There are currently two config directives available that allow a
config file to incorporate the contents of other files: &include
and &merge. Both allow a reference to either a file or a
directory. They differ in how segregated the file's contents are
considered to be.
The &include directive treats each file as more distinct, with
each one inheriting the defaults of the parent file, starting the
parameter parsing as globals/defaults, and leaving the defaults
unchanged for the parsing of the rest of the parent file.
The &merge directive, on the other hand, treats the file's
contents as if it were simply inserted in place of the directive,
and thus it can set parameters in a module started in another
file, can affect the defaults for other files, etc.
When an &include or &merge directive refers to a directory, it
will read in all the *.conf or *.inc files (respectively) that
are contained inside that directory (without any recursive
scanning), with the files sorted into alpha order. So, if you
have a directory named "rsyncd.d" with the files "foo.conf",
"bar.conf", and "baz.conf" inside it, this directive:
&include /path/rsyncd.d
would be the same as this set of directives:
&include /path/rsyncd.d/bar.conf
&include /path/rsyncd.d/baz.conf
&include /path/rsyncd.d/foo.conf
except that it adjusts as files are added and removed from the
directory.
The advantage of the &include directive is that you can define
one or more modules in a separate file without worrying about
unintended side-effects between the self-contained module files.
The advantage of the &merge directive is that you can load config
snippets that can be included into multiple module definitions,
and you can also set global values that will affect connections
(such as motd file), or globals that will affect other include
files.
For example, this is a useful /etc/rsyncd.conf file:
port = 873
log file = /var/log/rsync.log
pid file = /var/lock/rsync.lock
&merge /etc/rsyncd.d
&include /etc/rsyncd.d
This would merge any /etc/rsyncd.d/*.inc files (for global values
that should stay in effect), and then include any
/etc/rsyncd.d/*.conf files (defining modules without any global-
value cross-talk).
