dev-manual: note on using journald without syslog

journald is not a syslog provider, so using journald exclusively amounts
to just preventing a syslog provider from being specified on a system
where journald is active.

Various spots where this has popped up:
* https://stackoverflow.com/q/48746397
* https://lists.yoctoproject.org/g/yocto/topic/82883035#53548

(From yocto-docs rev: aba38d5dc2db708ed6e8fc6dca4d869fe7fe855c)

Signed-off-by: Nicholas Sielicki <nicholas.sielicki@legrand.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/documentation/dev-manual/common-tasks.rst b/documentation/dev-manual/common-tasks.rst
index ca3fbc856a..9d4aaa5a67 100644
--- a/documentation/dev-manual/common-tasks.rst
+++ b/documentation/dev-manual/common-tasks.rst
@@ -7910,6 +7910,20 @@ image cannot use this package group. However, it can install SysVinit
 and the appropriate packages will have support for both systemd and
 SysVinit.
 
+Using systemd-journald without a traditional syslog daemon
+----------------------------------------------------------
+
+Counter-intuitively, ``systemd-journald`` is not a syslog runtime or provider,
+and the proper way to use systemd-journald as your sole logging mechanism is to
+effectively disable syslog entirely by setting these variables in your distribution
+configuration file::
+
+   VIRTUAL-RUNTIME_syslog = ""
+   VIRTUAL-RUNTIME_base-utils-syslog = ""
+
+Doing so will prevent ``rsyslog`` / ``busybox-syslog`` from being pulled in by
+default, leaving only ``journald``.
+
 Selecting a Device Manager
 ==========================