nix-super/doc/manual/src/release-notes/rl-1.7.md

Release 1.7 (2014-04-11)

In addition to the usual bug fixes, this release has the following new features:

• Antiquotation is now allowed inside of quoted attribute names (e.g. set."${foo}"). In the case where the attribute name is just a single antiquotation, the quotes can be dropped (e.g. the above example can be written set.${foo}). If an attribute name inside of a set declaration evaluates to null (e.g. { ${null} = false; }), then that attribute is not added to the set.

• Experimental support for cryptographically signed binary caches. See the commit for details.

• An experimental new substituter, download-via-ssh, that fetches binaries from remote machines via SSH. Specifying the flags --option use-ssh-substituter true --option ssh-substituter-hosts user@hostname will cause Nix to download binaries from the specified machine, if it has them.

• nix-store -r and nix-build have a new flag, --check, that builds a previously built derivation again, and prints an error message if the output is not exactly the same. This helps to verify whether a derivation is truly deterministic. For example:

  $ nix-build '<nixpkgs>' -A patchelf
  …
  $ nix-build '<nixpkgs>' -A patchelf --check
  …
  error: derivation `/nix/store/1ipvxs…-patchelf-0.6' may not be deterministic:
    hash mismatch in output `/nix/store/4pc1dm…-patchelf-0.6.drv'
  

• The nix-instantiate flags --eval-only and --parse-only have been renamed to --eval and --parse, respectively.

• nix-instantiate, nix-build and nix-shell now have a flag --expr (or -E) that allows you to specify the expression to be evaluated as a command line argument. For instance, nix-instantiate --eval -E '1 + 2' will print 3.

• nix-shell improvements:

  • It has a new flag, --packages (or -p), that sets up a build environment containing the specified packages from Nixpkgs. For example, the command

    $ nix-shell -p sqlite xorg.libX11 hello
    

    will start a shell in which the given packages are present.

  • It now uses shell.nix as the default expression, falling back to default.nix if the former doesn’t exist. This makes it convenient to have a shell.nix in your project to set up a nice development environment.

  • It evaluates the derivation attribute shellHook, if set. Since stdenv does not normally execute this hook, it allows you to do nix-shell-specific setup.

  • It preserves the user’s timezone setting.

• In chroots, Nix now sets up a /dev containing only a minimal set of devices (such as /dev/null). Note that it only does this if you don’t have /dev listed in your build-chroot-dirs setting; otherwise, it will bind-mount the /dev from outside the chroot.

  Similarly, if you don’t have /dev/pts listed in build-chroot-dirs, Nix will mount a private devpts filesystem on the chroot’s /dev/pts.

• New built-in function: builtins.toJSON, which returns a JSON representation of a value.

• nix-env -q has a new flag --json to print a JSON representation of the installed or available packages.

• nix-env now supports meta attributes with more complex values, such as attribute sets.

• The -A flag now allows attribute names with dots in them, e.g.

  $ nix-instantiate --eval '<nixos>' -A 'config.systemd.units."nscd.service".text'
  

• The --max-freed option to nix-store --gc now accepts a unit specifier. For example, nix-store --gc --max-freed 1G will free up to 1 gigabyte of disk space.

• nix-collect-garbage has a new flag --delete-older-than Nd, which deletes all user environment generations older than N days. Likewise, nix-env --delete-generations accepts a Nd age limit.

• Nix now heuristically detects whether a build failure was due to a disk-full condition. In that case, the build is not flagged as “permanently failed”. This is mostly useful for Hydra, which needs to distinguish between permanent and transient build failures.

• There is a new symbol __curPos that expands to an attribute set containing its file name and line and column numbers, e.g. { file = "foo.nix"; line = 10; column = 5; }. There also is a new builtin function, unsafeGetAttrPos, that returns the position of an attribute. This is used by Nixpkgs to provide location information in error messages, e.g.

  $ nix-build '<nixpkgs>' -A libreoffice --argstr system x86_64-darwin
  error: the package ‘libreoffice-4.0.5.2’ in ‘.../applications/office/libreoffice/default.nix:263’
    is not supported on ‘x86_64-darwin’
  

• The garbage collector is now more concurrent with other Nix processes because it releases certain locks earlier.

• The binary tarball installer has been improved. You can now install Nix by running:

  $ bash <(curl -L https://nixos.org/nix/install)
  

• More evaluation errors include position information. For instance, selecting a missing attribute will print something like

  error: attribute `nixUnstabl' missing, at /etc/nixos/configurations/misc/eelco/mandark.nix:216:15
  

• The command nix-setuid-helper is gone.

• Nix no longer uses Automake, but instead has a non-recursive, GNU Make-based build system.

• All installed libraries now have the prefix libnix. In particular, this gets rid of libutil, which could clash with libraries with the same name from other packages.

• Nix now requires a compiler that supports C++11.

This release has contributions from Danny Wilson, Domen Kožar, Eelco Dolstra, Ian-Woo Kim, Ludovic Courtès, Maxim Ivanov, Petr Rockai, Ricardo M. Correia and Shea Levy.