ucarp allows a pair of hosts to share common IP addresses in
order to provide automatic failover of an address from one machine to
another. It is a portable userland implementation of the secure and
patent-free Common Address Redundancy Protocol, (CARP), OpenBSD's
alternative to VRRP.
OPTIONS
ucarp supports the following command line options:
"-i
The network interface to bind to.
"-s
The persistent source address, (real IP), associated
with this interface.
"-v
The id of the virtual server [1-255].
"-p
The shared password, (this gets encrypted and is not
sent in the clear).
"-P
Turn on preemptive failover. This causes an instance
of ucarp to take over master status right away.
"-a
The IP address of the virtual server.
"-h
Display a brief summary of the command line
options.
"-b
Interval in seconds that advertisements will occur,
(defaults to 1 second).
"-k
Advertisement skew [1-255], (defaults to 0).
"-u
Specifies the command to run after ucarp has
successfully become master, the interface name gets passed
as an argument. Typically a script used to bring up the
virtual address, log the result, add routes, clear arp
cache entries, etc.
"-d
Specifies the command that is run after ucarp has
transitioned to the backup state, the interface name is passed
as an argument. This is typically a script used to bring down
the virtual interface, log the action, remove routes,
etc.
"-r
Ratio used by the backup to determine how long to
wait for an unresponsive master before considering it dead.
"-z
Use of this command causes the command specified by
the -d argument to be invoked when ucarp shuts down.
"-B
Causes ucarp to detach from the terminal and
run in the background as a daemon.
"-f
Set the syslog facility, defaults to daemon.
EXAMPLES
A host with a real IP of 10.1.1.10 configured to be the master
in a preemptive configuration with a virtual IP of 10.1.1.252.
The hot standby with an IP of 192.168.1.20 uses the following
command, (note the advskew of 50 putting it at a disadvantage and making
the first machine preferred).
This manual page was written by Eric Evans <eevans@sym-link.com>
for the Debian system (but may be used by others). Permission is
granted to copy, distribute and/or modify this document under
the terms of the GNU General Public License, Version 2 any
later version published by the Free Software Foundation.
On Debian systems, the complete text of the GNU General Public
License can be found in /usr/share/common-licenses/GPL.
