For CI in mkosi, I want to configure systemd to log at debug level
to the journal, but not to the console. While we already have max
level settings for journald's forwarding settings, not every log line
goes to the journal, specifically during early boot and when units
are connected directly to the console (think systemd-firstboot), so
let's extend the log level options we already have to allow specifying
a comma separated list of values and lets allow prefixing values with
the log target they apply to to make this possible.
This geneally makes sense as setting up a PAM session pretty much
defines what a login session is.
In context of #30547 this has the benefit that we can take benefit of
the SetLoginEnvironment= effect without having to set it explicitly,
thus retaining some compat of the uid0 client towards older systemd
service managers.
This is the common case in --user instances, hence handle this
gracefully.
This should be safe since user instances won't get access to
/dev/console-related ttys anyway, but only their own ptys.
Those functions take a pointer to a timestamp and return a timestamp pointer,
so the reader would be justified to think that those are just getters. Rename
them to avoid confusion.
This combines exec_context_determine_tty_size() and
terminal_set_size_fd() since we always use one after the other.
Also make exec_context_determine_tty_size() return void, since it cannot
fail.
We use it for more than just pipe() arrays. For example also for
socketpair(). Hence let's give it a generic name.
Also add EBADF_TRIPLET to mirror this for things like
stdin/stdout/stderr arrays, which we use a bunch of times.
We usually check return value of syscalls or glibc functions by it is
negative or not, something like that `if (stat(path, &st) < 0)`.
Let's also use the same style for lseek() and friends even the type of
their return value is off_t.
Note, fseeko() returns int, instead of off_t.
Currently, when we deserialize an fd we do a lot of manual work. Add a
common helper that makes this more robust and uniform.
Note that this sometimes changes behaviour slightly, but in ways that
shouldn't really matter: if we fail to deserialize an fd correctly we'll
unset (i.e. set to -EBADF) the fd in the deserialized data structure.
Previously, we'd leave the old value in place.
This should not change effective result (as in either case we'll be in a
bad state afterwards, just once we mix old/invalidated state with new
state, while now we'll reset the state explicitly to invalidated state
on failure). In particular as deserialization starts from an empty
structure generally, hence the old value should be unset anyway.
Another slight change is that if we fail to deserialize some object half
way, and we already have taken out one fd from the serialized fdset
we'll now just close it instead of returning it to/leaving it in the
fdset. Given that such "orphaned" fds are blanket closed after
deserialization finishes this also shouldn't change behaviour IRL.
Also, the idle_pipe was previously incorrectly serialized: we'd
serialize invalidated fds, which would fail, but because parsing errors
on this were ignored on the deserializatin noone noticed. This is fixed.
No functional changes, only moving code that is only needed in
exec_invoke, and adding new dependencies for seccomp/selinux/apparmor/pam
in meson for the sd-executor binary.
Currently we spawn services by forking a child process, doing a bunch
of work, and then exec'ing the service executable.
There are some advantages to this approach:
- quick: we immediately have access to all the enourmous amount of
state simply by virtue of sharing the memory with the parent
- easy to refactor and add features
- part of the same binary, will never be out of sync
There are however significant drawbacks:
- doing work after fork and before exec is against glibc's supported
case for several APIs we call
- copy-on-write trap: anytime any memory is touched in either parent
or child, a copy of that page will be triggered
- memory footprint of the child process will be memory footprint of
PID1, but using the cgroup memory limits of the unit
The last issue is especially problematic on resource constrained
systems where hard memory caps are enforced and swap is not allowed.
As soon as PID1 is under load, with no page out due to no swap, and a
service with a low MemoryMax= tries to start, hilarity ensues.
Add a new systemd-executor binary, that is able to receive all the
required state via memfd, deserialize it, prepare the appropriate
data structures and call exec_child.
Use posix_spawn which uses CLONE_VM + CLONE_VFORK, to ensure there is
no copy-on-write (same address space will be used, and parent process
will be frozen, until exec).
The sd-executor binary is pinned by FD on startup, so that we can
guarantee there will be no incompatibilities during upgrades.
Before this commit, $USER, $HOME, $LOGNAME and $SHELL are only
set when User= is set for the unit. For system service, this
results in different behaviors depending on whether User=root is set.
$USER always makes sense on its own, so let's set it unconditionally.
Ideally $HOME should be set too, but it causes trouble when e.g. getty
passes '-p' to login(1), which then doesn't override $HOME. $LOGNAME and
$SHELL are more like "login environments", and are generally not
suitable for system services. Therefore, a new option SetLoginEnvironment=
is also added to control the latter three variables.
Fixes#23438
Replaces #8227
Mike Yuan
Yu Watanabe
Daan De Meyer
Lennart Poettering
Luca Boccassi
Zbigniew Jędrzejewski-Szmek
Frantisek Sumsal