Nix Release 1.9: Continued Chroot, Evaluation, and Usability Enhancements

print (take 100 body) Of course, the dependencies are cached in the Nix store, so the second invocation of this script will be much faster. - Chroot improvements: - Chroot builds are now supported on Mac OS X (using its sandbox mechanism). - If chroots are enabled, they are now used for all derivations, including fixed-output derivations (such as `fetchurl`). The latter do have network access, but can no longer access the host filesystem. If you need the old behaviour, you can set the option `build-use-chroot` to `relaxed`. - On Linux, if chroots are enabled, builds are performed in a private PID namespace once again. (This functionality was lost in Nix 1.8.) - Store paths listed in `build-chroot-dirs` are now automatically expanded to their closure. For instance, if you want `/nix/store/…-bash/bin/sh` mounted in your chroot as `/bin/sh`, you only need to say `build-chroot-dirs = /bin/sh=/nix/store/…-bash/bin/sh`; it is no longer necessary to specify the dependencies of Bash. - The new derivation attribute `passAsFile` allows you to specify that the contents of derivation attributes should be passed via files rather than environment variables. This is useful if you need to pass very long strings that exceed the size limit of the environment. The Nixpkgs function `writeTextFile` uses this. - You can now use `~` in Nix file names to refer to your home directory, e.g. `import ~/.nixpkgs/config.nix`. - Nix has a new option `restrict-eval` that allows limiting what paths the Nix evaluator has access to. By passing `--option restrict-eval true` to Nix, the evaluator will throw an exception if an attempt is made to access any file outside of the Nix search path. This is primarily intended for Hydra to ensure that a Hydra jobset only refers to its declared inputs (and is therefore reproducible). - `nix-env` now only creates a new “generation” symlink in `/nix/var/nix/profiles` if something actually changed. - The environment variable `NIX_PAGER` can now be set to override `PAGER`. You can set it to `cat` to disable paging for Nix commands only. - Failing `<...>` lookups now show position information. - Improved Boehm GC use: we disabled scanning for interior pointers, which should reduce the “`Repeated allocation of very large block`” warnings and associated retention of memory. This release has contributions from aszlig, Benjamin Staffin, Charles Strahan, Christian Theune, Daniel Hahler, Danylo Hlynskyi Daniel Peebles, Dan Peebles, Domen Kožar, Eelco Dolstra, Harald van Dijk, Hoang Xuan Phu, Jaka Hudoklin, Jeff Ramnani, j-keck, Linquize, Luca Bruno, Michael Merickel, Oliver Dunkl, Rob Vermaas, Rok Garbas, Shea Levy, Tobias Geerinckx-Rice and William A. Kennington III.

This chunk details additional improvements in Nix Release 1.9. Chroot functionality sees further enhancements, including Mac OS X support, application to all derivations by default (with a `relaxed` option for older behavior), restored private PID namespaces on Linux, and automatic expansion of `build-chroot-dirs` paths. New features include the `passAsFile` derivation attribute for handling long strings, support for `~` in Nix file paths, and a `restrict-eval` option to limit file access during evaluation for reproducibility. Usability improvements cover `nix-env` only creating new generations on actual changes, a `NIX_PAGER` environment variable, better error reporting for `<...>` lookups, and optimized Boehm GC use. The chunk concludes with a list of contributors to this release.