This should make /home as automount work reasonably well.
If /home is an automount this has little effect at boot, because if the
automount is not triggered it doesn't matter how the associated mount is
ordered.
It does matter at shutdown however, where home.mount is likely active
now. There the ordering means we'll end sessions first, and only then
deactivate home.mount.
Fixes: #16291
Combining Requires= with Before= doesn't really make sense, since this
means we are requiring something that runs after us, which logically
cannot be fulfilled.
Let's hence downgrade Requires= to Wants= so that the ordering is kept
but no failure propagation implied.
This should be enough to fix https://bugzilla.redhat.com/show_bug.cgi?id=1856514.
But the limit should be significantly higher than 10% anyway. By setting a
limit on /tmp at 10% we'll break many reasonable use cases, even though the
machine would deal fine with a much larger fraction devoted to /tmp.
(In the first version of this patch I made it 25% with the comment that
"Even 25% might be too low.". The kernel default is 50%, and we have been using
that seemingly without trouble since https://fedoraproject.org/wiki/Features/tmp-on-tmpfs.
So let's just make it 50% again.)
See 7d85383edb.
(Another consideration is that we learned from from the whole initiative with
zram in Fedora that a reasonable size for zram is 0.5-1.5 of RAM, and that pretty
much all systems benefit from having zram or zswap enabled. Thus it is reasonable
to assume that it'll become widely used. Taking the usual compression effectiveness
of 0.2 into account, machines have effective memory available of between
1.0 - 0.2*0.5 + 0.5 = 1.4 (for zram sized to 0.5 of RAM) and
1.0 - 0.2*1.5 + 1.5 = 2.2 (for zram 1.5 sized to 1.5 of RAM) times RAM size.
This means that the 10% was really like 7-4% of effective memory.)
A comment is added to mount-util.h to clarify that tmp.mount is separate.
This reverts commit c7220ca802.
The removal was done as a reaction to the messages from systemd:
initrd-root-fs.target: Requested dependency OnFailure=emergency.target ignored (target units cannot fail).
initrd.target: Requested dependency OnFailure=emergency.target ignored (target units cannot fail).
initrd-root-device.target: Requested dependency OnFailure=emergency.target ignored (target units cannot fail).
initrd-fs.target: Requested dependency OnFailure=emergency.target ignored (target units cannot fail).
local-fs.target: Requested dependency OnFailure=emergency.target ignored (target units cannot fail).
...
But it seems that the messages themselves are wrong, and the units were OK.
Strictly speaking you can run homed without userdb. But it doesn't
really make much sense: they go hand in hand and implement the same
concepts, just for different sets of users. Let's hence disable both
automatically by default if homed is requested.
(We don't do the reverse: opting into userdbd shouldn't mean that you
are OK with homed.)
And of course, users can always deviate from our defaults easily, and
turn off userbd again right-away if they don't like it, and things will
generally work.
This generator can be used by desktop environments to launch autostart
applications and services. The feature is an opt-in, triggered by
xdg-desktop-autostart.target being activated.
Also included is the new binary xdg-autostart-condition. This binary is
used as an ExecCondition to test the OnlyShowIn and NotShowIn XDG
desktop file keys. These need to be evaluated against the
XDG_CURRENT_DESKTOP environment variable which may not be known at
generation time.
Co-authored-by: Henri Chain <henri.chain@enioka.com>
In our regular gettys the actual shell commands live the the session
scope anyway (as long as logind is used). Hence, let's avoid
KillMode=process, it serves no purpose and is simply unsafe since it
disables systemd's own process lifecycle management.
We want to watch USB sticks being plugged in, and that requires
AF_NETLINK to work correctly and get the host's events. But if we live
in a network namespace AF_NETLINK is disconnected too and we'll not get
the host udev events.
Fixes: #15287
Limit size of various tmpfs mounts to 10% of RAM, except volatile root and /var
to 25%. Another exception is made for /dev (also /devs for PrivateDevices) and
/sys/fs/cgroup since no (or very few) regular files are expected to be used.
In addition, since directories, symbolic links, device specials and xattrs are
not counted towards the size= limit, number of inodes is also limited
correspondingly: 4MB size translates to 1k of inodes (assuming 4k each), 10% of
RAM (using 16GB of RAM as baseline) translates to 400k and 25% to 1M inodes.
