
Troubleshooting Systemd with SystemTap - andrenth
https://blog.janestreet.com/troubleshooting-systemd-with-systemtap/
======
JdeBP
The centralized journal daemon and Desktop Bus broker with a single Desktop
Bus are two of the major weaknesses in the systemd architecture, sources of
problems as varied as log floods affecting unrelated services, journald
(originally) taking everything with it when it died (a failure to understand
the lessons of daemontools, also explaining why originally every service was
proofed against SIGPIPE), and the Desktop Bus Death Rattle.

* [http://jdebp.uk./FGA/dbus-death-rattle.html](http://jdebp.uk./FGA/dbus-death-rattle.html)

One does not need SystemTap to see the mount unit problems, never fear. As the
article notes, near the bottom, the behaviour is documented in the
systemd.mount manual page; and one can look at the Desktop Bus traffic with
busctl monitor.

But again, this is a failure to learn the lessons of previous softwares; in
particular the lessons of the many softwares that do/did data updates over
limited bandwidth channels. From everything, from redrawing the screen in a
full-screen TUI program like vi, through sending the Fidonet nodelist around
the world, to doing quick tape backups, one learns the lesson of _sending just
the diffs_. As the author noted, it seems daft for systemd-logind to be told,
again, all about the 1999 of the 2000 mount points that _have not changed_.

The sad thing is that systemd-logind isn't even interested in mount units. It
registers an interest in all unit properties change announcements, but is only
really interested in the properties of session and "user" slice units.

