a user environment by an install or upgrade action. This is
particularly useful if you have a version installed that you don't
want to upgrade (e.g., because the newer versions are broken).
Example:
$ nix-env -u zapping --dry-run
(dry run; not doing anything)
upgrading `zapping-0.9.6' to `zapping-0.10cvs6'
$ nix-env --set-flag keep true zapping
$ nix-env -u zapping --dry-run
(dry run; not doing anything)
However, "-e" will still uninstall the package. (Maybe we should
require the keep flag to be explicitly set to false before it can be
uninstalled.)
user environment collission between two packages due to overlapping
file names, then a package with a higher priority will overwrite the
symlinks of a package with a lower priority. E.g.,
$ nix-env --set-flag priority 5 gcc
$ nix-env --set-flag priority 10 binutils
gives gcc a higher priority than binutils (higher number = lower
priority).
allow switching between them (NIX-80).
Example: two versions of Pan:
$ nix-env -q pan
pan-0.128
pan-0.14.2.91
$ readlink $(which pan)
/nix/store/l38jrbilw269drpjkx7kinhrxj6fjh59-pan-0.14.2.91/bin/pan
At most one of them can be active any given time. Assuming than
0.14.2.91 is active, you can active 0.128 as follows:
$ nix-env --set-flag active false pan-0.14.2.91
$ nix-env --set-flag active true pan-0.128
$ readlink $(which pan)
/nix/store/nziqwnlzy7xl385kglxhg75pfl5i936n-pan-0.128/bin/pan
More flags to follow.
to show only those derivations whose output is already in the Nix
store or that can be substituted (i.e., downloaded from somewhere).
In other words, it shows the packages that can be installed “quickly”,
i.e., don’t need to be built from source.
evaluator. This was important because the NixOS expressions started
to hit 2 MB default stack size on Linux.
GCC is really dumb about stack space: it just adds up all the local
variables and temporaries of every scope into one huge stack frame.
This is really bad for deeply recursive functions. For instance,
every `throw Error(format("error message"))' causes a format object
of a few hundred bytes to be allocated on the stack. As a result,
every recursive call to evalExpr2() consumed 4680 bytes. By
splitting evalExpr2() and by moving the exception-throwing code out
of the main functions, evalExpr2() now only consumes 40 bytes.
Similar for evalExpr().
another machine through ssh. E.g.,
$ nix-copy-closure xyzzy $(which svn)
copies the closure of Subversion to machine `xyzzy'. This is like
`nix-pack-closure $(which svn) | ssh xyzzy', but it's much more
efficient since it only copies those paths that are missing on the
target machine.
which paths specified on the command line are invalid (i.e., don't
barf when encountering an invalid path, just print it). This is
useful for build-remote.pl to figure out which paths need to be
copied to a remote machine. (Currently we use rsync, but that's
rather inefficient.)
--export' into the Nix store, and optionally check the cryptographic
signatures against /nix/etc/nix/signing-key.pub. (TODO: verify
against a set of public keys.)
path. This is like `nix-store --dump', only it also dumps the
meta-information of the store path (references, deriver). Will add
a `--sign' flag later to add a cryptographic signature, which we
will use for exchanging store paths between build farm machines in a
secure manner.