Because nr_inodes option can't use ratios like size option, there's an
unfortunate side effect that with small memory systems the limit may be on the
too large side. Also, on an extremely small device with only 256MB of RAM, 10%
of RAM for /run may not be enough for re-exec of PID1 because 16MB of free
space is required.
"Login Service" doesn''t explain much, esp. considering that logind is actually is
for logins. I think "User Login Management" is better, but not that great either.
Suggestions welcome.
We unregister binfmt_misc twice during shutdown with this change:
1. A previous commit added support for doing that in the final shutdown
phase, i.e. when we do the aggressive umount loop. This is the robust
thing to do, in case the earlier ("clean") shutdown phase didn't work
for some reason.
2. This commit adds support for doing that when systemd-binfmt.service
is stopped. This is a good idea so that people can order mounts
before the service if they want to register binaries from such
mounts, as in that case we'll undo the registration on shutdown
again, before unmounting those mounts.
And all that, just because of that weird "F" flag the kernel introduced
that can pin files...
Fixes: #14981
This doesn't really matter, since in non-/usr-merged systems plymouth
needs to be in /bin and on merged ones it doesn't matter, but it is
still prettier to insert the right path, and avoid /bin on merged
systems, since it's just a compat symlink.
Replaces: #15351
This dependency is now generated automatically given we use
StateDirectory=. Moreover the combination of Wants= and After= was too
strong anway, as whether remount-fs is pulled in or not should not be up
to systemd-pstore.service, and in fact is part of the initial
transaction anyway.
sysinit.target is the target our early boot services are generally
pulled in from, make systemd-pstore.service not an exception of that.
Effectively this doesn't mean much, either way our unit is part of the
initial transaction.
Add `ProtectClock=yes` to systemd units. Since it implies certain
`DeviceAllow=` rules, make sure that the units have `DeviceAllow=` rules so
they are still able to access other devices. Exclude timesyncd and timedated.
This reverts commit 7e1ed1f3b2.
systemd-repart is not a user service that should be something people
enable/disable, instead it should just work if there's configuration for
it. It's like systemd-tmpfiles, systemd-sysusers, systemd-load-modules,
systemd-binfmt, systemd-systemd-sysctl which are NOPs if they have no
configuration, and thus don't hurt, but cannot be disabled since they
are too deep part of the OS.
This doesn't mean people couldn't disable the service if they really
want to, there's after all "systemctl mask" and build-time disabling,
but those are OS developer facing instead of admin facing, that's how it
should be.
Note that systemd-repart is in particular an initrd service, and so far
enable/disable state of those is not managed anyway via "systemctl
enable/disable" but more what dracut decides to package up and what not.
/home is posibly a remote file system. it makes sense to order homed
after it, so that we can properly enumerate users in it, but we probably
shouldn't pull it in ourselves, and leave that to users to configure
otherwise.
Fixes: #15102
It's lightweight and generally useful, so it should be enabled by default. But
users might want to disable it for whatever reason, and things should be fine
without it, so let's make it installable so it can be disabled if wanted.
Fixes#15175.
This essentially adds another layer of configurability:
build disable, this, presence of configuration. The default is
set to enabled, because the service does nothing w/o config.
Possible alternative to #14819.
For me, setting RemainAfterExit=yes would be OK, but if people think that it
might cause issues, then this could be a reasonable alternative that still
let's us skip the invocation of the separate binary.
This reverts the second part of 8125e8d38e.
The first part was reverted in 750e550eba.
The problem starts when s-v-s.s is pulled in by something that is then pulled
in by sysinit.target. Every time a unit is started, systemd recursively checks
all dependencies, and since sysinit.target is pull in by almost anything, we'll
start s-v-s.s over and over. In particular, plymouth-start.service currently
has Wants=s-v-s.s and After=s-v-s.s.
This minus has been there since the unit was added in
d42d27ead9. I think the idea was not cause things
to fail if the user instance doesn't work. But ignoring the return value
doesn't seem to be the right way to approach the problem. In particular, if
the program fails to run, we'll get a bogus fail state, see
https://bugzilla.redhat.com/show_bug.cgi?id=1727895#c1:
with the minus:
$ systemctl start user@1002
Job for user@1002.service failed because the service did not take the steps required by its unit configuration.
See "systemctl status user@1002.service" and "journalctl -xe" for details.
without the minus:
$ systemctl start user@1002
Job for user@1002.service failed because the control process exited with error code.
