159 lines
4.4 KiB
Perl
159 lines
4.4 KiB
Perl
use strict;
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use File::Find;
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use File::Copy;
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use File::Path;
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use File::Basename;
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use File::Slurp;
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my $etc = $ARGV[0] or die;
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my $static = "/etc/static";
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sub atomicSymlink {
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my ($source, $target) = @_;
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my $tmp = "$target.tmp";
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unlink $tmp;
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symlink $source, $tmp or return 0;
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if (rename $tmp, $target) {
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return 1;
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} else {
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unlink $tmp;
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return 0;
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}
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}
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# Atomically update /etc/static to point at the etc files of the
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# current configuration.
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atomicSymlink $etc, $static or die;
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# Returns 1 if the argument points to the files in /etc/static. That
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# means either argument is a symlink to a file in /etc/static or a
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# directory with all children being static.
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sub isStatic {
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my $path = shift;
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if (-l $path) {
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my $target = readlink $path;
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return substr($target, 0, length "/etc/static/") eq "/etc/static/";
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}
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if (-d $path) {
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opendir DIR, "$path" or return 0;
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my @names = readdir DIR or die;
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closedir DIR;
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foreach my $name (@names) {
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next if $name eq "." || $name eq "..";
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unless (isStatic("$path/$name")) {
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return 0;
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}
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}
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return 1;
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}
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return 0;
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}
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# Remove dangling symlinks that point to /etc/static. These are
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# configuration files that existed in a previous configuration but not
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# in the current one. For efficiency, don't look under /etc/nixos
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# (where all the NixOS sources live).
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sub cleanup {
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if ($File::Find::name eq "/etc/nixos") {
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$File::Find::prune = 1;
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return;
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}
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if (-l $_) {
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my $target = readlink $_;
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if (substr($target, 0, length $static) eq $static) {
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my $x = "/etc/static/" . substr($File::Find::name, length "/etc/");
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unless (-l $x) {
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print STDERR "removing obsolete symlink ‘$File::Find::name’...\n";
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unlink "$_";
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}
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}
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}
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}
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find(\&cleanup, "/etc");
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# Use /etc/.clean to keep track of copied files.
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my @oldCopied = read_file("/etc/.clean", chomp => 1, err_mode => 'quiet');
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open CLEAN, ">>/etc/.clean";
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# For every file in the etc tree, create a corresponding symlink in
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# /etc to /etc/static. The indirection through /etc/static is to make
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# switching to a new configuration somewhat more atomic.
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my %created;
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my @copied;
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sub link {
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my $fn = substr $File::Find::name, length($etc) + 1 or next;
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# nixos-enter sets up /etc/resolv.conf as a bind mount, so skip it.
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if ($fn eq "resolv.conf" and $ENV{'IN_NIXOS_ENTER'}) {
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return;
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}
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my $target = "/etc/$fn";
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File::Path::make_path(dirname $target);
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$created{$fn} = 1;
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# Rename doesn't work if target is directory.
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if (-l $_ && -d $target) {
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if (isStatic $target) {
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rmtree $target or warn;
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} else {
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warn "$target directory contains user files. Symlinking may fail.";
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}
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}
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if (-e "$_.mode") {
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my $mode = read_file("$_.mode"); chomp $mode;
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if ($mode eq "direct-symlink") {
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atomicSymlink readlink("$static/$fn"), $target or warn "could not create symlink $target";
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} else {
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my $uid = read_file("$_.uid"); chomp $uid;
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my $gid = read_file("$_.gid"); chomp $gid;
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copy "$static/$fn", "$target.tmp" or warn;
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$uid = getpwnam $uid unless $uid =~ /^\+/;
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$gid = getgrnam $gid unless $gid =~ /^\+/;
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chown int($uid), int($gid), "$target.tmp" or warn;
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chmod oct($mode), "$target.tmp" or warn;
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unless (rename "$target.tmp", $target) {
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warn "could not create target $target";
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unlink "$target.tmp";
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}
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}
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push @copied, $fn;
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print CLEAN "$fn\n";
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} elsif (-l "$_") {
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atomicSymlink "$static/$fn", $target or warn "could not create symlink $target";
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}
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}
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find(\&link, $etc);
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# Delete files that were copied in a previous version but not in the
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# current.
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foreach my $fn (@oldCopied) {
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if (!defined $created{$fn}) {
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$fn = "/etc/$fn";
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print STDERR "removing obsolete file ‘$fn’...\n";
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unlink "$fn";
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}
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}
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# Rewrite /etc/.clean.
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close CLEAN;
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write_file("/etc/.clean", map { "$_\n" } sort @copied);
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# Create /etc/NIXOS tag if not exists.
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# When /etc is not on a persistent filesystem, it will be wiped after reboot,
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# so we need to check and re-create it during activation.
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open TAG, ">>/etc/NIXOS";
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close TAG;
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