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aliasd, aliasd_niff - Cluster alias daemons
The aliasd daemon handles the proxy ARP and gated configuration of alias
host and network routes over both common and virtual subnets. By default,
the daemon will advertise alias routes over any broadcast capable
interfaces on the system, with the exception of the cluster interconnect
and loopback interfaces.
By default, each cluster member runs an aliasd daemon, which is started
from an init script linked to /sbin/rc3.d. The daemon is started at boot
time and, under normal circumstances, runs until the member shuts down.
Only one daemon runs on each cluster member. If you attempt to start a
second daemon, it will exit. Each member's daemon creates a gated
configuration file for that member, /etc/gated.conf.membern. By default,
aliasd restarts gated specifying /etc/gated.conf.membern as gated's
The aliasd daemon forks a child process and executes /usr/sbin/aliasd_niff.
The aliasd_niff daemon creates an EVM connection and subscribes for all
NIFF events. It monitors EVM looking for events related to interfaces used
by aliasd; for example, to check whether an interface used to advertise
aliases becomes unusable. If aliasd_niff sees such an event, it notifies
aliasd. If an interface comes up or goes down, the parent can modify
/etc/gated.conf.membern and stop/restart the gated daemon.
Note that during a normal boot of a cluster member, if only one other
member is up, that member might stop and restart gated without there being
a real interface failure. The cluster interconnect interface on a single-
member cluster is inactive from NIFF's perspective. When another cluster
member boots, the interface changes state, the parent aliasd is notified,
and it responds by stopping and starting gated.
The aliasd daemon also arbitrates the election of proxy ARP masters. For
each alias advertised by proxy ARP, only one cluster member at a time can
act as the proxy ARP master for that alias. The cluster aliasd daemons use
DLM locks to negotiate proxy ARP masters as required at startup, and, if a
current master become unavailable, to elect a new master.
The cluamgr command provides options that affect daemon behavior. Under
normal circumstances, you should not use the cluamgr -r options to modify
the daemon's behavior. The daemon is designed to operate correctly from the
startup file; it gets information from the cluster alias subsystem and
automatically updates routes as needed. Do not stop and restart the daemon
without good reason. The cluamgr options are provided in case you need to
modify daemon behavior; for example, to help diagnose a problem with alias
routing on a cluster member. A site that uses static routing or a routing
protocol other than the Routing Information Protocol (RIP) can use the
nogated routing option to prohibit aliasd from restarting gated with
/etc/gated.conf.membern as its configuration file. See cluamgr(8) for
information on the nogated routing option.
The aliasd daemon exits with one of the following values:
1 Failure: unknown flag or segmentation violation.
-1 Cannot obtain cluster member ID.
Member-specific gated configuration file created by aliasd.
Contains configuration information for the cluster alias
UNIX domain socket used by the cluamgr command to pass options to
the aliasd daemon.
Commands: cluamgr(8), gated(8)
Miscellaneous: niff(7), EVM(5)
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