See "systemctl status user@1002.service" and "journalctl -xe" for details.
This patch modifies the RequireMountsFor setting in systemd-nspawn@.service to wait for the machine instance directory to be mounted, not just /var/lib/machines.
Closes#14931
machined needs access to the host mount namespace to propagate bind
mounts created with the "machinectl bind" command. However, the
"ProtectKernelLogs" directive relies on mount namespaces to make the
kernel ring buffer inaccessible. This commit removes the
"ProtectKernelLogs=yes" directive from machined service file introduced
in 6168ae5.
Closes#14559.
Kernel 4.1 separated the tracing system from the debugfs,
actual documentation already points to a different path
that needs this new mount to exist.
the old sysfs path will still be an automount in the debugfs,
created by the kernel (for now).
Signed-off-by: Norbert Lange <nolange79@gmail.com>
See c80a9a33d0, target units can't fail.
I guess we need to figure out some replacement functionality, but at least
let's avoid the warning from systemd for now.
If we have exit on idle, then operations such as "journalctl
--namespace=foo --rotate" should work even if the journal daemon is
currently not running.
(Note that we don't do activation by varlink for the main instance of
journald, I am not sure the deadlocks it might introduce are worth it)
This makes things a bit simpler and the build a bit faster, because we don't
have to rewrite files to do the trivial substitution. @rootbindir@ is always in
our internal $PATH that we use for non-absolute paths, so there should be no
functional change.
Let's use uppercase wording in the description string, like we usually
do.
Let's allow using this service in early boot.
If it's pulled into the initial transaction it's better to finish
loading this before sysinit.target.
Don't bother with this in containers that lack CAP_SYS_MODULE
Devices referred to by `DeviceAllow=` sandboxing are resolved into their
corresponding major numbers when the unit is loaded by looking at
`/proc/devices`. If a reference is made to a device which is not yet
available, the `DeviceAllow` is ignored and the unit's processes cannot
access that device.
In both logind and nspawn, we have `DeviceAllow=` lines, and `modprobe`
in `ExecStartPre=` to load some kernel modules. Those kernel modules
cause device nodes to become available when they are loaded: the device
nodes may not exist when the unit itself is loaded. This means that the
unit's processes will not be able to access the device since the
`DeviceAllow=` will have been resolved earlier and denied it.
One way to fix this would be to re-evaluate the available devices and
re-apply the policy to the cgroup, but this cannot work atomically on
cgroupsv1. So we fall back to a second approach: instead of running
`modprobe` via `ExecStartPre`, we move this out to a separate unit and
order it before the units which want the module.
Closes#14322.
Fixes: #13943.
This reverts commit 07125d24ee.
In contrast to what is claimed in #13396 dbus-broker apparently does
care for the service file to be around, and otherwise will claim
"Service Not Activatable" in the time between systemd starting up the
broker and connecting to it, which the stub service file is supposed to
make go away.
Reverting this makes the integration test suite pass again on host with
dbus-broker (i.e. current Fedora desktop).
Tested with dbus-broker-21-6.fc31.x86_64.
This reverts commit 362c378291.
This commit introduced an ordering loop: remote-cryptsetup.target was both
before and after remote-fs-pre.target. It also globally ordered all cryptsetup
volumes before all mounts. Such global ordering is problematic if people have
stacked storage. Let's look for a different solution.
See https://github.com/systemd/systemd/pull/14378#discussion_r359460109.
Otherwise, systemd-udev-trigger|settle.service that ran in the initrd may
ramain active, and never re-run again from the system root.
This is observed by forexample examining ESP with udevadm info, which in the
initrd has all the ID_* variables, and none of them in fully booted system.
This option is an indication for PID1 that the entry in crypttab is handled by
initrd only and therefore it shouldn't interfer during the usual start-up and
shutdown process.
It should be primarily used with the encrypted device containing the root FS as
we want to keep it (and thus its encrypted device) until the very end of the
shutdown process, i.e. when initrd takes over.
This option is the counterpart of "x-initrd.mount" used in fstab.
Note that the slice containing the cryptsetup services also needs to drop the
usual shutdown dependencies as it's required by the cryptsetup services.
Fixes: #14224
Apparently some firmwares don't allow us to write this token, and refuse
it with EINVAL. We should normally consider that a fatal error, but not
really in the case of "bootctl random-seed" when called from the
systemd-boot-system-token.service since it's called as "best effort"
service after boot on various systems, and hence we shouldn't fail
loudly.
