For each output, this adds a corresponding attribute to the derivation that is
the same as the derivation except for outPath, which is set to the path specific
to that output. Additionally, an "all" attribute is added that is a list of all
of the output derivations. This has to be done outside of derivationStrict as
each output is itself a derivation that contains itself (and all other outputs)
as an attribute. The derivation itself is equivalent to the first output in the
outputs list (or "out" if that list isn't set).
the contents of any of the given store paths have been modified.
E.g.
$ nix-store --verify-path $(nix-store -qR /var/run/current-system)
path `/nix/store/m2smyiwbxidlprfxfz4rjlvz2c3mg58y-etc' was modified! expected hash `fc87e271c5fdf179b47939b08ad13440493805584b35e3014109d04d8436e7b8', got `20f1a47281b3c0cbe299ce47ad5ca7340b20ab34246426915fce0ee9116483aa'
All paths are checked; the exit code is 1 if any path has been
modified, 0 otherwise.
This should also fix:
nix-instantiate: ./../boost/shared_ptr.hpp:254: T* boost::shared_ptr<T>::operator->() const [with T = nix::StoreAPI]: Assertion `px != 0' failed.
which was caused by hashDerivationModulo() calling the ‘store’
object (during store upgrades) before openStore() assigned it.
prevents files from being evaluated and stored as values multiple
times. For instance, evaluation of the ‘system’ attribute in NixOS
causes ‘nixpkgs/pkgs/lib/lists.nix’ to be evaluated 2019 times.
Caching gives a modest speedup and a decent memory footprint
reduction (e.g., from 1.44s to 1.28s, and from 81 MiB to 59 MiB with
GC_INITIAL_HEAP_SIZE=100000 on my system).
directory
/home/eelco/src/stdenv-updates
that you want to use as the directory for import such as
with (import <nixpkgs> { });
then you can say
$ nix-build -I nixpkgs=/home/eelco/src/stdenv-updates
brackets, e.g.
import <nixpkgs/pkgs/lib>
are resolved by looking them up relative to the elements listed in
the search path. This allows us to get rid of hacks like
import "${builtins.getEnv "NIXPKGS_ALL"}/pkgs/lib"
The search path can be specified through the ‘-I’ command-line flag
and through the colon-separated ‘NIX_PATH’ environment variable,
e.g.,
$ nix-build -I /etc/nixos ...
If a file is not found in the search path, an error message is
lazily thrown.
derivations added to the store by clients have "correct" output
paths (meaning that the output paths are computed by hashing the
derivation according to a certain algorithm). This means that a
malicious user could craft a special .drv file to build *any*
desired path in the store with any desired contents (so long as the
path doesn't already exist). Then the attacker just needs to wait
for a victim to come along and install the compromised path.
For instance, if Alice (the attacker) knows that the latest Firefox
derivation in Nixpkgs produces the path
/nix/store/1a5nyfd4ajxbyy97r1fslhgrv70gj8a7-firefox-5.0.1
then (provided this path doesn't already exist) she can craft a .drv
file that creates that path (i.e., has it as one of its outputs),
add it to the store using "nix-store --add", and build it with
"nix-store -r". So the fake .drv could write a Trojan to the
Firefox path. Then, if user Bob (the victim) comes along and does
$ nix-env -i firefox
$ firefox
he executes the Trojan injected by Alice.
The fix is to have the Nix daemon verify that derivation outputs are
correct (in addValidPath()). This required some refactoring to move
the hash computation code to libstore.
by setting the ‘outputs’ attribute. For example:
stdenv.mkDerivation {
name = "aterm-2.5";
src = ...;
outputs = [ "out" "tools" "dev" ];
configureFlags = "--bindir=$(tools)/bin --includedir=$(dev)/include";
}
This derivation creates three outputs, named like this:
/nix/store/gcnqgllbh01p3d448q8q6pzn2nc2gpyl-aterm-2.5
/nix/store/gjf1sgirwfnrlr0bdxyrwzpw2r304j02-aterm-2.5-tools
/nix/store/hp6108bqfgxvza25nnxfs7kj88xi2vdx-aterm-2.5-dev
That is, the symbolic name of the output is suffixed to the store
path (except for the ‘out’ output). Each path is passed to the
builder through the corresponding environment variable, e.g.,
${tools}.
The main reason for multiple outputs is to allow parts of a package
to be distributed and garbage-collected separately. For instance,
most packages depend on Glibc for its libraries, but don't need its
header files. If these are separated into different store paths,
then a package that depends on the Glibc libraries only causes the
libraries and not the headers to be downloaded.
The main problem with multiple outputs is that if one output exists
while the others have been garbage-collected (or never downloaded in
the first place), and we want to rebuild the other outputs, then
this isn't possible because we can't clobber a valid output (it
might be in active use). This currently gives an error message
like:
error: derivation `/nix/store/1s9zw4c8qydpjyrayxamx2z7zzp5pcgh-aterm-2.5.drv' is blocked by its output paths
There are two solutions: 1) Do the build in a chroot. Then we don't
need to overwrite the existing path. 2) Use hash rewriting (see the
ASE-2005 paper). Scary but it should work.
