Hello,
I (think I) need to run two instances of Dovecot on one machine (rationale below, if someone's interested). They access the same mail share (NFS, maildir), but the indexes are kept on local storage. One of them would also provide lmtp service to local MTA.
For now I set the instances to keep indexes separate, in different directories, but I wonder, if they can share the indexes, to avoid unnecessary duplication? Of course, mmap_disable = yes, but would locking suffice? The platform is Linux (Devuan chimaera ATM, equivalet of Debian 11), filesystem - ext4, Dovecot version 2.3.13 (from distribution packages).
Why? I have to provide different authentication methods to external IMAP clients and locally-running webmail; at first I hoped to make it via remote filter, but docs state that “auth settings currently only support the protocol filter”, so I had to come with some other idea. It _is_ possible that users would be logged in both via external mail client and webmail at the same time – and even if not, there's also lmtp, that can run at any moment.
Sincerely, Bartosz Stępień