Sending email to root

It is pretty important that the root get asynchronous notification of problems detected by the maintenance system. However, it is obviously impossible to sent email in single-user mode (sendmail not running, boot drive write-protected). Therefore, there are two methods that could be used to notify root of errors or just of system status. The basic idea is that the message be written someplace other than the boot drive and then mailed in single-user mode via a launch daemon.

First, when a backup is done, it will be done to a writable medium, namely a firewire drive. This drive will be mounted when the system is running, so a message posted in /Volumes/Snapshots can easily be sent on to root. This will be the main method of notifying root about snapshots and clones.

Second, there are times when Snapshots isn't available. In fact, one of the critical messages might be that is wasn't available so no snapshot was made. In this case, the best method is to use /var/log/system.log. The system startup saves the standard output and standard error from rc.server (and other boot programs) in system.log. This is in fact a more reliable way to send notifications.

The approach will be simply to write out a banner lines like "org.bogs.rootmail begin" and "org.bogs.rootmail end" so that the daemon can simply extract the intermediate lines (if any) and mail them to root. In general, this should be limited to the bare minimum of lines. By default, system.log is cycled at midnight, and eight gzipped copies are kept around, which should be more than ample.

One thing this does is to complicate the daemon. Not only must it write out org.bogs.maintenance-mode, but it now has to send mail to root. This will require something to be run immediately after entering multi-user mode as well as something when it is time for more maintenance. Also, some kind of flag must be used to prevent multiple mailings, but I don't know what it should be. Maybe just a file ~root/.org.bogs.rootmail containing the timestamp of the last "org.bogs.rootmail end" line that was mailed out would be sufficient. That is, when the mailing script is run, it will send only more recent segments of system.log, and it will update the flag file.