dependency. `storePath /nix/store/bla' gives exactly the same
result as `toPath /nix/store/bla', except that the former includes
/nix/store/bla in the dependency context of the string.
Useful in some generated Nix expressions like nix-push, which now
finally does the right thing wrt distributed builds. (Previously
the path to be packed wasn't an explicit dependency, so it wouldn't
be copied to the remote machine.)
subtle and often hard-to-reproduce bugs where programs in pipes
either barf with a "Broken pipe" message or not, depending on the
exact timing conditions. This particularly happened in GNU M4 (and
Bison, which uses M4).
disasters involving `rm -rf' on bind mounts. Will try the
definitive fix (per-process mounts, apparently possible via the
CLONE_NEWNS flag in clone()) some other time.
accessed time of paths that may be deleted. Anything more recently
used won't be deleted. The time is specified in time_t,
e.g. seconds since 1970-01-01 00:00:00 UTC; use `date +%s' to
convert to time_t from the command line.
Example: to delete everything that hasn't been used in the last two
months:
$ nix-store --gc -v --max-atime $(date +%s -d "2 months ago")
order of ascending last access time. This is useful in conjunction
with --max-freed or --max-links to prefer deleting non-recently used
garbage, which is good (especially in the build farm) since garbage
may become live again.
The code could easily be modified to accept other criteria for
ordering garbage by changing the comparison operator used by the
priority queue in collectGarbage().
attributes from the meta attribute. Not doing so caused nix-env to
barf on the "psi" package, which has a meta.function attribute,
the textual serialisation of which causes a gigantic string to be
produced --- so big that it causes nix-env to run out of memory.
Note however that "meta" really only should contain strings.
meta.function should be passthru.function.
particular, dietlibc cannot figure out the cwd because the inode of
the current directory doesn't appear in .. (because getdents returns
the inode of the mount point).
(which means it can only be defined via "inherit"), otherwise we get
scoping bugs, since __overrides can't be recursive (or at least, it
would be hard).
need /etc in the chroot (in particular, /etc/resolv.conf for
fetchurl). Not having /etc/resolv.conf in the chroot is a good
thing, since we don't want normal derivations to download files.
~/.nix-defexpr, otherwise the attribute cannot be selected with the
`-A' option. Useful if you want to stick a Nix expression directly
in ~/.nix-defexpr.
a rec. This will be very useful to allow end-user customisation of
all-packages.nix, for instance globally overriding GCC or some other
dependency. The // operator doesn't cut it: you could replace the
"gcc" attribute, but all other attributes would continue to
reference the original value due to the substitution semantics of
rec.
The syntax is a bit hacky but this is to allow backwards
compatibility.
in attribute set pattern matches. This allows defining a function
that takes *at least* the listed attributes, while ignoring
additional attributes. For instance,
{stdenv, fetchurl, fuse, ...}:
stdenv.mkDerivation {
...
};
defines a function that requires an attribute set that contains the
specified attributes but ignores others. The main advantage is that
we can then write in all-packages.nix
aefs = import ../bla/aefs pkgs;
instead of
aefs = import ../bla/aefs {
inherit stdenv fetchurl fuse;
};
This saves a lot of typing (not to mention not having to update
all-packages.nix with purely mechanical changes). It saves as much
typing as the "args: with args;" style, but has the advantage that
the function arguments are properly declared (not implicit in what
the body of the "with" uses).
