We have a common parser, but for the user it might be
completely unobvious that the same general rules apply
to all those files. Let's add a page about the basic syntax
so that the more specific pages don't have to repeat those
details.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
So far we didn't document control, transient, dbus config, or generator paths.
But those paths are visible to users, and they need to understand why systemd
loads units from those paths, and how the precedence hierarchy looks.
The whole thing is a bit messy, since the list of paths is quite long.
I made the tables a bit shorter by combining rows for the alternatives
where $XDG_* is set and the fallback.
In various places, tags are split like <element
param="blah">
this. This is necessary to keep everyting in one logical XML line so that
docbook renders the table properly.
Replaces #8050.
Follow-up for e79eabdb1b. There was an
apparent contradiction:
man/systemd.unit says for Requires=:
Besides, with or without specifying After=, this unit will be deactivated
if one of the other units get deactivated.
Also, some unit types may deactivate on their own (for example, a service
process may decide to exit cleanly, or a device may be unplugged by the
user), which is not propagated to units having a Requires= dependency.
Fixes#7870.
This adds a simple condition/assert/match to the service manager, to
udev's .link handling and to networkd, for matching the kernel version
string.
In this version we only do fnmatch() based globbing, but we might want
to extend that to version comparisons later on, if we like, by slightly
extending the syntax with ">=", "<=", ">", "<" and "==" expressions.
Up until now, the behaviour in systemd has (mostly) been to silently
ignore failures to action unit directives that refer to an unavailble
controller. The addition of AssertControlGroupController and its
conditional counterpart allow explicit specification of the desired
behaviour when such a situation occurs.
As for how this can happen, it is possible that a particular controller
is not available in the cgroup hierarchy. One possible reason for this
is that, in the running kernel, the controller simply doesn't exist --
for example, the CPU controller in cgroup v2 has only recently been
merged and was out of tree until then. Another possibility is that the
controller exists, but has been forcibly disabled by `cgroup_disable=`
on the kernel command line.
In future this will also support whatever comes out of issue #7624,
`DefaultXAccounting=never`, or similar.
It would be nicer to use <footnote> to place the notes directly in the table,
but docbook renders this improperly.
v2:
- also add "RequiredBy=" to the notes section
- remove duplicated paragraph
v3:
- clarify the description
- drop References/ReferenceBy which are only shown in systemd-analyze dump
The code intentionally ignored unknown specifiers, treating them as text. This
needs to change because otherwise we can never add a new specifier in a backwards
compatible way. So just treat an unknown (potential) specifier as an error.
In principle this is a break of backwards compatibility, but the previous
behaviour was pretty much useless, since the expanded value could change every
time we add new specifiers, which we do all the time.
As a compromise for backwards compatibility, only fail on alphanumerical
characters. This should cover the most cases where an unescaped percent
character is used, like size=5% and such, which behave the same as before with
this patch. OTOH, this means that we will not be able to use non-alphanumerical
specifiers without breaking backwards compatibility again. I think that's an
acceptable compromise.
v2:
- add NEWS entry
v3:
- only fail on alphanumerical
SuccessAction= is similar to FailureAction= but declares what to do on
success of a unit, rather than on failure. This is useful for running
commands in qemu/nspawn images, that shall power down on completion. We
frequently see "ExecStopPost=/usr/bin/systemctl poweroff" or so in unit
files like this. Offer a simple, more declarative alternative for this.
While we are at it, hook up failure action with unit_dump() and
transient units too.
Right now, the option only takes one of two possible values "inactive"
or "inactive-or-failed", the former being the default, and exposing same
behaviour as the status quo ante. If set to "inactive-or-failed" units
may be collected by the GC logic when in the "failed" state too.
This logic should be a nicer alternative to using the "-" modifier for
ExecStart= and friends, as the exit data is collected and logged about
and only removed when the GC comes along. This should be useful in
particular for per-connection socket-activated services, as well as
"systemd-run" command lines that shall leave no artifacts in the
system.
I was thinking about whether to expose this as a boolean, but opted for
an enum instead, as I have the suspicion other tweaks like this might be
a added later on, in which case we extend this setting instead of having
to add yet another one.
Also, let's add some documentation for the GC logic.
This augments %t which already resolves to the runtime directory root, and
should be useful for units that want to pass any of these paths in
command line arguments.
Example:
ExecStart=/usr/bin/mydaemon --datadir=%S/mydaemon
Why not expose a specifier resolving directly to the configured
state/runtime/cache/log dir? Three reasons:
1. Specifiers should be independent of configuration of the unit itself,
and StateDirectory= and friends are unit configuration. See
03fc9c723c and related work.
2. We permit multiple StateDirectory= values per unit, and it hence
wouldn't be clear which one is passed.
3. We already have %t for the runtime directory root, and we should
continue with the same scheme.
We settled on "filename" and "file system", so change a couple of places for
consistency. The exception is when there's an adjective before "file" that
binds more strongly then "name": "password file name", "output file name", etc.
Those cases are left intact.
The values for StartLimitAction are defined in `man systemd.unit`.
Don't send people to `man systemd.service` just to find they need to look
back in `man systemd.unit` again :).
This adds two options that are useful for user units. In particular, it
is useful to check ConditionUser=!0 to not start for the root user.
Closes: #5187
Zbigniew Jędrzejewski-Szmek