FixedRandomDelay=yes will use
`siphash24(sd_id128_get_machine() || MANAGER_IS_SYSTEM(m) || getuid() || u->id)`,
where || is concatenation, instead of a random number to choose a value between
0 and RandomizedDelaySec= as the timer delay.
This essentially sets up a fixed, but seemingly random, offset for each timer
iteration rather than having a random offset recalculated each time it fires.
Closes#10355
Co-author: Anita Zhang <the.anitazha@gmail.com>
Primarily:
1. Mention that we prefer if return parameters carry "ret_" as prefix in
their name
2. Clarify that debug-level logging is always OK, and irrelevant to when
deciding whether a function is logging or non-logging.
We have three somewhat separate ideas: what the directory is for, what $TMPDIR is for, and security considerations.
Let's use paragraphs.
Also, conjunctions in titles aren't capitalized usually.
It makes little sense to make the boundary between systemd and user guids
configurable. Nevertheless, a completely fixed compile-time define is not
enough in two scenarios:
- the systemd_uid_max boundary has moved over time. The default used to be
500 for a long time. Systems which are upgraded over time might have users
in the wrong range, but changing existing systems is complicated and
expensive (offline disks, backups, remote systems, read-only media, etc.)
- systems are used in a heterogenous enviornment, where some vendors pick
one value and others another.
So let's make this boundary overridable using /etc/login.defs.
Fixes#3855, #10184.
