I came across this one Debian Linux installation (6.0.6), and examining its /etc/rsyslog.conf, I see configuration lines like this:
auth,authpriv.* /var/log/auth.log *.*;auth,authpriv.none -/var/log/syslog I can't find anything about prepending dashes to the file action in rsyslog.conf(5), and what the meaning of it might be, and would like to know what they actually do.
Googled this a bit more, and found this.
In essence, it means to not synchronize the log file to disk every time there is a write, if synchronization behavior is on by default.
It is stated that since v3 the default behavior is not sync, and it's possible to change this by specifying "$ActionFileEnableSync on/off".
To add a bit more context, the "Configuration » Actions" documentation page describes the significance of prefixing output filenames with a - (U+002D "HYPHEN-MINUS"):
You may prefix each entry with the minus “-‘’ sign to omit syncing the file after every logging.
However, that page does not mention the $ActionFileEnableSync configuration statement, nor that it defaults to off as of v3.12.4 (released on 2008-03-25, according to the ChangeLog).
EDIT: I originally (mis)read the page @Pawel linked to, missing the relevant remark inside a parenthetical there:
Rsyslogd tries to keep as compatible to stock syslogd as possible. As such, it retained stock syslogd’s default of syncing every file write if not specified otherwise (by placing a dash in front of the output file name).
