Re: [Evolution] Evolution not listening to quit

[Patrick O'Callaghan <poc usb ve>]

On Tue, 2019-06-04 at 23:20 +0200, Ángel wrote:
> > In which case I think the argument about how to make sure Evo is
> > stopped before doing a backup is pointless. Just don't stop it.
> >
> > poc
>
> Even if a program is transactional, it only guarantees the state at a
> given point of time. Not that you can run a generic backup program in
> the background while the program works and that it will be consistent.
>
> In order to do that you would need to work on a frozen filesystem. For
> instance using LVM. btrfs also supports making a snapshot of a volume,
> which is atomic. Then you could run your backup program over that copy,
> and then (optionally) remove the snapshot.
>
> Suppose you were working locally on a maildir while you are running
> tar(1) for making a backup.¹
>
> 1- tar reads the list of files on cur/ and starts reading them one by
> one to store them
> 2- you read a message, it gets renamed from
> 1528146778.123_0.evolution:2, to 1528146778.123_0.evolution:2,S
> 3- tar attempts to backup ‘1559682696.123_0.evolution:2,’, but as it's
> not there, will log an error and continue.
>
> The file has been on your mailbox for a year. The rename itself is
> atomic. A power failure would not lose that file [if it's on a journaled
> fs]. Yet your backup missed it.

Good point, and another reason to use IMAP rather than POP. Even though
parts of the IMAP local state may be lost due to a race condition, it
can always be recovered from the server, which AFAIK *is*
transactional.

poc