zephyrd - Zephyr server daemon

/usr/etc/zephyrd [ -d ]

zephyrd is the central server for the Zephyr Notification System. It maintains a location database of all currently logged-in users, and a subscription database for each user's Zephyr clients.

zephyrd communicates with daemons running on other Zephyr server hosts, to provide a reliable service.

While running, any unusual conditions are recorded via syslog(3) to facility local6 at various levels. The -d option enables logging of additional debugging information.

When a zephyrd is executed, it requests a list of server machines from Hesiod and initializes its state from any zephyrds executing on the other known servers. This initialization is only performed after the zephyrds have authenticated themselves to each other via Kerberos. The server then enters a dispatch loop, servicing requests from clients and other servers.

SIGUSR1 enables logging of additional debugging information.

SIGUSR2 disables the logging of additional debugging information.

SIGHUP causes zephyrd to re-read the default subscription file and to re-query Hesiod about valid peers. Any peers which are not responding and no longer mentioned in Hesiod are flushed; any peers not previously named by Hesiod are added.

SIGINT and SIGTERM cause zephyrd to gracefully shut down.

SIGFPE causes zephyrd to dump the location and subscription databases to /var/tmp/zephyr.db in an ASCII format.

Certain notice classes are restricted by the Zephyr server. Each such class has access control lists enumerating who may transmit (xmt-*.acl) or subscribe to that particular class. Subscriptions may be restricted either absolutely (sub-*.acl files), or by instance restrictions. iws-*.acl files control subscriptions to wildcarded instances. iui-*.acl files control subscriptions to instances which are not the Kerberos principal identity of the subscriber. If an access control list of a given type is absent, there is no restriction of that type on the class, except that any notices of the class must be authenticated. The class registry lists all classes which are restricted.

/usr/athena/lib/zephyr/class-registry.acl:

List of classes which are restricted

/usr/athena/lib/zephyr/iws-*.acl:

Access Control Lists for instance-wildcard restrictions

/usr/athena/lib/zephyr/iui-*.acl:

Access Control Lists for instance-identity restrictions

/usr/athena/lib/zephyr/sub-*.acl:

Access Control Lists for subscribing

/usr/athena/lib/zephyr/xmt-*.acl:

Access Control Lists for transmitting

/usr/athena/lib/zephyr/srvtab:

Kerberos Service keys

/usr/athena/lib/zephyr/ztkts:

Current Kerberos tickets for exchange with other servers

/usr/tmp/zephyr.db:

File containing an ASCII dump of the database.

The current implementation of the Zephyr server (zephyrd(8)) makes no distinction between realm-announced, net-visible and net-announced exposure levels.

zephyr(1), zhm(8), kerberosintro(1), hesiod(3), access_control_lists(?), syslog(3)

Athena Technical Plan, Sections E.4.1 (Zephyr Notification Service) and E.2.1 (Kerberos Authentication and Authorization System)

John T. Kohl, MIT Project Athena and Digital Equipment Corporation

Copyright (c) 1987,1988 by the Massachusetts Institute of Technology. All Rights Reserved.

zephyr(1) specifies the terms and conditions for redistribution.