Similar, when we cannot find the ESP don't fail either, since there are
systems (arch install ISOs) that carry a boot loader capable of the
random seed logic but don't mount it after boot.
Fixes: #13603
We set ProtectKernelLogs=yes on all long running services except for
udevd, since it accesses /dev/kmsg, and journald, since it calls syslog
and accesses /dev/kmsg.
As discussed on systemd-devel [1], in Fedora we get lots of abrt reports
about the watchdog firing [2], but 100% of them seem to be caused by resource
starvation in the machine, and never actual deadlocks in the services being
monitored. Killing the services not only does not improve anything, but it
makes the resource starvation worse, because the service needs cycles to restart,
and coredump processing is also fairly expensive. This adds a configuration option
to allow the value to be changed. If the setting is not set, there is no change.
My plan is to set it to some ridiculusly high value, maybe 1h, to catch cases
where a service is actually hanging.
[1] https://lists.freedesktop.org/archives/systemd-devel/2019-October/043618.html
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1300212
The code supports SIGTERM and SIGINT to termiante the process. It would
be possible to reporpose one of those signals for the restart operation,
but I think it's better to use a completely different signal to avoid
misunderstandings.
See https://bugzilla.redhat.com/show_bug.cgi?id=1731772:
when autofs4 is disabled in the kernel,
proc-sys-fs-binfmt_misc.automount is not started, so the binfmt_misc module is
never loaded. If we added a dependency on proc-sys-fs-binfmt_misc.mount
to systemd-binfmt.service, things would work even if autofs4 was disabled, but
we would unconditionally pull in the module and mount, which we don't want to do.
(Right now we ony load the module if some binfmt is configured.)
But let's make it easier to handle this case by doing two changes:
1. order systemd-binfmt.service after the .mount unit (so that the .service
can count on the mount if both units are pulled in, even if .automount
is skipped)
2. add [Install] section to the service unit. This way the user can do
'systemctl enable proc-sys-fs-binfmt_misc.mount' to get the appropriate behaviour.
This fixes the following problem:
> At the very end of the boot, just after the first user logs in
> (usually using sddm / X) I get the following messages in my logs:
> Nov 18 07:02:33 samd dbus-daemon[2879]: [session uid=1000 pid=2877] Activated service 'org.freedesktop.systemd1' failed: Process org.freedesktop.systemd1 exited with status 1
> Nov 18 07:02:33 samd dbus-daemon[2879]: [session uid=1000 pid=2877] Activated service 'org.freedesktop.systemd1' failed: Process org.freedesktop.systemd1 exited with status 1
These messages are caused by the "stub" service files that systemd
installs. It installed them because early versions of systemd activation
required them to exist.
Since dbus 1.11.0, a dbus-daemon that is run with --systemd-activation
automatically assumes that o.fd.systemd1 is an activatable
service. As a result, with a new enough dbus version,
/usr/share/dbus-1/services/org.freedesktop.systemd1.service and
/usr/share/dbus-1/system-services/org.freedesktop.systemd1.service should
become unnecessary, and they can be removed.
dbus 1.11.0 was released 2015-12-02.
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=914015
If logging disappears issues are hard to debug, hence let's give
journald a slight edge over other services when the OOM killer hits.
Here are the special adjustments we now make:
systemd-coredump@.service.in OOMScoreAdjust=500
systemd-journald.service.in OOMScoreAdjust=-250
systemd-udevd.service.in OOMScoreAdjust=-1000
(i.e. the coredump processing is made more likely to be killed on OOM,
and udevd and journald are less likely to be killed)
Follow-up for 26ded55709.
The commit says,
> Note that with this change sysinit.target (and thus early boot) is NOT
systematically delayed until the entropy pool is initialized,
But the dependency was not dropped.
This was found by David Seifert (@SoapGentoo).
