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System Administration Commandssac(1M)


 sac - service access controller


 sac -t sanity_interval



The Service Access Controller (SAC) is the overseer of the server machine. It is started when the server machine enters multiuser mode. The SAC performs several important functions as explained below.

Customizing the SAC Environment


When sac is invoked, it first looks for the per-system configuration script /etc/saf/_sysconfig. sac interprets _sysconfig to customize its own environment. The modifications made to the SAC environment by _sysconfig are inherited by all the children of the SAC. This inherited environment may be modified by the children.

Starting Port Monitors


After it has interpreted the _sysconfig file, the sac reads its administrative file /etc/saf/_sactab. _sactab specifies which port monitors are to be started. For each port monitor to be started, sac forks a child (see fork(2)) and creates a utmpx entry with the type field set to LOGIN_PROCESS. Each child then interprets its per-port monitor configuration script /etc/saf/pmtag/_config , if the file exists. These modifications to the environment affect the port monitor and will be inherited by all its children. Finally, the child process execs the port monitor, using the command found in the _sactab entry. (See sacadm; this is the command given with the -c option when the port monitor is added to the system.)

Polling Port Monitors to Detect Failure


The -t option sets the frequency with which sac polls the port monitors on the system. This time may also be thought of as half of the maximum latency required to detect that a port monitor has failed and that recovery action is necessary.

Administrative functions


The Service Access Controller represents the administrative point of control for port monitors. Its administrative tasks are explained below.

When queried (sacadm with either -l or -L), the Service Access Controller returns the status of the port monitors specified, which sacadm prints on the standard output. A port monitor may be in one of six states:

The port monitor is currently running and is accepting connections. See sacadm(1M) with the -e option.
The port monitor is currently running and is not accepting connections. See sacadm with the -d option, and see NOTRUNNING, below.
The port monitor is in the process of starting up. STARTING is an intermediate state on the way to ENABLED or DISABLED.
The port monitor was unable to start and remain running.
The port monitor has been manually terminated but has not completed its shutdown procedure. STOPPING is an intermediate state on the way to NOTRUNNING.
The port monitor is not currently running. (See sacadm with -k.) This is the normal "not running" state. When a port monitor is killed, all ports it was monitoring are inaccessible. It is not possible for an external user to tell whether a port is not being monitored or the system is down. If the port monitor is not killed but is in the DISABLED state, it may be possible (depending on the port monitor being used) to write a message on the inaccessible port telling the user who is trying to access the port that it is disabled. This is the advantage of having a DISABLED state as well as the NOTRUNNING state.

When a port monitor terminates, the SAC removes the utmpx entry for that port monitor.

The SAC receives all requests to enable, disable, start, or stop port monitors and takes the appropriate action.

The SAC is responsible for restarting port monitors that terminate. Whether or not the SAC will restart a given port monitor depends on two things:

  • The restart count specified for the port monitor when the port monitor was added by sacadm; this information is included in /etc/saf/pmtag/_sactab.
  • The number of times the port monitor has already been restarted.



sac uses pam(3PAM) for session management. The PAM configuration policy, listed through /etc/pam.conf, specifies the session management module to be used for sac. Here is a partial pam.conf file with entries for sac using the UNIX session management module.

sac  session   required

If there are no entries for the sac service, then the entries for the "other" service will be used.


-t sanity_interval
Sets the frequency (sanity_interval) with which sac polls the port monitors on the system.





See attributes(5) for descriptions of the following attributes:




pmadm(1M), sacadm(1M), fork(2) pam(3PAM), pam.conf(4), attributes(5), pam_authtok_check(5), pam_authtok_get(5), pam_authtok_store(5), pam_dhkeys(5), pam_passwd_auth(5), pam_unix(5), pam_unix_account(5), pam_unix_auth(5), pam_unix_session(5)



The pam_unix(5) module might not be supported in a future release. Similar functionality is provided by pam_authtok_check(5), pam_authtok_get(5), pam_authtok_store(5), pam_dhkeys(5), pam_passwd_auth(5), pam_unix_account(5), pam_unix_auth(5), and pam_unix_session(5).

SunOS 5.9Go To TopLast Changed 11 Dec 2001

Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.