Last Change: 2018-09-07, 16:50
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ucarp — Automatic IP failover
ucarp [-i, −−interface=INTERFACE] [-s, −−srcip=IPADDRESS]
[-v, −−vhid=VHID] [-p, −−pass=PASSWORD] [-o, −−passfile=PASSFILE]
[-P, −−preempt] [-n, −−neutral] [-a, −−addr=IPADDR] [-h, −−help]
[-b, −−advbase=SECS] [-k, −−advskew=SKEW] [-u, −−upscript=SCRIPT]
[-d, −−downscript=SCRIPT] [-r, −−deadratio=RATIO] [-z, −−shutdown]
[-B, −−daemonize] [-f, −−facility=FACILITY] [-x, −−xparam PARAM] [-S, −−ignoreifstate]
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.
ucarp supports the following command line options:
-i INTERFACE −−interface=INTERFACE
The network interface to bind to.
-s IPADDRESS −−srcip=IPADDRESS
The persistent source address, (real IP), associated with this interface.
-v VHID −−vhid=VHID
The id of the virtual server [1-255].
-p PASSWORD −−pass=PASSWORD
The shared password, (this gets encrypted and is not sent in the clear).
-o PASSFILE −−passfile=PASSFILE
File to read the shared password from. The file specified should contain the password on the first line of the file.
-P −−preempt
Turn on preemptive failover. This causes an instance of ucarp to assume master status right immediately.
-n −−neutral
Do not run the downscript on startup when the initial state is backup.
-a IPADDRESS −−addr=IPADDRESS
The IP address of the virtual server.
|
-h −−help |
Display a brief summary of the command line options. |
-b SECONDS −−advbase=SECONDS
Interval in seconds that advertisements will occur, (defaults to 1 second).
-k SKEW −−advskew=SKEW
Advertisement skew [1-255], (defaults to 0).
-u COMMAND −−upscript=COMMAND
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 COMMAND −−downscript=COMMAND
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 −−deadratio=RATIO
Ratio used by the backup to determine how long to wait for an unresponsive master before considering it dead.
-z −−shutdown
Use of this command causes the command specified by the −d argument to be invoked when ucarp shuts down.
-B −−daemonize
Causes ucarp to detach from the terminal and run in the background as a daemon.
-f −−facility
Set the syslog facility, defaults to daemon.
-x PARAMETER −−xparam=PARAMETER
Specify an extra parameter to be supplied to the up/down scripts.
-S −−ignoreifstate
Ignore unplugged network cables. This option is useful when ucarp nodes are connected with a crossover cable. Without this option the master will transition to backup when the other node is powered down, as it no longer has a link (NO-CARRIER).
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.
ucarp −i eth0 −s 10.1.1.10 −v 10 −p secret −a 10.1.1.252 \
−−upscript=/etc/vip-up.sh −−downscript=/etc/vip-down.sh −P
The backup might be configured something like this.
ucarp −i eth0 −s 10.1.1.11 −v 10 −p secret −a 10.1.1.252 \
−−upscript=/etc/vip-up.sh −−downscript=/etc/vip-down.sh
A machine with a real IP of 192.168.1.19 is the preferred master for a virtual IP of 10.1.12.7, broadcasts are sent every 5 seconds.
ucarp −b 5 −s 192.168.1.19 −v 27 −p badpass −a 10.1.12.7 \
-u /etc/vip-up.sh −d /etc/vip-down.sh −z
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).
ucarp −b 5 −k 50 −s 192.168.1.20 −v 27 −p badpass −a 10.1.12.7 \
-u /etc/vip-up.sh −d /etc/vip-down.sh −z
ucarp was written by Frank Denis, <j AT ucarp DOT org>.
This manual page was written by Eric Evans <eevans AT debian DOT org> 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 or 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.