It moves runHook to a later position in the rcfile. After that we are
able to set the PS1 environment-variable for a nix-shell environment
e.g.:
# turn the color of the prompt to blue
shellHook = ''
export PS1="\n\[\033[1;34m\][\u@\h:\w]$\[\033[0m\] ";
'';
‘--run’ is like ‘--command’, except that it runs the command in a
non-interactive shell. This is important if you do things like:
$ nix-shell --command make
Hitting Ctrl-C while make is running drops you into the interactive
Nix shell, which is probably not what you want. So you can now do
$ nix-shell --run make
instead.
So you can have a script like:
#! /usr/bin/env nix-shell
#! nix-shell script.nix -i python
import prettytable
x = prettytable.PrettyTable(["Foo", "Bar"])
for i in range(1, 10): x.add_row([i, i**2])
print x
with a ‘script.nix’ in the same directory:
with import <nixpkgs> {};
runCommand "dummy" { buildInputs = [ python pythonPackages.prettytable ]; } ""
(Of course, in this particular case, using the ‘-p’ flag is more
convenient.)
This allows scripts to fetch their own dependencies via nix-shell. For
instance, here is a Haskell script that, when executed, pulls in GHC
and the HTTP package:
#! /usr/bin/env nix-shell
#! nix-shell -i runghc -p haskellPackages.ghc haskellPackages.HTTP
import Network.HTTP
main = do
resp <- Network.HTTP.simpleHTTP (getRequest "http://nixos.org/")
body <- getResponseBody resp
print (take 100 body)
Or a Perl script that pulls in Perl and some CPAN packages:
#! /usr/bin/env nix-shell
#! nix-shell -i perl -p perl perlPackages.HTMLTokeParserSimple perlPackages.LWP
use HTML::TokeParser::Simple;
my $p = HTML::TokeParser::Simple->new(url => 'http://nixos.org/');
while (my $token = $p->get_tag("a")) {
my $href = $token->get_attr("href");
print "$href\n" if $href;
}
Note that the options to nix-shell must be given on a separate line
that starts with the magic string ‘#! nix-shell’. This is because
‘env’ does not allow passing arguments to an interpreter directly.
Apparently, turning on utf8 encoding on stderr changes its flushing
behaviour, causing sendReply to not send anything.
http://hydra.nixos.org/build/13944384
This makes things more efficient (we don't need to use an SSH master
connection, and we only start a single remote process) and gets rid of
locking issues (the remote nix-store process will keep inputs and
outputs locked as long as they're needed).
It also makes it more or less secure to connect directly to the root
account on the build machine, using a forced command
(e.g. ‘command="nix-store --serve --write"’). This bypasses the Nix
daemon and is therefore more efficient.
Also, don't call nix-store to import the output paths.
If derivation declares multiple outputs and first (default) output
if not "out", then "nix-instantiate" calls return path with output
names appended after "!". Than suffix must be stripped before
ant path checks are done.
This allows you to easily set up a build environment containing the
specified packages from Nixpkgs. For example:
$ nix-shell -p sqlite xorg.libX11 hello
will start a shell in which the given packages are present.
The flag ‘--check’ to ‘nix-store -r’ or ‘nix-build’ will cause Nix to
redo the build of a derivation whose output paths are already valid.
If the new output differs from the original output, an error is
printed. This makes it easier to test if a build is deterministic.
(Obviously this cannot catch all sources of non-determinism, but it
catches the most common one, namely the current time.)
For example:
$ nix-build '<nixpkgs>' -A patchelf
...
$ nix-build '<nixpkgs>' -A patchelf --check
error: derivation `/nix/store/1ipvxsdnbhl1rw6siz6x92s7sc8nwkkb-patchelf-0.6' may not be deterministic: hash mismatch in output `/nix/store/4pc1dmw5xkwmc6q3gdc9i5nbjl4dkjpp-patchelf-0.6.drv'
The --check build fails if not all outputs are valid. Thus the first
call to nix-build is necessary to ensure that all outputs are valid.
The current outputs are left untouched: the new outputs are either put
in a chroot or diverted to a different location in the store using
hash rewriting.
The tarball can now be unpacked anywhere. The installation script
uses "sudo" to create /nix if it doesn't exist. It also fetches the
nixpkgs-unstable channel.
NAR info files in binary caches can now have a cryptographic signature
that Nix will verify before using the corresponding NAR file.
To create a private/public key pair for signing and verifying a binary
cache, do:
$ openssl genrsa -out ./cache-key.sec 2048
$ openssl rsa -in ./cache-key.sec -pubout > ./cache-key.pub
You should also come up with a symbolic name for the key, such as
"cache.example.org-1". This will be used by clients to look up the
public key. (It's a good idea to number keys, in case you ever need
to revoke/replace one.)
To create a binary cache signed with the private key:
$ nix-push --dest /path/to/binary-cache --key ./cache-key.sec --key-name cache.example.org-1
The public key (cache-key.pub) should be distributed to the clients.
They should have a nix.conf should contain something like:
signed-binary-caches = *
binary-cache-public-key-cache.example.org-1 = /path/to/cache-key.pub
If all works well, then if Nix fetches something from the signed
binary cache, you will see a message like:
*** Downloading ‘http://cache.example.org/nar/7dppcj5sc1nda7l54rjc0g5l1hamj09j-subversion-1.7.11’ (signed by ‘cache.example.org-1’) to ‘/nix/store/7dppcj5sc1nda7l54rjc0g5l1hamj09j-subversion-1.7.11’...
On the other hand, if the signature is wrong, you get a message like
NAR info file `http://cache.example.org/7dppcj5sc1nda7l54rjc0g5l1hamj09j.narinfo' has an invalid signature; ignoring
Signatures are implemented as a single line appended to the NAR info
file, which looks like this:
Signature: 1;cache.example.org-1;HQ9Xzyanq9iV...muQ==
Thus the signature has 3 fields: a version (currently "1"), the ID of
key, and the base64-encoded signature of the SHA-256 hash of the
contents of the NAR info file up to but not including the Signature
line.
Issue #75.
This reverts commit 194e3374b8.
Checking the command line for GC roots means that
$ nix-store --delete $path
will fail because $path is now a root because it's mentioned on the
command line.
