On Wed, 2011-05-18 at 21:15 -0500, Robert Nichols wrote: > On 05/18/2011 06:42 PM, Simo Sorce wrote: > > On Wed, 2011-05-18 at 16:48 -0500, Robert Nichols wrote: > >> On 05/18/2011 04:04 PM, Lennart Poettering wrote: > >>> Host requests power down from UPS in 30s. Host then continues shut > >>> down. If the host now ends up taking more time then expected for > >>> shutting down it might still be busy at the time of the power going > >>> away. It's a race between "UPS powering off" and "system finishing > >>> shutdown". It's a bet that your system is faster than 30s when > >>> unmounting the remaining file systems, syncing the MD/DM metadata to > >>> disk, syncing ATA and so on (i.e. all the stuff the kernel does when you > >>> invoke the reboot() syscall). > >> > >> Here's another race. Host requests power down from UPS in 30s. Host > >> completes shutdown. At some point during that 30s interval, commercial > >> power is restored. Result: Host shuts down and never restarts. Sorry > >> about that. > >> > >> The way I've always prevented that is to have the host do a reboot, > >> not a shutdown, but send an immediate shutdown command to the UPS > >> just before sending control to the BIOS for the reboot. > > > > What you should do is to configure the BIOS to always boot on power-up. > > > > This way the UPS will remove power, figure out power is returned, > > reapply power and the BIOS will reboot the machine. > > Telling my UPS to turn off merely shuts down the inverter. If it is > not currently running on the inverter (because commercial power is > available), that is effectively a no-op, and power at the UPS output > remains on. Telling the BIOS to boot on power-up (which is how mine > is configured, BTW) does nothing since _power_never_went_away_. All > the BIOS sees is a command to shut down, which it does. And stays > that way. Absent manual intervention, the only thing that would bring > the system back up would be a power failure long enough to exceed the > capacity of the essentially unloaded UPS, and that would be _quite_ a > long time. IIRC some UPSs can be commanded to cycle power (ie interrupt all power to the machine) on shutdown anyway. Perhaps not all models do that. Simo. -- Simo Sorce * Red Hat, Inc * New York -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
