====== rsnapshot-backup / development ======

===== error handling =====

==== STDOUT ====

The messages which are printed to stdout by rsync 
are directed to a log file by rsnapshot.

The name of the log file follows the entry ''logfile''
in the config file for the backup job.

It defaults to ''/var/log/rsnapshot-backup/<systemname>/log'' which is renamed to 
''/var/log/rsnapshot-backup/<systemname>/log-<YYYYmmdd-HHMMSS>'' after the backup 
job is completed.

==== STDERR ====

Unfortunately, rsnapshot lets escape rsync's stderr messages
without recording them. So they would end up on your terminal or 
most likely are cought by cron and sent per email.

Rsnapshot-backup intercepts rsnapshot's stderr and redirects the message to 
a file which name is derived from the ''logfile'' entry 
in the config file for the backup job.

It defaults to ''/var/log/rsnapshot-backup/<systemname>/log-error'' which is renamed to 
''/var/log/rsnapshot-backup/<systemname>/log-error-<YYYYmmdd-HHMMSS>'' after the backup 
job is completed.

The ''-error'' part of the file name is not configurable.

If there is no output on stderr there will be no ''log-error-*'' file.

The time stamps in the file names are identical for ''log-*'' and ''log-error-*'' so
the two corresponding log files can be matched easily.

===== how to provoke an error for testing =====

<code>
mkdir /root/tmp
cd    /root/tmp
while sleep 0.05 ; do  ( F=$( mktemp xxx-$( date -Is )-XXXXXX ) ; date > $F; sleep 0.2 ; rm $F ) & done
</code>

This creates 20 files per second which are removed after 200ms.

The error provoked would be something like:

<code>
------ BACKUP OF '/etc/rsnapshot-backup.d/enabled/conf.vstest01' ------
file has vanished: "/root/tmp/xxx-2017-06-27T14:13:50+0000-STgDmA"
rsync warning: some files vanished before they could be transferred (code 24) at main.c(1655) [generator=3.1.1]
----------------------------
</code>