4 Power management

Unfortunately, this is not very reliably supported under FreeBSD. If you are lucky, some functions may work reliably; or they may not work at all.

To enable this, you may need to compile a kernel with power management support (device apm0) or add the option enable apm0 to /boot/loader.conf, and also enable the apm daemon at boot time (line apm_enable="YES" in /etc/rc.conf). The apm commands are listed in the apm(8) manpage. For instance, apm -b gives you battery status (or 255 if not supported), apm -Z puts the laptop on standby, apm -z (or zzz) suspends it. To shutdown and power off the machine, use shutdown -p. Again, some or all of these functions may not work very well or at all. You may find that laptop suspension/standby works in console mode but not under X (that is, the screen does not come on again; in that case, switch to a virtual console (using Ctrl-Alt-F1 or another function key) and then execute the apm command.

The X window system (XFree86) also includes display power management (look at the xset(1) manual page, and search for ``dpms'' there). You may want to investigate this. However, this, too, works inconsistently on laptops: it often turns off the display but does not turn off the backlight.