Follow-up for fa693fdc7e.
The documentation says the option takes a boolean or one of the "self"
and "identity". But the parser uses private_users_from_string() which
also accepts "off". Let's drop the implicit support of "off".
This adds the ExtraFileDescriptor property to StartTransient dbus API
with format "a(hs)" - array of (file descriptor, name) pairs. The FD
will be passed to the unit via sd_notify like Socket and OpenFile.
systemctl show also shows ExtraFileDescriptorName for these transient
units. We only show the name passed to dbus as the FD numbers will
change once passed over the unix socket and are duplicated, so its
confusing to display the numbers.
We do not add this functionality for systemd-run or general systemd
service units as it is not useful for general systemd services.
Arguably, it could be useful for systemd-run in bash scripts but we
prefer to be cautious and not expose the API yet.
Fixes: #34396
When dealing with copying COW images, we have to make a tradeoff:
- Either we don't touch the NOCOW bit on the copied file COW and get
an instant copy because we're able to reflink, but we might get
reduced performance if the source file was COW as COW files and lots
of random writes don't play well together.
- Or we force NOCOW for the copied file, which means we have to do a
full copy as reflinking from COW files to NOCOW files or vice versa
is not supported.
In exec-invoke.c, we've opted for the first option. In nspawn.c and
discover-image.c, we've opted for the second option.
In nspawn, this applies to the --ephemeral option to make ephemeral
copies. In discover-image.c, this applies to cloning images into
/var/lib/machines. Both these features might be used to run many
machines of the same original image. We really don't want to force
a full copy onto users in these scenarios when they're expecting
reflink behavior, leading to them running out of disk space. Instead,
degraded performance in their machines is a much less severe issue,
which they will discover on their own if it affects them, at which
point they can make their original image NOCOW at which point they'll
get both the reflinks and better performance.
Given the above reasoning, let's switch nspawn.c and discover-image.c
to use COPY_NOCOW_AFTER as well instead of enabling NOCOW upfront and
forcing a copy if the original source image is COW.
One of the major pait points of managing fleets of headless nodes is
that when something fails at startup, unless debug level was already
enabled (which usually isn't, as it's a firehose), one needs to manually
enable it and pray the issue can be reproduced, which often is really
hard and time consuming, just to get extra info. Usually the extra log
messages are enough to triage an issue.
This new option makes it so that when a service fails and is restarted
due to Restart=, log level for that unit is set to debug, so that all
setup code in pid1 and sd-executor logs at debug level, and also a new
DEBUG_INVOCATION=1 env var is passed to the service itself, so that it
knows it should start with a higher log level. Once the unit succeeds
or reaches the rate limit the original level is restored.
The nice value is part of struct sched_attr, and consequently invoking
sched_setattr() after setpriority() would clobber the nice value with
the default (as we are not setting it in struct sched_attr).
It would be best to combine both calls, but for now simply invoke
setpriority() after sched_setattr() to make sure Nice= remains effective
when used together with CPUSchedulingPolicy=.
With ambient capabilities being dropped at the start of process managers
(both system and user) as well as systemd-executor it isn't necessary
to drop them here. Moreover, at this point also the inheritable set can
be preserved. This makes it possible to assign a user session manager
inheritable capabilities which combined with file capabilites (ei sets)
of service executables enable running user services with capabilities
but only when started by the manager.
This reverts commit 943800f4e7.
Since the copy helpers now copy file attributes as well, let's not
explicitly disable copy-on-write anymore when we copy an image. If
the source already has copy-on-write disabled, the copy will have it
disabled as well. Otherwise, the copy will also have copy-on-write
enabled.
This makes sure that reflinks always work as reflink is only supported
if both source and target are copy-on-write or both source and target
are not copy-on-write.
It doesn't really make sense to have that in dev-setup.c, which is
mostly about setting up /dev/, creating device nodes and stuff.
let's move it to the other stuff that deals with /dev/console's
peculiarities.
It's a bit confusing, but we actually initialize the terminal twice for
each service, potentially. One earlier time, where we might end up
firing vhangup() and vt_disallocate(), which is a pretty brutal way to
reset things, by disconnecting and possibly invalidating the tty
completely. When we do this we do not keep any fd open afterwards, since
it quite likely points to a dead connection of a tty.
The 2nd time we initialize things when we actually want to use it.
The first initialization is hence "destructive" (killing any left-overs
from previous uses) the 2nd one "constructive" (preparing things for our
new use), if you so will.
