nixpkgs/modules/system/activation/switch-to-configuration.pl

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#! @perl@
use strict;
use warnings;
use File::Basename;
use File::Slurp;
use Cwd 'abs_path';
my $restartListFile = "/run/systemd/restart-list";
my $reloadListFile = "/run/systemd/reload-list";
my $action = shift @ARGV;
if (!defined $action || ($action ne "switch" && $action ne "boot" && $action ne "test")) {
print STDERR <<EOF;
Usage: $0 [switch|boot|test]
switch: make the configuration the boot default and activate now
boot: make the configuration the boot default
test: activate the configuration, but don\'t make it the boot default
EOF
exit 1;
}
die "This is not a NixOS installation (/etc/NIXOS is missing)!\n" unless -f "/etc/NIXOS";
# Install or update the bootloader.
if ($action eq "switch" || $action eq "boot") {
system("@installBootLoader@ @out@") == 0 or exit 1;
exit 0 if $action eq "boot";
}
# Check if we can activate the new configuration.
my $oldVersion = read_file("/run/current-system/init-interface-version", err_mode => 'quiet') // "";
my $newVersion = read_file("@out@/init-interface-version");
if ($newVersion ne $oldVersion) {
print STDERR <<EOF;
Warning: the new NixOS configuration has an init that is
incompatible with the current configuration. The new configuration
won\'t take effect until you reboot the system.
EOF
exit 100;
}
# Ignore SIGHUP so that we're not killed if we're running on (say)
# virtual console 1 and we restart the "tty1" unit.
$SIG{PIPE} = "IGNORE";
sub getActiveUnits {
# FIXME: use D-Bus or whatever to query this, since parsing the
# output of list-units is likely to break.
my $lines = `@systemd@/bin/systemctl list-units --full`;
my $res = {};
foreach my $line (split '\n', $lines) {
chomp $line;
last if $line eq "";
$line =~ /^(\S+)\s+(\S+)\s+(\S+)\s+(\S+)\s/ or next;
next if $1 eq "UNIT";
$res->{$1} = { load => $2, state => $3, substate => $4 };
}
return $res;
}
sub parseFstab {
my ($filename) = @_;
my %res;
foreach my $line (read_file($filename, err_mode => 'quiet')) {
chomp $line;
$line =~ s/#.*//;
next if $line =~ /^\s*$/;
my @xs = split / /, $line;
$res{$xs[1]} = { device => $xs[0], fsType => $xs[2], options => $xs[3] // "" };
}
return %res;
}
# Forget about previously failed services.
system("@systemd@/bin/systemctl", "reset-failed");
# Stop all services that no longer exist or have changed in the new
# configuration.
my @unitsToStop;
my $activePrev = getActiveUnits;
while (my ($unit, $state) = each %{$activePrev}) {
my $baseUnit = $unit;
# Recognise template instances.
$baseUnit = "$1\@.$2" if $unit =~ /^(.*)@[^\.]*\.(.*)$/;
my $prevUnitFile = "/etc/systemd/system/$baseUnit";
my $newUnitFile = "@out@/etc/systemd/system/$baseUnit";
if (-e $prevUnitFile && ($state->{state} eq "active" || $state->{state} eq "activating")) {
if (! -e $newUnitFile) {
push @unitsToStop, $unit;
} elsif (abs_path($prevUnitFile) ne abs_path($newUnitFile)) {
if ($unit eq "sysinit.target" || $unit eq "basic.target" || $unit eq "multi-user.target" || $unit eq "graphical.target") {
# Do nothing. These cannot be restarted directly.
} elsif ($unit =~ /\.target$/) {
write_file($restartListFile, { append => 1 }, "$unit\n");
} elsif ($unit =~ /\.mount$/) {
# Reload the changed mount unit to force a remount.
write_file($reloadListFile, { append => 1 }, "$unit\n");
