unit-name: introduce "strict" mode for unit name mangling by mrc0mmand · Pull Request #42638 · systemd/systemd

mrc0mmand · 2026-06-17T12:33:21Z

unit_name_mangle_with_suffix() is quite benevolent by default and allows
the unit to "transition" into a different unit type than what's
requested via its suffix argument. For example, calling
unit_name_mangle_with_suffix() with "/foo/bar" as a unit name and
".service" as a suffix would give you "foo-bar.mount", without any
warning or error.

This could then lead to a quite confusing errors in certain situations:

~# systemd-run --remain-after-exit --unit /foo/bar true
Failed to start transient service unit: Cannot set property RemainAfterExit, or unknown property.

Given we can't change the default behaviour of
unit_name_mangle_with_suffix() as some parts of systemd already depend
on its "benevolence" (like systemctl), let's introduce a new flag -
UNIT_NAME_MANGLE_STRICT - that checks if the mangled/resolved unit
name's suffix matches the requested one and errors out if not.

With the flag used throughout systemd-run's code, the error in the above
case is now a bit more clear:

~# build/systemd-run --remain-after-exit --unit /foo/bar true
Path "/foo/bar" resolves to unit type "mount", but "service" is expected as unit.
Failed to mangle unit name: Invalid argument

Resolves: #39996

github-actions · 2026-06-17T12:35:06Z

yuwata

LGTM.

unit_name_mangle_with_suffix() is quite benevolent by default and allows the unit to "transition" into a different unit type than what's requested via its suffix argument. For example, calling unit_name_mangle_with_suffix() with "/foo/bar" as a unit name and ".service" as a suffix would give you "foo-bar.mount", without any warning or error. This could then lead to a quite confusing errors in certain situations: ~# systemd-run --remain-after-exit --unit /foo/bar true Failed to start transient service unit: Cannot set property RemainAfterExit, or unknown property. Given we can't change the default behaviour of unit_name_mangle_with_suffix() as some parts of systemd already depend on its "benevolence" (like systemctl), let's introduce a new flag - UNIT_NAME_MANGLE_STRICT - that checks if the mangled/resolved unit name's suffix matches the requested one and errors out if not. With the flag used throughout systemd-run's code, the error in the above case is now a bit more clear: ~# build/systemd-run --remain-after-exit --unit /foo/bar true Path "/foo/bar" resolves to unit type "mount", but "service" is expected as unit. Failed to mangle unit name: Invalid argument Resolves: systemd#39996

mrc0mmand added the claude-review label Jun 17, 2026

github-actions Bot added util-lib tests run please-review PR is ready for (re-)review by a maintainer labels Jun 17, 2026