On 09/15/2013 04:30 PM, Roger Price wrote:
Here is the effect on a simple openSUSE 12.3 test rig of replacing my home-made service unit /lib/systemd/system/ups-delayed-shutdown.service with a script in the /usr/lib/systemd/system-shutdown/ drop-in directory. I used the default UPS offdelay of 20 secs. The X's indicate the race window. (Sorry for the ascii art.)1) My "bad idea" ups-delayed-shutdown.service systemctl system poweroff halt | |XXXXXXXXXXXXXXXX| 0 2 | 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 secs | | upsdrvctl UPS shutdown shutdown 2) Replaced by script in /usr/lib/systemd/system-shutdown/ systemctl system poweroff halt | |XXXX| 0 2 4 6 8 |10 12 14 16 18 20 22 24 26 28 30 32 secs | | upsdrvctl UPS shutdown shutdown The script solution has the advantage of reducing the race window from 9 to 3 secs. Note that the same security can also be achieved by the service unit by setting offdelay = 26 in ups.conf. My script is
you are wrong. The catch is that in the first case, time between "upsdrvctl shutdown" and "system halt" is varying. Only in your case it's 9 seconds. With network mounted disks it can take 100 seconds or more without any problem. On the other hand, in the second case 1)there is no task that can take a lot more time than usual, 2)nothing really important happens here, so even if you turn power off here, you can have disk that does not have parked heads, but that's no biggie and no data loss.
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