This makes two major changes to the way systemd-random-seed operates:
1. We now optionally credit entropy if this is configured (via an env
var). Previously we never would do that, with this change we still don't
by default, but it's possible to enable this if people acknowledge that
they shouldn't replicate an image with a contained random seed to
multiple systems. Note that in this patch crediting entropy is a boolean
thing (unlike in previous attempts such as #1062), where only a relative
amount of bits was credited. The simpler scheme implemented here should
be OK though as the random seeds saved to disk are now written only with
data from the kernel's entropy pool retrieved after the pool is fully
initialized. Specifically:
2. This makes systemd-random-seed.service a synchronization point for
kernel entropy pool initialization. It was already used like this, for
example by systemd-cryptsetup-generator's /dev/urandom passphrase
handling, with this change it explicitly operates like that (at least
systems which provide getrandom(), where we can support this). This
means services that rely on an initialized random pool should now place
After=systemd-random-seed.service and everything should be fine. Note
that with this change sysinit.target (and thus early boot) is NOT
systematically delayed until the entropy pool is initialized, i.e.
regular services need to add explicit ordering deps on this service if
they require an initialized random pool.
Fixes: #4271
Replaces: #10621#4513
This reverts commit 971a7a1526.
These unit names are typically different on distributions, let's not
hardcode those. Stuff like this should probably live in the distro
RPM/.deb, but not upstream, where we should be distro agnostic and
agnostic to other higher level packages like this.
Users might end up with more than one of those service enabled, through
admin mistake, or broken installation scriptlets, or whatever. On my machine,
I had both chronyd and timesyncd happilly running at the same time. If
more than one is enabled, it's better to have just one running. Adding
Conflicts will make the issue more visible in logs too.
This patch introduces the systemd pstore service which will archive the
contents of the Linux persistent storage filesystem, pstore, to other storage,
thus preserving the existing information contained in the pstore, and clearing
pstore storage for future error events.
Linux provides a persistent storage file system, pstore[1], that can store
error records when the kernel dies (or reboots or powers-off). These records in
turn can be referenced to debug kernel problems (currently the kernel stuffs
the tail of the dmesg, which also contains a stack backtrace, into pstore).
The pstore file system supports a variety of backends that map onto persistent
storage, such as the ACPI ERST[2, Section 18.5 Error Serialization] and UEFI
variables[3 Appendix N Common Platform Error Record]. The pstore backends
typically offer a relatively small amount of persistent storage, e.g. 64KiB,
which can quickly fill up and thus prevent subsequent kernel crashes from
recording errors. Thus there is a need to monitor and extract the pstore
contents so that future kernel problems can also record information in the
pstore.
The pstore service is independent of the kdump service. In cloud environments
specifically, host and guest filesystems are on remote filesystems (eg. iSCSI
or NFS), thus kdump relies [implicitly and/or explicitly] upon proper operation
of networking software *and* hardware *and* infrastructure. Thus it may not be
possible to capture a kernel coredump to a file since writes over the network
may not be possible.
The pstore backend, on the other hand, is completely local and provides a path
to store error records which will survive a reboot and aid in post-mortem
debugging.
Usage Notes:
This tool moves files from /sys/fs/pstore into /var/lib/systemd/pstore.
To enable kernel recording of error records into pstore, one must either pass
crash_kexec_post_notifiers[4] to the kernel command line or enable via 'echo Y
> /sys/module/kernel/parameters/crash_kexec_post_notifiers'. This option
invokes the recording of errors into pstore *before* an attempt to kexec/kdump
on a kernel crash.
Optionally, to record reboots and shutdowns in the pstore, one can either pass
the printk.always_kmsg_dump[4] to the kernel command line or enable via 'echo Y >
/sys/module/printk/parameters/always_kmsg_dump'. This option enables code on the
shutdown path to record information via pstore.
This pstore service is a oneshot service. When run, the service invokes
systemd-pstore which is a tool that performs the following:
- reads the pstore.conf configuration file
- collects the lists of files in the pstore (eg. /sys/fs/pstore)
- for certain file types (eg. dmesg) a handler is invoked
- for all other files, the file is moved from pstore
- In the case of dmesg handler, final processing occurs as such:
- files processed in reverse lexigraphical order to faciliate
reconstruction of original dmesg
- the filename is examined to determine which dmesg it is a part
- the file is appended to the reconstructed dmesg
For example, the following pstore contents:
root@vm356:~# ls -al /sys/fs/pstore
total 0
drwxr-x--- 2 root root 0 May 9 09:50 .
drwxr-xr-x 7 root root 0 May 9 09:50 ..
