Use this documentation with care! It describes the heavily outdated version 5, which was actively developed around 2010 and is considered dead by the rsyslog team for many years now.

This documentation reflects the latest update of the previously existing (now removed) v5-stable branch. It describes the 5.10.2 version, which was never released. As such, it contains some content that does not apply to any released version.

To obtain the doc that properly matches your installed v5 version, obtain the doc set from your distro. Each version of rsyslog contained the version that exactly matches it.

As general advise, it is strongly suggested to upgrade to the current version supported by the rsyslog project. The current version can always be found on the right-hand side info box on the rsyslog web site.

Note that there is no rsyslog community support available for this heavily outdated version. If you need to stick with it, please ask your distribution for support.

imrelp: RELP Input Module

Provides the ability to receive syslog messages via the reliable RELP protocol. This module requires librelp to be present on the system. From the user’s point of view, imrelp works much like imtcp or imgssapi, except that no message loss can occur.

Clients send messages to the RELP server via omrelp.

Author: Rainer Gerhards

Configuration Directives

InputRELPServerRun <port>

Starts a RELP server on selected port

Caveats/Known Bugs

  • With the currently supported relp protocol version, a minor message duplication may occur if a network connection between the relp client and relp server breaks after the client could successfully send some messages but the server could not acknowledge them. The window of opportunity is very slim, but in theory this is possible. Future versions of RELP will prevent this.
  • rsyslogd may lose a few messages if rsyslog is shutdown while a network conneciton to the server is broken and could not yet be recovered. Future version of RELP support in rsyslog will prevent that.
  • Please note that both scenarios also exists with plain tcp syslog. RELP, even with the small nits outlined above, is a much more reliable solution than plain tcp syslog and so it is highly suggested to use RELP instead of plain tcp.
  • To obtain the remote system’s IP address, you need to have at least librelp 1.0.0 installed. Versions below it return the hostname instead of the IP address.


This sets up a RELP server on port 20514.

$ModLoad imrelp # needs to be done just once
$InputRELPServerRun 20514