[Dovecot] Dsync error: Couldn't drop privileges: getgrnam

[Alan McGinlay - SICS]

Hi,

I upgraded (in place upgrade, preserving my dovecot configs) to a newer 
release of ubuntu in order to gain access to slightly newer Dovecot 
release and be able to use Dsync for migration from Cyrus, here is my 
doveconf -n output:

# 2.1.7: /etc/dovecot/dovecot.conf
# OS: Linux 3.5.0-44-generic x86_64 Ubuntu 12.10
auth_debug = yes
auth_default_realm = whatever.com
auth_master_user_separator = *
auth_socket_path = /var/run/dovecot/auth-master
imapc_features = rfc822.size
imapc_host = oldmail.whatever.com
imapc_master_user = cyradmin
imapc_password = <password hidden>
mail_chroot = /var/vmail
mail_debug = yes
mail_gid = 5000
mail_location = maildir:~/Maildir
mail_prefetch_count = 20
mail_privileged_group = vmail
mail_uid = 5000
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope 
encoded-character vacation subaddress comparator-i;ascii-numeric 
relational regex imap4flags copy include variables body enotify 
environment mailbox date ihave
passdb {
   args = /etc/dovecot/master-users
   driver = passwd-file
   master = yes
}
passdb {
   args = /etc/dovecot/dovecot-ldap.conf.ext
   driver = ldap
}
plugin {
   sieve = ~/.dovecot.sieve
   sieve_dir = ~/sieve
}
protocols = " imap lmtp sieve pop3"
service auth-worker {
   user = $default_internal_user
}
service auth {
   unix_listener /var/spool/postfix/private/auth {
     mode = 0666
   }
   unix_listener auth-userdb {
     group = dovecot
     mode = 0600
     user = dovecot
   }
}
service lmtp {
   unix_listener /var/spool/postfix/private/dovecot-lmtp {
     group = postfix
     mode = 0600
     user = postfix
   }
}
service managesieve-login {
   inet_listener sieve {
     port = 4190
   }
}
ssl_cert = <cert
ssl_key = <cert
userdb {
   args = uid=vmail gid=vmail home=/domain/%1d/%d/%1n/%n 
allow_all_users=yes
   driver = static
}
protocol lmtp {
   postmaster_address = post at whatever.com
}
protocol imap {
   mail_max_userip_connections = 10
}
protocol pop3 {
   pop3_uidl_format = %v.%u
}

And the command I am using to (attempt) a mailbox sync:

doveadm -o mail_fsync=never backup -R -u alantestuser at whatever.com 
imapc:

Produces this output:

dsync(alantestuser at whatever.com): Error: user 
alantestuser at whatever.com: Couldn't drop privileges: getgrnam(vmail) 
failed: No such file or directory (in mail_privileged_group setting)
dsync(alantestuser at whatever.com): Fatal: User init failed

mail.log shows this:

Dec  5 21:10:54 newmailserver dovecot: auth: Debug: Loading modules 
from directory: /usr/lib/dovecot/modules/auth
Dec  5 21:10:54 newmailserver dovecot: auth: Debug: Loading modules 
from directory: /usr/lib/dovecot/modules/auth
Dec  5 21:10:54 newmailserver dovecot: auth: Debug: Module loaded: 
/usr/lib/dovecot/modules/auth/libauthdb_ldap.so
Dec  5 21:10:54 newmailserver dovecot: auth: Debug: passwd-file 
/etc/dovecot/master-users: Read 1 users in 0 secs
Dec  5 21:10:54 newmailserver dovecot: auth: Debug: master in: 
USER#0111#011alantestuser at whatever.com#011service=doveadm
Dec  5 21:10:54 newmailserver dovecot: auth: Debug: master out: 
USER#0111#011alantestuser at whatever.com#011uid=5000#011gid=5000#011home=/domain/w/whatever.com/a/alantestuser

I followed this doc (which could use a little fleshing out, I will be 
happy to do it once I get a grasp on this!): 
http://wiki2.dovecot.org/Migration/Dsync

Thanks in advance!

/Alan