting<unsigned int> ttlPositiveNarInfoCache{
this, 30 * 24 * 3600, "narinfo-cache-positive-ttl",
R"(
The TTL in seconds for positive lookups. If a store path is queried
from a substituter, the result of the query will be cached in the
local disk cache database including some of the NAR metadata. The
default TTL is a month, setting a shorter TTL for positive lookups
can be useful for binary caches that have frequent garbage
collection, in which case having a more frequent cache invalidation
would prevent trying to pull the path again and failing with a hash
mismatch if the build isn't reproducible.
)"};
Setting<bool> printMissing{this, true, "print-missing",
"Whether to print what paths need to be built or downloaded."};
Setting<std::string> preBuildHook{
this, "", "pre-build-hook",
R"(
If set, the path to a program that can set extra derivation-specific
settings for this system. This is used for settings that can't be
captured by the derivation model itself and are too variable between
different versions of the same system to be hard-coded into nix.
The hook is passed the derivation path and, if sandboxes are
enabled, the sandbox directory. It can then modify the sandbox and
send a series of commands to modify various settings to stdout. The
currently recognized commands are:
- `extra-sandbox-paths`\
Pass a list of files and directories to be included in the
sandbox for this build. One entry per line, terminated by an
empty line. Entries have the same format as `sandbox-paths`.
)"};
Setting<std::string> postBuildHook{
this, "", "post-build-hook",
R"(
Optional. The path to a program to execute after each build.
This option is only settable in the global `nix.conf`, or on the
command line by trusted users.
When using the nix-daemon, the daemon executes the hook as `root`.
If the nix-daemon is not involved, the hook runs as the user
executing the nix-build.
- The hook executes after an evaluation-time build.
- The hook does not execute on substituted paths.
- The hook's output always goes to the user's terminal.
- If the hook fails, the build succeeds but no further builds
execute.
- The hook executes synchronously, and blocks other builds from
progressing while it runs.
The program executes with no arguments. The program's environment
contains the following environment variables:
- `DRV_PATH`
The derivation for the built paths.
Example:
`/nix/store/5nihn1a7pa8b25l9zafqaqibznlvvp3f-bash-4.4-p23.drv`
- `OUT_PATHS`
Output paths of the built derivation, separated by a space
character.
Example:
`/nix/store/zf5lbh336mnzf1nlswdn11g4n2m8zh3g-bash-4.4-p23-dev
/nix/store/rjxwxwv1fpn9wa2x5ssk5phzwlcv4mna-bash-4.4-p23-doc
/nix/store/6bqvbzjkcp9695dq0dpl5y43nvy37pq1-bash-4.4-p23-info
/nix/store/r7fng3kk3vlpdlh2idnrbn37vh4imlj2-bash-4.4-p23-man
/nix/store/xfghy8ixrhz3kyy6p724iv3cxji088dx-bash-4.4-p23`.
)"};
Setting<unsigned int> downloadSpeed {
this, 0, "download-speed",
R"(
Specify the maximum transfer rate in kilobytes per second you want
Nix to use for downloads.
)"};
Setting<std::string> netrcFile{
this, fmt("%s/%s", nixConfDir, "netrc"), "netrc-file",
R"(
If set to an absolute path to a `netrc` file, Nix will use the HTTP
authentication credentials in this file when trying to download from
a remote host through HTTP or HTTPS. Defaults to
`$NIX_CONF_DIR/netrc`.
The `netrc` file consists of a list of accounts in the following
format:
machine my-machine
login my-username
password my-password
For the exact syntax, see [the `curl`
documentation](https://ec.haxx.se/usingcurl-netrc.html).
> **Note**
>
> This must be an absolute path, and `~` is not resolved. For
> example, `~/.netrc` won't resolve to your home directory's
> `.netrc`.
)"};
/* Path to the SSL CA file used */
Path caFile;
#if __linux__
Setting<bool> filterSyscalls{
this, true, "filter-syscalls",
R"(
Whether to prevent certain dangerous system calls, such as
creation of setuid/setgid files or adding ACLs or extended
attributes. Only disable this if you're aware of the
security implications.
)"};
Setting<bool> allowNewPrivileges{
this, false, "allow-new-privileges",
R"(
(Linux-specific.) By default, builders on Linux cannot acquire new
privileges by calling setuid/setgid programs or programs that have
file capabilities. For example, programs such as `sudo` or `ping`
will fail. (Note that in sandbox builds, no such programs are
available unless you bind-mount them into the sandbox via the
`sandbox-paths` option.) You can allow the use of such programs by
enabling this option. This is impure and usually undesirable, but
may be useful in certain scenarios (e.g. to spin up containers or
set up userspace network interfaces in tests).