-r--r--r-- 1 root root 1610 May 9 09:49 dmesg-efi-155741337601001
-r--r--r-- 1 root root 1778 May 9 09:49 dmesg-efi-155741337602001
-r--r--r-- 1 root root 1726 May 9 09:49 dmesg-efi-155741337603001
-r--r--r-- 1 root root 1746 May 9 09:49 dmesg-efi-155741337604001
-r--r--r-- 1 root root 1686 May 9 09:49 dmesg-efi-155741337605001
-r--r--r-- 1 root root 1690 May 9 09:49 dmesg-efi-155741337606001
-r--r--r-- 1 root root 1775 May 9 09:49 dmesg-efi-155741337607001
-r--r--r-- 1 root root 1811 May 9 09:49 dmesg-efi-155741337608001
-r--r--r-- 1 root root 1817 May 9 09:49 dmesg-efi-155741337609001
-r--r--r-- 1 root root 1795 May 9 09:49 dmesg-efi-155741337710001
-r--r--r-- 1 root root 1770 May 9 09:49 dmesg-efi-155741337711001
-r--r--r-- 1 root root 1796 May 9 09:49 dmesg-efi-155741337712001
-r--r--r-- 1 root root 1787 May 9 09:49 dmesg-efi-155741337713001
-r--r--r-- 1 root root 1808 May 9 09:49 dmesg-efi-155741337714001
-r--r--r-- 1 root root 1754 May 9 09:49 dmesg-efi-155741337715001
results in the following:
root@vm356:~# ls -al /var/lib/systemd/pstore/155741337/
total 92
drwxr-xr-x 2 root root 4096 May 9 09:50 .
drwxr-xr-x 4 root root 40 May 9 09:50 ..
-rw-r--r-- 1 root root 1610 May 9 09:50 dmesg-efi-155741337601001
-rw-r--r-- 1 root root 1778 May 9 09:50 dmesg-efi-155741337602001
-rw-r--r-- 1 root root 1726 May 9 09:50 dmesg-efi-155741337603001
-rw-r--r-- 1 root root 1746 May 9 09:50 dmesg-efi-155741337604001
-rw-r--r-- 1 root root 1686 May 9 09:50 dmesg-efi-155741337605001
-rw-r--r-- 1 root root 1690 May 9 09:50 dmesg-efi-155741337606001
-rw-r--r-- 1 root root 1775 May 9 09:50 dmesg-efi-155741337607001
-rw-r--r-- 1 root root 1811 May 9 09:50 dmesg-efi-155741337608001
-rw-r--r-- 1 root root 1817 May 9 09:50 dmesg-efi-155741337609001
-rw-r--r-- 1 root root 1795 May 9 09:50 dmesg-efi-155741337710001
-rw-r--r-- 1 root root 1770 May 9 09:50 dmesg-efi-155741337711001
-rw-r--r-- 1 root root 1796 May 9 09:50 dmesg-efi-155741337712001
-rw-r--r-- 1 root root 1787 May 9 09:50 dmesg-efi-155741337713001
-rw-r--r-- 1 root root 1808 May 9 09:50 dmesg-efi-155741337714001
-rw-r--r-- 1 root root 1754 May 9 09:50 dmesg-efi-155741337715001
-rw-r--r-- 1 root root 26754 May 9 09:50 dmesg.txt
where dmesg.txt is reconstructed from the group of related
dmesg-efi-155741337* files.
Configuration file:
The pstore.conf configuration file has four settings, described below.
- Storage : one of "none", "external", or "journal". With "none", this
tool leaves the contents of pstore untouched. With "external", the
contents of the pstore are moved into the /var/lib/systemd/pstore,
as well as logged into the journal. With "journal", the contents of
the pstore are recorded only in the systemd journal. The default is
"external".
- Unlink : is a boolean. When "true", the default, then files in the
pstore are removed once processed. When "false", processing of the
pstore occurs normally, but the pstore files remain.
References:
[1] "Persistent storage for a kernel's dying breath",
March 23, 2011.
https://lwn.net/Articles/434821/
[2] "Advanced Configuration and Power Interface Specification",
version 6.2, May 2017.
https://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf
[3] "Unified Extensible Firmware Interface Specification",
version 2.8, March 2019.
https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_final.pdf
[4] "The kernel’s command-line parameters",
https://static.lwn.net/kerneldoc/admin-guide/kernel-parameters.html
We use that on all other services, and hence should here too. Otherwise
the service will be killed with SIGSYS when doing something not
whitelisted, which is a bit crass.
While the need for access to character devices can be tricky to determine for
the general case, it's obvious that most of our services have no need to access
block devices. For logind and timedated this can be tightened further.
