Re: [systemd-devel] Trying to turn off a UPS with home-made service unit
On Wed Sep 11 10:45:48 PDT 2013 Lennart Poettering wrote: So, it's a really bad idea to turn off UPS from userspace, simply because you will race against the kernel's fs sync() code, and you never know what will finish first: your UPS shutdown timeout or your fs sync(). Doing this from userspace is hence racy. If you want to use a hack like this then at least do it via the /usr/lib/systemd/system-shutdown/ drop-in directory which is called very late during shutdown. It will shorten the race window, but not erase it, since the kernel will flush various buffers only after the reboot() system call is invoked. 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 | || 0 2 | 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 secs | | upsdrvctl UPS shutdownshutdown 2) Replaced by script in /usr/lib/systemd/system-shutdown/ systemctl system poweroff halt | || 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 #! /bin/bash # Delayed turn off for the UPS unit. # Needed for automatic system restart when wall power returns. UPSDRVCTL_BIN=/usr/lib/ups/driver/upsdrvctl $UPSDRVCTL_BIN shutdown I tried adding echo `date -I` `date +%T` "$0 calls $UPSDRVCTL_BIN shutdown" >> /var/log/UPS.log to get a trace of the activity, but nothing is written in /var/log/UPS.log. Roger ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] Trying to turn off a UPS with home-made service unit
On Sat, 10.08.13 17:02, Roger Price (ro...@rogerprice.org) wrote: > I am new to systemd and I am trying to power off a UPS unit using a > home-made service unit > /lib/systemd/system/ups-delayed-shutdown.service running on openSUSE > 12.3. So, it's a really bad idea to turn off UPS from userspace, simply because you will race against the kernel's fs sync() code, and you never know what will finish first: your UPS shutdown timeout or your fs sync(). Doing this from userspace is hence racy. If you want to use a hack like this then at least do it via the /usr/lib/systemd/system-shutdown/ drop-in directory which is called very late during shutdown. It will shorten the race window, but not erase it, since the kernel will flush various buffers only after the reboot() system call is invoked. See systemd-shutdown(8) for details. Lennart -- Lennart Poettering - Red Hat, Inc. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] Trying to turn off a UPS with home-made service unit
On Sat, 10 Aug 2013, Andrey Borzenkov wrote: Home made service should normally go into /etc/systemd. I moved my service to /etc/systemd/system/ [Unit] You need to add DefaultDependencies=no. Otherwise your service will conflict with shutdown.target. I added DefaultDependencies=no and my service works! systemd --system --test --unit poweroff.target --log-level debug can be used to see what would be started and why. Thanks for your help! Roger ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
