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nixos/systemd|filesystems: mount and evacuate /sys/fs/pstore using systemd-pstore #85073

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Merged
flokli merged 2 commits into from May 16, 2021
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nixos/systemd|filesystems: mount and evacuate /sys/fs/pstore using systemd-pstore #85073

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870fa77
nixos/filesystems: mount persistent storage to /sys/fs/pstore
Dec 1, 2020
3e3e763
nixos/systemd: enable systemd-pstore.service
Dec 1, 2020
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6 changes: 6 additions & 0 deletions nixos/doc/manual/release-notes/rl-2105.xml
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Expand Up @@ -1035,6 +1035,12 @@ environment.systemPackages = [
</programlisting>
</para>
</listitem>
<listitem>
<para>
The newly enabled <literal>systemd-pstore.service</literal> now automatically evacuates crashdumps and panic logs from the persistent storage to <literal>/var/lib/systemd/pstore</literal>.
This prevents NVRAM from filling up, which ensures the latest diagnostic data is always stored and alleviates problems with writing new boot configurations.
</para>
</listitem>
</itemizedlist>
</section>
</section>
8 changes: 8 additions & 0 deletions nixos/modules/profiles/installation-device.nix
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Expand Up @@ -99,5 +99,13 @@ with lib;
# because we have the firewall enabled. This makes installs from the
# console less cumbersome if the machine has a public IP.
networking.firewall.logRefusedConnections = mkDefault false;

# Prevent installation media from evacuating persistent storage, as their
# var directory is not persistent and it would thus result in deletion of
# those entries.
environment.etc."systemd/pstore.conf".text = ''
[PStore]
Unlink=no
'';
};
}
2 changes: 2 additions & 0 deletions nixos/modules/system/boot/systemd.nix
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Expand Up @@ -90,6 +90,7 @@ let
"systemd-fsck@.service"
"systemd-fsck-root.service"
"systemd-remount-fs.service"
"systemd-pstore.service"
"local-fs.target"
"local-fs-pre.target"
"remote-fs.target"
Expand Down Expand Up @@ -1183,6 +1184,7 @@ in
systemd.targets.remote-fs.unitConfig.X-StopOnReconfiguration = true;
systemd.targets.network-online.wantedBy = [ "multi-user.target" ];
systemd.services.systemd-importd.environment = proxy_env;
systemd.services.systemd-pstore.wantedBy = [ "sysinit.target" ]; # see #81138

# Don't bother with certain units in containers.
systemd.services.systemd-remount-fs.unitConfig.ConditionVirtualization = "!container";
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34 changes: 30 additions & 4 deletions nixos/modules/tasks/filesystems.nix
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Expand Up @@ -272,10 +272,10 @@ in
wants = [ "local-fs.target" "remote-fs.target" ];
};

# Emit systemd services to format requested filesystems.
systemd.services =
let

# Emit systemd services to format requested filesystems.
let
formatDevice = fs:
let
mountPoint' = "${escapeSystemdPath fs.mountPoint}.mount";
Expand All @@ -302,8 +302,34 @@ in
unitConfig.DefaultDependencies = false; # needed to prevent a cycle
serviceConfig.Type = "oneshot";
};

in listToAttrs (map formatDevice (filter (fs: fs.autoFormat) fileSystems));
in listToAttrs (map formatDevice (filter (fs: fs.autoFormat) fileSystems)) // {
# Mount /sys/fs/pstore for evacuating panic logs and crashdumps from persistent storage onto the disk using systemd-pstore.
# This cannot be done with the other special filesystems because the pstore module (which creates the mount point) is not loaded then.
# Since the pstore filesystem is usually empty right after mounting because the backend isn't registered yet, and a path unit cannot detect files inside of it, the same service waits for that to happen. systemd's restart mechanism can't be used here because the first failure also fails all dependent units.
"mount-pstore" = {
serviceConfig = {
Type = "oneshot";
ExecStart = "${pkgs.utillinux}/bin/mount -t pstore -o nosuid,noexec,nodev pstore /sys/fs/pstore";
ExecStartPost = pkgs.writeShellScript "wait-for-pstore.sh" ''
set -eu
TRIES=0
while [ $TRIES -lt 20 ] && [ "$(cat /sys/module/pstore/parameters/backend)" = "(null)" ]; do
sleep 0.1
TRIES=$((TRIES+1))
done
'';
RemainAfterExit = true;
};
unitConfig = {
ConditionVirtualization = "!container";
DefaultDependencies = false; # needed to prevent a cycle
};
after = [ "modprobe@pstore.service" ];
requires = [ "modprobe@pstore.service" ];
before = [ "systemd-pstore.service" ];
wantedBy = [ "systemd-pstore.service" ];
};
};

systemd.tmpfiles.rules = [
"d /run/keys 0750 root ${toString config.ids.gids.keys}"
Expand Down