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Subsections


The Shutown Sequence and its Discontents


Shutdown Sequence

If you experienced so problems with the testing procedures, or if you are porting apcupsd to another system, or you are simply curious, you may want to know exactly what is going on during the shutdown process.

The shutdown sequence is as follows:

The above code must be inserted as late as possible in the halt script. On many systems, such as Red Hat, all the disk drives were unmounted, then remounted read-only, thus permitting access to the /etc files and the apcupsd executable. If your system does not explicitly remount the disks, you must remount them in read-only mode in the code that you add. Examples of code fragments that do this can be found in the distributions/suse subdirectory of the source.

If you are not able to insert the above code in your halt script because there is no halt script, or because your halt script calls the init program as some Unix systems do, you can either just forget about powering off the UPS, which means that your machine will not automatically reboot after a power failure, or there is yet another alternative, though not at all as satisfying as inserting code in the halt script.

Only if you cannot insert the appropriate code in the halt script, when you start apcupsd, normally from the /etc/rc.d/init.d/apcupsd script, use the --kill-on-powerfail option. This will cause apcupsd to program the UPS to shutoff the power just before it (apcupsd) does the system shutdown. Please note that this is not the most ideal solution. Read on to understand why.

A very important consideration is that you must set the EEPROM in your UPS so that it waits a sufficient time for the system to halt before it shuts off the UPS power. The current value as well as the permitted values for your UPS can be determined by executing:

     apcaccess eeprom

The output should look something like the following:

     apcaccess eeprom
     
     Valid EPROM values for the SMART-UPS 1000
     
                            Config        Current  Permitted
     Description              Directive     Value    Values
     ===================================================================
     Upper transfer voltage   HITRANSFER    253      253 264 271 280
     Lower transfer voltage   LOTRANSFER    196      196 188 208 204
     Return threshold         RETURNCHARGE  0        00 15 50 90
     Output voltage on batts  OUTPUTVOLTS   230      230 240 220 225
     Sensitivity              SENSITIVITY   H        H M L L
     Low battery warning      LOWBATT       2        02 05 07 10
     Shutdown grace delay     SLEEP         20       020 180 300 600
     Alarm delay              BEEPSTATE     0        0 T L N
     Wakeup delay             WAKEUP        0        000 060 180 300
     Self test interval       SELFTEST      336      336 168 ON  OFF

The line of interest for you is the Shutdown grace delay, which can be changed using the SLEEP (see SLEEP <set sleep delay>) directive in your apcupsd.conf file. The default value is 20 seconds, but generally, you can set it to 180, 300, or 600 seconds depending on your UPS. See the EEPROM (see Configuring Your EEPROM) this manual for further details on how to change this EPROM value.

If you use the --kill-on-powerfail option, you run the risk of having the computer power cut before the system has shutdown. Even if the grace period is rather long, if something goes wrong in the shutdown, well, it is up to you to decide.

If apcupsd has successfully shutdown your computer and powered off the UPS during a power outage, you can control whether or not your computer is automatically rebooted when the power returns.

The UPS contains two internal EPROM values that determine when it will restore power to your computer after a full power shutdown. They are the RETURNCHARGE (see RETURNCHARGE <min_ batt_ charge level>) percentage and the WAKEUP (see WAKEUP <set wakeup delay>) delay. Briefly, the RETURNCHARGE specifies what percentage charge the battery must have before the power is restored. Higher values are recommended in regions where the power goes up and down frequently. The WAKEUP delay is a simple time delay. Most sites will have both of these at zero, or perhaps the RETURNCHARGE set to 15. Please follow the links to the Configuration section of this manual for more information. See the EEPROM (see Configuring Your EEPROM) of this manual for further details on how to change these EPROM values.


Shutdown Problems

Obviously if your halt script is not properly modified, apcupsd will not be able to shut off the power to the UPS, and if the power returns before the batteries are exhausted your system will not automatically reboot. In any case, your machine should have been cleanly shut down.


Master/Slave Shutdown

In master/slave configurations, however, the master cannot be 100 percent sure that the slaves have all shutdown before it performs the power off. As a consequence, it is possible that the master will shut off the power before the slave has finished shutdown. If this is the case, the best procedure is to put an appropriate sleep command in the /etc/apcupsd/apccontrol file on the master. For example to give the slaves 30 additional seconds to shutdown, one would add:

     sleep 30

just after the line that reads

     doshutdown)

in the apccontrol file (approximately line 79 - depending on your system version).

Also, on a slave machine, you do not want to use the modified halt script since it will recall apcupsd, which will detect that it is a slave (i.e. no connection to the UPS) and will complain that it cannot do the killpower. This situation is not harmful just annoying and possibly confusing.

One possible problem during shutdown can be caused by remnants of old versions. Please be sure to delete or rename all prior versions (/usr/local/sbin/apcupsd or /sbin/powersc).


Startup

Normally, apcupsd is automatically started when your system is rebooted. This normally occurs because the startup script apcupsd is linked into the appropriate places in /etc/rc.d. On most Linux systems, there is a program called chkconfig(8) that will automatically link the startup script. This program is invoked by the make install scripts, or it is explicitly done for those systems that do not have chkconfig(8). If this is not the case, you can either link it in appropriately yourself or explicitly call it from your rc.local file. The appropriate manual way to startup apcupsd is by executing:

     <path>/apcupsd start

where <path> is normally /etc/rc.d or /etc/rc.d/init.d depending on your system (isn't Unix wonderful? :-)). Using this script is important so that any files remaining around after a power failure are removed. Likewise, shutting down apcupsd should be done with the same script:

     <path>/apcupsd stop


Windows Considerations

Please see the end of Windows chapter (see Installation on Windows) of this manual for conderations pertaining to shutdown and killpower on Windows.


next up previous contents index
Next: APC smart protocol Up: Apcupsd User's Guide Previous: apcupsd Status Logging   Contents   Index
2009-11-06