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* The policy-free derivate sharing now *almost* works. :-) For any

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hash for which no local expansion is available, Nix can execute a
  `substitute' which should produce a path with such a hash.

  This is policy-free since Nix does not in any way specify how the
  substitute should work, i.e., it's an arbitrary (unnormalised)
  fstate expression.  For example, `nix-pull' registers substitutes
  that fetch Nix archives from the network (through `wget') and unpack
  them, but any other method is possible as well.  This is an
  improvement over the old Nix sharing scheme, which had a policy
  (fetching through `wget') built in.

  The sharing scheme doesn't work completely yet because successors
  from fstate rewriting have to be registered on the receiving side.
  Probably the whole successor stuff can be folded up into the
  substitute mechanism; this would be a nice simplification.
This commit is contained in:
Eelco Dolstra 2003-07-10 15:11:48 +00:00
parent d072485d28
commit 1d1c3691d2
13 changed files with 155 additions and 142 deletions
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65
scripts/nix-pull
View file

@ -1,2 +1,67 @@
#! /usr/bin/perl -w
my $prefix = $ENV{"NIX"} || "/tmp/nix"; # !!! use prefix
my $etcdir = "$prefix/etc/nix";
my $tmpfile = "$prefix/var/nix/pull.tmp";
my $conffile = "$etcdir/prebuilts.conf";
open CONFFILE, "<$conffile";
while (<CONFFILE>) {
chomp;
if (/^\s*(\S+)\s*(\#.*)?$/) {
my $url = $1;
print "obtaining list of Nix archives at $url...\n";
system "wget '$url' -O '$tmpfile' 2> /dev/null"; # !!! escape
if ($?) { die "`wget' failed"; }
open INDEX, "<$tmpfile";
while (<INDEX>) {
# Get all links to prebuilts, that is, file names of the
# form foo-HASH-HASH.tar.bz2.
next unless (/HREF=\"([^\"]*)\"/);
my $fn = $1;
next if $fn =~ /\.\./;
next if $fn =~ /\//;
next unless $fn =~ /([0-9a-z]{32})-([0-9a-z]{32})\.nar/;
my $hash = $2;
print "registering $hash -> $url/$fn\n";
# Construct a Fix expression that fetches and unpacks a
# Nix archive from the network.
my $fetch =
"App(IncludeFix(\"fetchurl/fetchurl.fix\"), " .
"[(\"url\", \"$url/$fn\"), (\"hash\", \"\")])";
my $fixexpr =
"App(IncludeFix(\"nar/unnar.fix\"), " .
"[ (\"nar\", $fetch)" .
", (\"name\", \"fetched-$hash\")" .
"])";
my $fixfile = "/tmp/nix-pull-tmp.fix";
open FIX, ">$fixfile";
print FIX $fixexpr;
close FIX;
# Instantiate a Nix expression from the Fix expression.
my $nhash = `fix $fixfile`;
$? and die "instantiating Nix archive expression";
chomp $nhash;
die unless $nhash =~ /^([0-9a-z]{32})$/;
system "nix --substitute $hash $nhash";
if ($?) { die "`nix --substitute' failed"; }
}
close INDEX;
unlink $tmpfile;
}
}