usbmuxd: create the usbmux user the udev rule requires

usbmuxd ships 39-usbmuxd.rules, which starts the daemon when an Apple
device appears:

  ACTION=="add", ..., OWNER="usbmux", ENV{SYSTEMD_WANTS}="usbmuxd.service"

The recipe never creates that account. Up to systemd v257 udev only
logged a warning and the rest of the line still ran. systemd a1ee55e3c9
("udev-rules: ignore OWNER=/GROUP= with unknown user/group", first
released in v258) makes udev drop the whole rule line instead, so
SYSTEMD_WANTS is never applied and usbmuxd is never started when a
device is plugged in.

Creating the account is what the rule already expects, and it preserves
the intent of the systemd change: that change guards against a rule
naming a nonexistent user silently clearing a valid earlier ownership
assignment, and with the account present there is no nonexistent user.
Removing OWNER= from the rule would evade that check instead of
satisfying it. The daemon still runs as root, so nothing else changes.

Also ship a sysusers.d fragment. Systems that modified a user or
password at runtime carry a copied-up /etc/passwd in a writable /etc,
which masks an account added at image build time even after an update;
systemd-sysusers recreates it there. The uid may then differ, but the
udev rule resolves the account by name and the daemon runs as root, so
only the name matters.

Distros that keep /etc on persistent storage may also need
systemd-sysusers to actually run on boot; that is outside the scope of
this recipe.

Signed-off-by: Eric Chiang <ericyunlinchiang@gmail.com>
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
(cherry picked from commit 5b4d5deac5bbbd286d43a6f6a3d1f8722bdfa8aa)
Change-Id: If778197c7db00fb14284678dd1b1b0e0b2423cff
Signed-off-by: Eric Chiang Quanta <Eric.Chiang@quantatw.com>

0 files changed, 0 insertions, 0 deletions