Error using dsync to convert really old mboxes to Maildir and workaround

[faginbagin]

On 9/24/2018 1:50 AM, faginbagin wrote:
> I ran across what I think may be a bug in dsync when trying to convert from mbox to Maildir format. My first attempt failed with a runaway dsync process spewing out thousands of identical lines of the form:
> 
> dsync(buus): Error: Duplicate mailbox GUID 00fe691ff60da85b090d0000c8119523 for mailboxes Archive/Personal and Work/VendorInfo - giving a new GUID 00fe691ff60da85b090d0000c8119523 to Archive/Personal
> 
> These two mail folders happen to be among a number of folders I've had for many years, but also haven't looked at in many years. I used to use UW-IMAP, but switched to dovecot about two years ago, and I'm sure I've never used dovecot to look at those folders. So I suspect the root cause of the above error message was that dovecot had never generated GUIDs for these and some other really old folders.
> 
> After killing dsync with SIGKILL, which couldn't be killed with SIGTERM, I restored my mbox format Mail folder from backup, restored the mail_location and then coerced dovecot to generate unique GUIDs for all my mail folders with this command:
> 
> doveadm mailbox status guid `doveadm mailbox list`
> 
> After the above command, I was able to convert my mail from mbox to Maildir format.
> 
> Maybe this will help someone else somewhere down the road.

Forgot to provide dovecot -n output:

# 2.2.27 (c0f36b0): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.4.16 (fed8554)
# OS: Linux 4.9.0-8-686-pae i686 Debian 9.5
mail_location = maildir:~/Maildir
# mail_location was the following when error occurred:
# mail_location = mbox:~/Mail:INBOX=/var/mail/%u:UTF-8
# Also separator was not set when error occurred.
mail_privileged_group = mail
namespace inbox {
  inbox = yes
  location =
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix =
  separator = /
}
passdb {
  driver = pam
}
protocols = " imap"
ssl_cert = </etc/dovecot/dovecot.pem
ssl_key =  # hidden, use -P to show it
userdb {
  driver = passwd
}