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install: allow adding plain templates to .wants/ or .requires/

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Fixes #19437.

As reported in the bug:

> # drkonqi-coredump-processor@.service
>  ...
> [Install]
> WantedBy=systemd-coredump@.service
>
> The plan here is to have a systemd-coredump@ instance start the same %i for
> drkonqi-coredump-processor@. Works perfectly when creating the symlink manually
> ln -sv /usr/lib/systemd/system/drkonqi-coredump-processor@.service
> /etc/systemd/system/systemd-coredump@.service.wants/.

When DefaultInstance is set, we replace template references with
template@default-inst. But in this case we want to create a symlink for the
template name, so that systemd will fill in the instance from the
wanting/requiring unit. This is only possible for those units that actually
have an instance set, so we create the symlink only from .requires/ or .wants
of an instantiated unit (then this specific instance will be used), or a
template (than some instance will be inherited later).

Specifically:
...
[Install]
WantedBy=other@.service, fixed.service
DefaultInstance=inst

→ enable foo@.service creates other@.service.wants/foo@inst.service, and
other@a.service will want foo@inst.service, and other@b.service will want foo@inst.service,
and fixed.service will want foo@inst.service.

Without DefaultInstance,
→ enable foo@.service creates other@.service.wants/foo@.service, and
other@a.service would want foo@a.service, and other@b.service would want foo@b.service,
but enablement fails because no dependency can be created for fixed.service:

  Failed to enable unit, unit fixed.service is a non-template unit.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2021-06-04 15:26:37 +02:00 committed by Yu Watanabe
parent 6260e85fc8
commit b0ec372a96
1 changed files with 30 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
src/shared/install.c
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@ -376,6 +376,11 @@ void unit_file_dump_changes(int r, const char *verb, const UnitFileChange *chang
verb, changes[i].path);
logged = true;
break;
case -EIDRM:
log_error_errno(changes[i].type_or_errno, "Failed to %s unit, unit %s is a non-template unit.",
verb, changes[i].path);
logged = true;
break;
case -EUCLEAN:
log_error_errno(changes[i].type_or_errno,
"Failed to %s unit, \"%s\" is not a valid unit name.",
@ -1847,6 +1852,7 @@ static int install_info_symlink_wants(
size_t *n_changes) {
_cleanup_free_ char *buf = NULL;
UnitNameFlags valid_dst_type = UNIT_NAME_ANY;
const char *n;
char **s;
int r = 0, q;
@ -1858,15 +1864,17 @@ static int install_info_symlink_wants(
if (strv_isempty(list))
return 0;
if (unit_name_is_valid(i->name, UNIT_NAME_TEMPLATE)) {
if (unit_name_is_valid(i->name, UNIT_NAME_PLAIN | UNIT_NAME_INSTANCE))
/* Not a template unit. Use the name directly. */
n = i->name;
else if (i->default_instance) {
UnitFileInstallInfo instance = {
.type = _UNIT_FILE_TYPE_INVALID,
};
_cleanup_free_ char *path = NULL;
/* If this is a template, and we have no instance, don't do anything */
if (!i->default_instance)
return 1;
/* If this is a template, and we have a default instance, use it. */
r = unit_name_replace_instance(i->name, i->default_instance, &buf);
if (r < 0)
@ -1885,8 +1893,14 @@ static int install_info_symlink_wants(
}
n = buf;
} else
} else {
/* We have a template, but no instance yet. When used with an instantiated unit, we will get
* the instance from that unit. Cannot be used with non-instance units. */
valid_dst_type = UNIT_NAME_INSTANCE | UNIT_NAME_TEMPLATE;
n = i->name;
}
STRV_FOREACH(s, list) {
_cleanup_free_ char *path = NULL, *dst = NULL;
@ -1895,9 +1909,17 @@ static int install_info_symlink_wants(
if (q < 0)
return q;
if (!unit_name_is_valid(dst, UNIT_NAME_ANY)) {
unit_file_changes_add(changes, n_changes, -EUCLEAN, dst, NULL);
r = -EUCLEAN;
if (!unit_name_is_valid(dst, valid_dst_type)) {
/* Generate a proper error here: EUCLEAN if the name is generally bad,
* EIDRM if the template status doesn't match. */
if (unit_name_is_valid(dst, UNIT_NAME_ANY)) {
unit_file_changes_add(changes, n_changes, -EIDRM, dst, n);
r = -EIDRM;
} else {
unit_file_changes_add(changes, n_changes, -EUCLEAN, dst, NULL);
r = -EUCLEAN;
}
continue;
}