There are sometimes users who put unit files in a location that is inaccessible
when systemd starts although they are not found and thus not started because
the corresponding mount units have not activated yet.
There is already a warning for such issue in man 8 systemctl:
link PATH...
...<snip>...
The file system where
the linked unit files are located must be accessible
when systemd is started (e.g. anything underneath /home
or /var is not allowed, unless those directories are
located on the root file system).
However, it looks that it's difficult to find the warning because introductory
users typically doesn't know systemctl link.
Although there is a description in UNIT FILE LOAD PATH pointing to systemctl
link, symlink is now not explicitly mentioned there and thus users doesn't
easily get aware of they should read it.
To deal with this, let's describe "symlink" and "systemctl link" more
explicitly in UNIT FILE LOAD PATH.
When wrong element types are used, directives are sometimes placed in the wrong
section. Also, strip part of text starting with "'", which is used in a few
places and which is displayed improperly in the index.
Discussed in #13743, the -.service semantic conflicts with the
existing root mount and slice names, making this feature not
uniformly extensible to all types. Change the name to be
<type>.d instead.
Updating to this format also extends the top-level dropin to
unit types.
We want users to use Wants, but we'd describe Requires first and ask users to
look for Wants instead. While at it, let's split the wall of text into sensible
paragraphs: syntax first, followed by semantics and longer description, and
finally hints and comparison to other configuration items last.
We slowly added many many conditions over the years, and the text became
very hard to read, because all the terms were squished in one <termitem>.
This rearragnes the text into a new subsection, with minimal grammar changes
and removal of repetitions.
The description of Alias= wasn't incorrect, but it sounded like Alias= creates
a different type of dependency, while it's just a glorified way to create
symlinks. Also recommend 'preset' in addition to 'enable'.
Describe .wants/.requires dirs as equals, without implying that the [Install]
section can only be used for .wants.
The text was partially out of date (systemd-networkd.service now creates as
alias in /etc, not /usr/lib, let's just not say anything about the full path).
Before only one comparison was allowed. Let's make this more flexible:
ConditionKernelVersion = ">=4.0" "<=4.5"
Fixes#12881.
This also fixes expressions like "ConditionKernelVersion=>" which would
evaluate as true.
