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For some units, use "systemctl restart" rather than "systemctl stop/start"

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During a configuration switch, changed units are stopped in the old
configuration, then started in the new configuration (i.e. after
running the activation script and running "systemctl daemon-reload").
This ensures that services are stopped using the ExecStop/ExecStopPost
commands from the old configuration.

However, for some services it's undesirable to stop them; in
particular dhcpcd, which deconfigures its network interfaces when it
stops.  This is dangerous when doing remote upgrades - usually things
go right (especially because the switch script ignores SIGHUP), but
not always (see 9aa69885f0).  Likewise,
sshd should be kept running for as long as possible to prevent a
lock-out if the switch fails.

So the new option ‘stopIfChanged = false’ causes "systemctl restart"
to be used instead of "systemctl stop" followed by "systemctl start".
This is only proper for services that don't have stop commands.  (And
it might not handle dependencies properly in some cases, but I'm not
sure.)
This commit is contained in:
Eelco Dolstra 2013-01-05 01:05:25 +01:00
parent baac242a1f
commit 96ba0ca283
5 changed files with 56 additions and 13 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
modules/services/networking/dhcpcd.nix
View file

@ -97,6 +97,11 @@ in
wantedBy = [ "network.target" ];
# Stopping dhcpcd during a reconfiguration is undesirable
# because it brings down the network interfaces configured by
# dhcpcd. So do a "systemctl restart" instead.
stopIfChanged = false;
path = [ dhcpcd pkgs.nettools pkgs.openresolv ];
serviceConfig =

2
modules/services/networking/ssh/sshd.nix
View file

@ -267,6 +267,8 @@ in
wantedBy = [ "multi-user.target" ];
stopIfChanged = false;
path = [ pkgs.openssh ];
environment.LD_LIBRARY_PATH = nssModulesPath;

46
modules/system/activation/switch-to-configuration.pl
View file

@ -6,6 +6,7 @@ use File::Basename;
use File::Slurp;
use Cwd 'abs_path';
my $startListFile = "/run/systemd/start-list";
my $restartListFile = "/run/systemd/restart-list";
my $reloadListFile = "/run/systemd/reload-list";
@ -125,7 +126,7 @@ while (my ($unit, $state) = each %{$activePrev}) {
if ($unit ne "suspend.target" && $unit ne "hibernate.target") {
my $unitInfo = parseUnit($newUnitFile);
unless (boolIsTrue($unitInfo->{'RefuseManualStart'} // "false")) {
write_file($restartListFile, { append => 1 }, "$unit\n");
write_file($startListFile, { append => 1 }, "$unit\n");
}
}
}
@ -158,21 +159,31 @@ while (my ($unit, $state) = each %{$activePrev}) {
foreach my $socket (@sockets) {
if (defined $activePrev->{$socket}) {
push @unitsToStop, $socket;
write_file($restartListFile, { append => 1 }, "$socket\n");
write_file($startListFile, { append => 1 }, "$socket\n");
$socketActivated = 1;
}
}
}
# Otherwise, record that this unit needs to be
# started below. We write this to a file to
# ensure that the service gets restarted if we're
# interrupted.
if (!$socketActivated) {
write_file($restartListFile, { append => 1 }, "$unit\n");
}
if (!boolIsTrue($unitInfo->{'X-StopIfChanged'} // "true")) {
push @unitsToStop, $unit;
# This unit should be restarted instead of
# stopped and started.
write_file($restartListFile, { append => 1 }, "$unit\n");
} else {
# If the unit is not socket-activated, record
# that this unit needs to be started below.
# We write this to a file to ensure that the
# service gets restarted if we're interrupted.
if (!$socketActivated) {
write_file($startListFile, { append => 1 }, "$unit\n");
}
push @unitsToStop, $unit;
}
}
}
}
@ -216,7 +227,7 @@ foreach my $mountPoint (keys %$prevFss) {
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 }, "$unit\n");
write_file($startListFile, { append => 1 }, "$unit\n");
push @unitsToStop, $unit;
} elsif ($prev->{options} ne $new->{options}) {
# Mount options changes, so remount it.
@ -266,16 +277,25 @@ system("@systemd@/bin/systemctl", "reset-failed");
# Make systemd reload its units.
system("@systemd@/bin/systemctl", "daemon-reload") == 0 or $res = 3;
# Restart changed services (those that have to be restarted rather
# than stopped and started).
my @restart = unique(split('\n', read_file($restartListFile, err_mode => 'quiet') // ""));
if (scalar @restart > 0) {
print STDERR "restarting the following units: ", join(", ", sort(@restart)), "\n";
system("@systemd@/bin/systemctl", "restart", "--", @restart) == 0 or $res = 4;
unlink($restartListFile);
}
# Start all active targets, as well as changed units we stopped above.
# The latter is necessary because some may not be dependencies of the
# targets (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", split('\n', read_file($restartListFile, err_mode => 'quiet') // ""));
my @start = unique("default.target", split('\n', read_file($startListFile, err_mode => 'quiet') // ""));
print STDERR "starting the following units: ", join(", ", sort(@start)), "\n";
system("@systemd@/bin/systemctl", "start", "--", @start) == 0 or $res = 4;
unlink($restartListFile);
unlink($startListFile);
# Reload units that need it. This includes remounting changed mount
# units.

15
modules/system/boot/systemd-unit-options.nix
View file

@ -183,6 +183,21 @@ rec {
'';
};
stopIfChanged = mkOption {
type = types.bool;
default = true;
description = ''
If set, a changed unit is restarted by calling
<command>systemctl stop</command> in the old configuration,
then <command>systemctl start</command> in the new one.
Otherwise, it is restarted in a single step using
<command>systemctl restart</command> in the new configuration.
The latter is less correct because it runs the
<literal>ExecStop</literal> commands from the new
configuration.
'';
};
};

1
modules/system/boot/systemd.nix
View file

@ -246,6 +246,7 @@ let
${let env = cfg.globalEnvironment // def.environment;
in concatMapStrings (n: "Environment=${n}=${getAttr n env}\n") (attrNames env)}
${optionalString (!def.restartIfChanged) "X-RestartIfChanged=false"}
${optionalString (!def.stopIfChanged) "X-StopIfChanged=false"}
${optionalString (def.preStart != "") ''
ExecStartPre=${makeJobScript "${name}-pre-start" ''