Bug 101570

Summary:	On systemd systems, symlink dbus machine ID to /etc/machine-id
Product:	dbus	Reporter:	Simon McVittie <smcv>
Component:	core	Assignee:	Simon McVittie <smcv>
Status:	RESOLVED FIXED	QA Contact:	D-Bus Maintainers <dbus>
Severity:	enhancement
Priority:	medium	Keywords:	patch
Version:	git master
Hardware:	Other
OS:	All
Whiteboard:	review+
i915 platform:		i915 features:
Bug Depends on:
Bug Blocks:	101354
Attachments:	Install a systemd tmpfiles.d snippet to create /var/lib/dbus/machine-id Install a systemd tmpfiles.d snippet to create /var/lib/dbus/machine-id

Description Simon McVittie 2017-06-23 16:22:35 UTC

Created attachment 132166 [details] [review]
Install a systemd tmpfiles.d snippet to create  /var/lib/dbus/machine-id

On systemd systems, /etc/machine-id is guaranteed to exist and has
the same format as the D-Bus machine ID. The major D-Bus implementations
read /etc/machine-id if it exists, but some less up-to-date
implementations still only read /var/lib/dbus/machine-id. We can be
nice to those implementations by ensuring /var/lib/dbus/machine-id
is a symlink; this way, the two files can never get out of sync.

---

We do this in Debian already, as a local packaging change. It supersedes this Ubuntu patch:

dbus (1.8.12-1ubuntu4) vivid; urgency=medium

  * debian/patches/ensure-dbus-machine-id.patch:
    - ensure that we have /var/lib/dbus/machine-id on user's system as some
      third-parties application relies on that file. It will only copy
      /etc/machine-id the file is not present already.

 -- Didier Roche <didrocks@ubuntu.com>   Thu, 19 Mar 2015 15:19:02 +0100

https://launchpadlibrarian.net/200646138/dbus_1.8.12-1ubuntu3_1.8.12-1ubuntu4.diff.gz

which ran dbus-uuidgen in the systemd unit (I preferred to use tmpfiles).

I did this in the Bug #101354 branch because in that branch, I also create ${runstatedir}/dbus/containers/ owned by messagebus in the tmpfiles snippet, so that the system bus can put its sockets there. If I try to do both things in the tmpfiles snippet without a dependency relationship, they'll conflict.

Comment 1 Simon McVittie 2017-06-23 16:23:47 UTC

Comment on attachment 132166 [details] [review]
Install a systemd tmpfiles.d snippet to create  /var/lib/dbus/machine-id

Review of attachment 132166 [details] [review]:
-----------------------------------------------------------------

::: bus/Makefile.am
@@ +319,4 @@
>  	systemd-user/dbus.service.in \
>  	systemd-user/dbus.socket.in \
>  	sysusers.d/dbus.conf.in
> +	tmpfiles.d/dbus.conf.in

This is clearly wrong - needs more backslashes.

Comment 2 Simon McVittie 2017-06-26 19:06:15 UTC

Created attachment 132263 [details] [review]
Install a systemd tmpfiles.d snippet to create  /var/lib/dbus/machine-id

On systemd systems, /etc/machine-id is guaranteed to exist and has
the same format as the D-Bus machine ID. The major D-Bus implementations
read /etc/machine-id if it exists, but some less up-to-date
implementations still only read /var/lib/dbus/machine-id. We can be
nice to those implementations by ensuring /var/lib/dbus/machine-id
is a symlink; this way, the two files can never get out of sync.

---

Correct Makefile syntax

Comment 3 Philip Withnall 2017-06-27 19:11:06 UTC

Comment on attachment 132263 [details] [review]
Install a systemd tmpfiles.d snippet to create  /var/lib/dbus/machine-id

Review of attachment 132263 [details] [review]:
-----------------------------------------------------------------

r+

Comment 4 Simon McVittie 2017-06-29 13:02:26 UTC

Thanks, fixed in git for 1.11.14.

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