This is not finished yet. There is not yet an easy way to refer to
non-default outputs in Nix expressions. Also, mutually recursive
outputs aren't detected yet and cause the garbage collector to
crash.
write ‘attrs ? a.b’ to test whether ‘attrs’ has an attribute ‘a’
containing an attribute ‘b’. This is more convenient than ‘attrs ?
a && attrs.a ? b’.
Slight change in the semantics: it's no longer an error if the
left-hand side of ‘?’ is not an attribute set. In that case it just
returns false. So, ‘null ? foo’ no longer throws an error.
checked too soon whether substitutes are available. That is, it did
so for every available package, rather than those matching installed
packages. This was very slow and subject to assertion failures. So
do the check much later. Idem for `nix-env -qab' and `nix-env -ib'.
little RAM. Even if the memory isn't actually used, it can cause
problems with the overcommit heuristics in the kernel. So use a VM
space of 25% of RAM, up to 384 MB.
while checking the contents, since this operation can take a very
long time to finish. Also, fill in missing narSize fields in the DB
while doing this.
even with a very long busy timeout, because SQLITE_BUSY is also
returned to resolve deadlocks. This should get rid of random
"database is locked" errors. This is kind of hard to test though.
* Fix a horrible bug in deleteFromStore(): deletePathWrapped() should
be called after committing the transaction, not before, because the
commit might not succeed.
tree). This saves a lot of memory. The vector should be sorted so
that names can be looked up using binary search, but this is not the
case yet. (Surprisingly, looking up attributes using linear search
doesn't have a big impact on performance.)
Memory consumption for
$ nix-instantiate /etc/nixos/nixos/tests -A bittorrent.test --readonly-mode
on x86_64-linux with GC enabled is now 185 MiB (compared to 946
MiB on the trunk).
improves GC effectiveness a bit more (because a live value doesn't
keep other values in the environment plus the parent environments
alive), and removes the need for copy nodes.
a pointer to a Value, rather than the Value directly. This improves
the effectiveness of garbage collection a lot: if the Value is
stored inside the set directly, then any live pointer to the Value
causes all other attributes in the set to be live as well.
race with other processes that add new referrers to a path,
resulting in the garbage collector crashing with "foreign key
constraint failed". (Nix/4)
* Make --gc --print-dead etc. interruptible.
because it defines _FILE_OFFSET_BITS. Without this, on
OpenSolaris the system headers define it to be 32, and then
the 32-bit stat() ends up being called with a 64-bit "struct
stat", or vice versa.
This also ensures that we get 64-bit file sizes everywhere.
* Remove the redundant call to stat() in parseExprFromFile().
The file cannot be a symlink because that's the exit condition
of the loop before.
exception handler, otherwise throw an exception. We need to ignore
write errors in exception handlers to ensure that cleanup code runs
to completion if the other side of stderr has been closed
unexpectedly.
* If a path has disappeared, check its referrers first, and don't try
to invalidate paths that have valid referrers. Otherwise we get a
foreign key constraint violation.
* Read the whole Nix store directory instead of statting each valid
path, which is slower.
* Acquire the global GC lock.
hook script proper, and the stdout/stderr of the builder. Only the
latter should be saved in /nix/var/log/nix/drvs.
* Allow the verbosity to be set through an option.
* Added a flag --quiet to lower the verbosity level.
it requires a certain feature on the build machine, e.g.
requiredSystemFeatures = [ "kvm" ];
We need this in Hydra to make sure that builds that require KVM
support are forwarded to machines that have KVM support. Probably
this should also be enforced for local builds.
the hook every time we want to ask whether we can run a remote build
(which can be very often), we now reuse a hook process for answering
those queries until it accepts a build. So if there are N
derivations to be built, at most N hooks will be started.
faster than the old mode when fsyncs are enabled, because it only
performs an fsync() when doing a checkpoint, rather than at every
commit. Some timings for doing a "nix-instantiate /etc/nixos/nixos
-A system" after modifying the stdenv setup script:
42.5s - SQLite 3.6.23 with truncate mode and fsync
3.4s - SQLite 3.6.23 with truncate mode and no fsync
32.1s - SQLite 3.7.0 with truncate mode and fsync
16.8s - SQLite 3.7.0 with WAL mode and fsync, auto-checkpoint
every 1000 pages
8.3s - SQLite 3.7.0 with WAL mode and fsync, auto-checkpoint
every 8192 pages
1.7s - SQLite 3.7.0 with WAL mode and no fsync
The default is now to use WAL mode with fsyncs. Because WAL doesn't
work on remote filesystems such as NFS (as it uses shared memory),
truncate mode can be re-enabled by setting the "use-sqlite-wal"
option to false.
using the build hook mechanism, by setting the derivation attribute
"preferLocalBuild" to true. This has a few use cases:
- The user environment builder. Since it just creates a bunch of
symlinks without much computation, there is no reason to do it
remotely. In fact, doing it remotely requires the entire closure
of the user environment to be copied to the remote machine, which
is extremely wasteful.
- `fetchurl'. Performing the download on a remote machine and then
copying it to the local machine involves twice as much network
traffic as performing the download locally, and doesn't save any
CPU cycles on the local machine.
instance) "nix-env -i wine" works on x86_64-linux, even though Wine
is built on i686-linux. In the event that there are multiple
matching derivations, prefer those built for the current system.
