Re: [rdiff-backup-users] Feature suggestion: Ability to keep a certain number of snapshots

[Charles Duffy]

Peter Schuller wrote:
> Hello,
>
> I am always reluctant to use --remove-older-than in scripts because
> there is always the possibility that the clock is screwed up for
> whatever reason and it decides to remove all reverse diffs. Often I
> would find it very useful to be able to say "keep the N newest
> snapshots and remove the rest", which is safer.
>
> In addition, it tends to give a pretty natural balance between
> frequently changing backup targets and targets that seldom changes. If
> a target changes relatively seldom (e.g., /etc) one might be more
> inclined to want to keep 30 snapshots instead of 30 days (the latter
> of which might translate into just the latest mirror).
>
> Thoughts?
>   
I would find this extremely useful myself -- though it can be simulated 
by getting a list of increments, backtracking through it to find the 
30th (should it exist), and then calling remove-older-than with that 
date. Much easier to have a remove-more-than option, though, I agree.

Do you think it would make sense to define behaviour for when both 
remove-more-than and remove-older-than are used? It otherwise would be 
ambiguous as to whether such indicates one wishes to remove anything 
that matches *both* criteria, or anything that matches *either* 
criteria. Personally, I think the former is more useful -- removing 
anything that matches *either* could be done with two separate runs, 
whereas removing anything that matches *both* couldn't.