Let's document this distinction in comments, and let's also move both
initializations to exec_invoke(), so that they are easier to see in their
symmetric behaviour. Moreover, let's run the tty initialization after we
opened both input and output, since we need both for doing the fancy
dimension auto init stuff now.
Oh, and of course, one thing to mention: we nowadays initialize
terminals both with ioctl() and with ansi sequences. But the latter
means we need an fd that is open for *write* (since we are *writing*
those ansi sequences to the tty). Hence, resetting via the input fd is
conceptually wrong, it worked only so far if we had O_RDWR open mode
selected)
And while we are at it, merge exec_context_determine_tty_size() +
exec_context_apply_tty_size().
Let's simplify things, and merge the two funcs, since the latter just
does one more call.
At the same time, let's make sure we actually allow passing separate
input/output fds.
The kernel's sched_setattr interface allows for more control over a processes
scheduling attributes as the previously used sched_setscheduler interface.
Using sched_setattr is also the prerequisite for support of utilization
clamping (UCLAMP [1], see #26705) and allows to set sched_runtime. The latter,
sched_runtime, will probably become a relevant scheduling parameter of the
EEVDF scheduler [2, 3], and therefore will not only apply to processes
scheduled via SCHED_DEADLINE, but also for processes scheduled via
SCHED_OTHER/SCHED_BATCH (i.e., most processes).
1: https://docs.kernel.org/next/scheduler/sched-util-clamp.html
2: https://lwn.net/Articles/969062/
3: https://lwn.net/ml/linux-kernel/20240405110010.934104715@infradead.org/
Before 12001b1bf0, write() is required for
if Type=exec. However, with the previous commit, now write() is also used
for sending handoff timestamp. Let's allow write() if necessary.
Fixes a regression caused by 12001b1bf0.
Fixes#33299.
Before 12001b1bf0, the timestamp is sent
with write(), but the commit made the timestamp sent by send(), and
causes regressin #33299.
Note the invocation will still fail if write() is filtered by seccomp.
But, that is an old issue since Type=exec is introduced
(5686391b00).
Partially fixes a regression caused by 12001b1bf0.
Partially fixes#33299.
DynamicUser= enables PrivateTmp= implicitly to avoid files owned by reusable uids
leaking into the host. Change it to instead create a fully private tmpfs instance
instead, which also ensures the same result, since it has less impactful semantics
with respect to PrivateTmp=yes, which links the mount namespace to the host's /tmp
instead. If a user specifies PrivateTmp manually, let the existing behaviour
unchanged to ensure backward compatibility is not broken.
- drop unnecessary SYNTHETIC_ERRNO() when the logger does not propagate
error code,
- drop unnecessary '%m' in error message when the error code is
specified with SYNTHETIC_ERRNO(),
- add missing full stop at the end of log message,
- use RET_GATHER(),
- add missing ", ignoring.",
- upeercase the first letter, etc., etc...
This changes the executor to systematically send handoff timestamps to
the service manager if a socket for that is supplied. This drops the
code that did this via Type=exec messages, and reverts that part to the
old behaviour before 93cb78aee2.
Benefits of this approach:
1. We can collect the handoff for any command we fork off, regardless
if it's ExecStart= something else, regardless whether it's Type=exec,
Type=simple or some any other service type, regardless of the unit
type.
2. We collect both CLOCK_REALTIME and CLOCK_MONOTONIC, as we do for the
other process timestamps.
3. It's entirely backwards compatible, as this doesn't change the
protocol between service manager and executor, but just extends it.
Enable the exec_fd logic for Type=notify* services too, and change it
to send a timestamp instead of a '1' byte. Record the timestamp in a
new ExecMainHandoverTimestamp property so that users can track accurately
when control is handed over from systemd to the service payload, so
that latency and startup performance can be trivially and accurately
tracked and attributed.
Use FOREACH_ELEMENT where possible. Generated with this command,
and checked manually:
git grep -l 'FOREACH_ARRAY.*ELEMENTSOF' | \
xargs sed -ri 's/FOREACH_ARRAY\((.*), (.*), (ELEMENTSOF.*)\)/FOREACH_ELEMENT(\1, \2)/'
Prompted by #32259
We already have this check in exec_invoke(), i.e. child.
But if CLONE_INTO_CGROUP is used, the failure would
occur on parent's side, so do the check there too.
Yu Watanabe
Ryan Wilson
Mike Yuan
Daan De Meyer
Lennart Poettering
Luca Boccassi
Ivan Shapovalov
Łukasz Stelmach
Florian Schmaus
David Tardon
Dmitry V. Levin
Matteo Croce