/usr/src/xtables-addons-2.6/extensions/libxt_LOGMARK.man is in xtables-addons-dkms 2.6-1.
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The LOGMARK target will log packet and connection marks to syslog.
.TP
\fB\-\-log\-level\fR \fIlevel\fR
A logging level between 0 and 8 (inclusive).
.TP
\fB\-\-log\-prefix\fR \fIstring\fR
Prefix log messages with the specified prefix; up to 29 bytes long, and useful
for distinguishing messages in the logs.
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