} elsif ($unit =~ /\.socket$/ || $unit =~ /\.path$/) {
# FIXME: do something?
} else {
# Record that this unit needs to be started below. We
# write this to a file to ensure that the service gets
# restarted if we're interrupted.
write_file($restartListFile, { append => 1 }, "$unit\n");
push @unitsToStop, $unit;
}
}
}
}
sub pathToUnitName {
my ($path) = @_;
die unless substr($path, 0, 1) eq "/";
return "-" if $path eq "/";
$path = substr($path, 1);
$path =~ s/\//-/g;
# FIXME: handle - and unprintable characters.
return $path;
}
# Compare the previous and new fstab to figure out which filesystems
# need a remount or need to be unmounted. New filesystems are mounted
# automatically by starting local-fs.target. Also handles swap
# devices. FIXME: might be nicer if we generated units for all
# mounts; then we could unify this with the unit checking code above.
my %prevFstab = parseFstab "/etc/fstab";
my %newFstab = parseFstab "@out@/etc/fstab";
foreach my $mountPoint (keys %prevFstab) {
my $prev = $prevFstab{$mountPoint};
my $new = $newFstab{$mountPoint};
my $unit = pathToUnitName($mountPoint). ".mount" if $prev->{fsType} ne "swap";
if (!defined $new) {
if ($prev->{fsType} eq "swap") {
# Swap entry disappeared, so turn it off. Can't use
# "systemctl stop" here because systemd has lots of alias
# units that prevent a stop from actually calling
# "swapoff".
system("@utillinux@/sbin/swapoff", $prev->{device});
} else {
# Filesystem entry disappeared, so unmount it.
push @unitsToStop, $unit;
}
} elsif ($prev->{fsType} ne $new->{fsType} || $prev->{device} ne $new->{device}) {
# Filesystem type or device changed, so unmount and mount it.
write_file($restartListFile, { append => 1 }, "$unit\n");
push @unitsToStop, $unit;
} elsif ($prev->{options} ne $new->{options}) {
# Mount options changes, so remount it.
write_file($reloadListFile, { append => 1 }, "$unit\n");
}
}
if (scalar @unitsToStop > 0) {
print STDERR "stopping the following units: ", join(", ", sort(@unitsToStop)), "\n";
system("@systemd@/bin/systemctl", "stop", "--", @unitsToStop); # FIXME: ignore errors?
}
# Activate the new configuration (i.e., update /etc, make accounts,
# and so on).
my $res = 0;
print STDERR "activating the configuration...\n";
system("@out@/activate", "@out@") == 0 or $res = 2;
# FIXME: Re-exec systemd if necessary.
# Make systemd reload its units.
system("@systemd@/bin/systemctl", "daemon-reload") == 0 or $res = 3;
sub unique {
my %unique = map { $_, 1 } @_;
return sort(keys(%unique));
}
# Start the following units:
# - The default target. This should start most changed units we
# stopped above as well as any new dependencies.
# - local-fs.target. This mounts any missing local filesystems.
# - Changed units we stopped above. This is necessary because some
# may not be dependencies of the default target (i.e., they were
# manually started).
# FIXME: detect units that are symlinks to other units. We shouldn't
# start both at the same time because we'll get a "Failed to add path
# to set" error from systemd.
my @start = unique(
"default.target", "local-fs.target", "swap.target",
split('\n', read_file($restartListFile, err_mode => 'quiet') // ""));
print STDERR "starting the following units: ", join(", ", @start), "\n";
system("@systemd@/bin/systemctl", "start", "--", @start) == 0 or $res = 4;
unlink($restartListFile);
# Reload units that need it. This includes remounting changed mount
# units.
my @reload = unique(split '\n', read_file($reloadListFile, err_mode => 'quiet') // "");
if (scalar @reload > 0) {
print STDERR "reloading the following units: ", join(", ", @reload), "\n";
system("@systemd@/bin/systemctl", "reload", "--", @reload) == 0 or $res = 4;
unlink($reloadListFile);
}
# Signal dbus to reload its configuration.
system("@systemd@/bin/systemctl", "reload", "dbus.service");
# Print failed and new units.
my (@failed, @new, @restarting);
my $activeNew = getActiveUnits;
while (my ($unit, $state) = each %{$activeNew}) {
push @failed, $unit if $state->{state} eq "failed" || $state->{substate} eq "auto-restart";
push @new, $unit if $state->{state} ne "failed" && !defined $activePrev->{$unit};
}
print STDERR "the following new units were started: ", join(", ", sort(@new)), "\n"
if scalar @new > 0;
if (scalar @failed > 0) {
print STDERR "warning: the following units failed: ", join(", ", sort(@failed)), "\n";
foreach my $unit (@failed) {
print STDERR "\n";
system("COLUMNS=1000 @systemd@/bin/systemctl status --no-pager '$unit' >&2");
}
$res = 4;
}
exit $res;