On 10/06/2011 05:01 PM, Michael Schwendt wrote: >>> you would not notice any troubles. >> >> Umm, yes you would. That's not atomic, and risks leaving things in an >> inconsistent state. >> >> http://www.flamingspork.com/talks/2007/06/eat_my_data.odp >> http://www.pixelbeat.org/docs/unix_file_replacement.html > > cp -f ${grub_cfg}.new ${grub_cfg} ; rm -f ${grub_cfg}.new > > Better? No. cp is not atomic. rename(2) (via mv(1), if both files are on the same device) is. Any solution that does not use rename(2) is flawed, because an ill-timed power-outage will leave the file in an inconsistent state. What you want is that ${grub_cfg} _always_ exists, and is either the unchanged original, or atomically the contents of the new replacement. Anything else is a recipe for disaster, for something as important as the files that control how you boot your machine. > I assume you are not concerned about the removal of the temporary > local file in the second step, Not as much as I am that ${grub_cfg} always exist, and always have valid contents. -- Eric Blake eblake@xxxxxxxxxx +1-801-349-2682 Libvirt virtualization library http://libvirt.org -- test mailing list test@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe: https://admin.fedoraproject.org/mailman/listinfo/test