)"};
Setting<StringSet> ignoredAcls{
this, {"security.selinux", "system.nfs4_acl", "security.csm"}, "ignored-acls",
R"(
A list of ACLs that should be ignored, normally Nix attempts to
remove all ACLs from files and directories in the Nix store, but
some ACLs like `security.selinux` or `system.nfs4_acl` can't be
removed even by root. Therefore it's best to just ignore them.
)"};
#endif
Setting<Strings> hashedMirrors{
this, {}, "hashed-mirrors",
R"(
A list of web servers used by `builtins.fetchurl` to obtain files by
hash. The default is `http://tarballs.nixos.org/`. Given a hash type
*ht* and a base-16 hash *h*, Nix will try to download the file from
*hashed-mirror*/*ht*/*h*. This allows files to be downloaded even if
they have disappeared from their original URI. For example, given
the default mirror `http://tarballs.nixos.org/`, when building the
derivation
```nix
builtins.fetchurl {
url = "https://example.org/foo-1.2.3.tar.xz";
sha256 = "2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae";
}
```
Nix will attempt to download this file from
`http://tarballs.nixos.org/sha256/2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae`
first. If it is not available there, if will try the original URI.
)"};
Setting<uint64_t> minFree{
this, 0, "min-free",
R"(
When free disk space in `/nix/store` drops below `min-free` during a
build, Nix performs a garbage-collection until `max-free` bytes are
available or there is no more garbage. A value of `0` (the default)
disables this feature.
)"};
Setting<uint64_t> maxFree{
this, std::numeric_limits<uint64_t>::max(), "max-free",
R"(
When a garbage collection is triggered by the `min-free` option, it
stops as soon as `max-free` bytes are available. The default is
infinity (i.e. delete all garbage).
)"};
Setting<uint64_t> minFreeCheckInterval{this, 5, "min-free-check-interval",
"Number of seconds between checking free disk space."};
PluginFilesSetting pluginFiles{
this, {}, "plugin-files",
R"(
A list of plugin files to be loaded by Nix. Each of these files will
be dlopened by Nix, allowing them to affect execution through static
initialization. In particular, these plugins may construct static
instances of RegisterPrimOp to add new primops or constants to the
expression language, RegisterStoreImplementation to add new store
implementations, RegisterCommand to add new subcommands to the `nix`
command, and RegisterSetting to add new nix config settings. See the
constructors for those types for more details.
Warning! These APIs are inherently unstable and may change from
release to release.
Since these files are loaded into the same address space as Nix
itself, they must be DSOs compatible with the instance of Nix
running at the time (i.e. compiled against the same headers, not
linked to any incompatible libraries). They should not be linked to
any Nix libs directly, as those will be available already at load
time.
If an entry in the list is a directory, all files in the directory
are loaded as plugins (non-recursively).
)"};
Setting<std::set<ExperimentalFeature>> experimentalFeatures{this, {}, "experimental-features",
"Experimental Nix features to enable."};
bool isExperimentalFeatureEnabled(const ExperimentalFeature &);
void requireExperimentalFeature(const ExperimentalFeature &);
Setting<size_t> narBufferSize{this, 32 * 1024 * 1024, "nar-buffer-size",
"Maximum size of NARs before spilling them to disk."};
Setting<bool> allowSymlinkedStore{
this, false, "allow-symlinked-store",
R"(
If set to `true`, Nix will stop complaining if the store directory
(typically /nix/store) contains symlink components.
This risks making some builds "impure" because builders sometimes
"canonicalise" paths by resolving all symlink components. Problems
occur if those builds are then deployed to machines where /nix/store
resolves to a different location from that of the build machine. You
can enable this setting if you are sure you're not going to do that.
)"};
};
// FIXME: don't use a global variable.
extern Settings settings;
/* This should be called after settings are initialized, but before
anything else */
void initPlugins();
void loadConfFile();
// Used by the Settings constructor
std::vector<Path> getUserConfigFiles();
extern const std::string nixVersion;
/* NB: This is not sufficient. You need to call initNix() */
void initLibStore();
/* It's important to initialize before doing _anything_, which is why we
call upon the programmer to handle this correctly. However, we only add
this in a key locations, so as not to litter the code. */
void assertLibStoreInitialized();
}
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