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use strict;
use File::Find;
use File::Copy;
use File::Path;
use File::Basename;
my $etc = $ARGV[0] or die;
my $static = "/etc/static";
sub atomicSymlink {
my ($source, $target) = @_;
my $tmp = "$target.tmp";
unlink $tmp;
symlink $source, $tmp or return 1;
rename $tmp, $target or return 1;
return 1;
}
# Atomically update /etc/static to point at the etc files of the
# current configuration.
atomicSymlink $etc, $static or die;
# Remove dangling symlinks that point to /etc/static. These are
# configuration files that existed in a previous configuration but not
# in the current one. For efficiency, don't look under /etc/nixos
# (where all the NixOS sources live).
sub cleanup {
if ($File::Find::name eq "/etc/nixos") {
$File::Find::prune = 1;
return;
}
if (-l $_) {
my $target = readlink $_;
if (substr($target, 0, length $static) eq $static) {
my $x = "/etc/static/" . substr($File::Find::name, length "/etc/");
unless (-l $x) {
print STDERR "removing obsolete symlink ‘$File::Find::name’...\n";
unlink "$_";
}
}
}
}
find(\&cleanup, "/etc");
# For every file in the etc tree, create a corresponding symlink in
# /etc to /etc/static. The indirection through /etc/static is to make
# switching to a new configuration somewhat more atomic.
sub link {
my $fn = substr $File::Find::name, length($etc) + 1 or next;
my $target = "/etc/$fn";
File::Path::make_path(dirname $target);
if (-e "$_.mode") {
open MODE, "<$_.mode";
my $mode = <MODE>; chomp $mode;
close MODE;
copy "$static/$fn", "$target.tmp" or warn;
chmod oct($mode), "$target.tmp" or warn;
rename "$target.tmp", $target or warn;
} elsif (-l "$_") {
atomicSymlink "$static/$fn", $target or warn;
}
}
find(\&link, $etc);
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