Comment 16 for bug 412470

I think we have to be clear what BackInTime should be able to do and which kind of program it is..

It's nice that BiT can be run by any user, but as root you have more possibilities: you could use anacron or backup the whole system. Maybe this can be detected and BiT could behave different?

Should BiT support FAT32 and be (quite) efficient on it? This would mean to have only folders in the snapshot directory, which are rsynced. But in the GUI, it's nice to see each snapshot as a full folder set, even if only one of them was rsynced. I mean a good example is: backup (almost) the whole system monthly, but a specified folder like /home/peter/documents every hour.

On FAT32, this takes a lot of space which is wasted absolutely senseless. On ext3/ext4, hardlinking solves this problem, but is still an overhead when it comes to a lot of files.

If you say goodbye to the a-snapshot-has-all-files approach, an hourly snapshot would contain only /home/peter/documents, the monthly all files and the "latest_snapshot" also (like I wrote under answers). But of course it can get much less convenient to look for a specific file, or a extra logic is needed to support the user. Actually, this extra logic could be a soft link! I will explain my idea:

There are more than one folder configured and they have different frequencies. Let's say "/" monthly and "/home/peter/documents" hourly.

In the backintime directory, there is a folder "latest_snapshot" which has always the latest status of files which got rsync'ed. Also there are the snapshots like 20090831-204000 or so. A cronjob will do like this:

If it's the monthly run, rsync including both folders mentioned using root and the "latest_snapshot". Then copy (cp -al) it to the snapshot (with the date in the name).

If it's the hourly run, rsync only including the "/home/peter/documents", also using "latest_snapshot". Then copy (cp -al) _this_ folder to the named snapshot.

It knows, which snapshot was with the next-lower frequency (here monthly) and does soft-links of the ignored folders into the current snapshot. Softlinks have a big disadvantage: we have to be carefull with removing snapshots! If we don't do the links, the new snapshot only contains 'documents', which is ok for me and saves space on FAT32.

About the problem of non-disjoint folders: If the subfolder has a lower frequency, it can be excluded with "--exclude" and won't be rsynced. Don't do the softlinks in that case. If the subfolder has higher frequency, this shouldn't be a problem, as only the subfolder got rsynced and copied into the new snapshot.