How to pause shutdown?

[Henning Moll]

Hi,

i have a direct question to upstart, but please let me first give you some background information: 

on my ubuntu desktop i implemented a system to automatically backup my system on a daily basis via rsnapshot. The backup is started by anacron. While the backup is running, a lockfile is present. 

To avoid broken backups i tried to pause a user intended shutdown as long as the lockfile exists. Up to now i was able to achieve this by introducing some runlevel scripts (rc1.d/K12backup_wait and rc0.d/K12backup_wait). The script behind these links just waits until the lockfile is no longer valid. After this, the shutdown continued just as normal.

Now that Ubuntu is using upstream more and more, i am not able to this the same way (i recently installed 10.10).

Now my question: Is it possible to implement this with upstart? How?
For my backup solution it is also neccessary that network (cable lan) and sshd stays intact.

Best regards
Henning

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