thanks for taking the time to answer. Unfortunately, I get the same error with the right command (without the -1)
 
infoomatic
 
 
Gesendet: Donnerstag, 12. Juli 2018 um 19:57 Uhr
Von: "Sami Ketola" <sami.ketola@dovecot.fi>
An: dovecot <dovecot@dovecot.org>
Cc: Infoomatic <infoomatic@gmx.at>
Betreff: Re: dsync panic
 
 
On 7 Jul 2018, at 4.31, Infoomatic <infoomatic@gmx.at> wrote:
 
Hi,
I just upgraded from dovecot 2.2.19 to 2.3.2. "doveadm backup" worked fine in v 2.2.19, but now panics (user with shared folder):
/opt/dovecot/bin/doveadm backup -u testuser -1 sdbox:/tmp/testuser
 
Not sure why it panics, but at least your command line looks incorrect. 
 
please try: doveadm backup -u testuser sdbox:/tmp/testuser
 
your options are:
 
doveadm backup
doveadm sync
doveadm sync -1
 
 
Sami