I tried this command also. It didn't work. It shows syntax again. Please see the supported commands in dovecot 2.0.9 version. This doesn't support replication also as per syntax, if i am not wrong. Please suggest me.
[root@production ~]# doveadm backup -u
kishore@test.org.com remote:vmail@production2.test.org.comusage: doveadm [-Dv] [-f <formatter>] <command> [<args>]
altmove [-u <user>|-A] [-S <socket_path>] <search query>
auth [-a <auth socket path>] [-x <auth info>] <user> [<password>]
config [doveconf parameters]
director add|flush|map|remove|status
dump [-t <type>] <path>
expunge [-u <user>|-A] [-S <socket_path>] <search query>
fetch [-u <user>|-A] [-S <socket_path>] <fields> <search query>
force-resync [-u <user>|-A] [-S <socket_path>] <mailbox>
help <cmd>
import [-u <user>|-A] [-S <socket_path>] <source mail location> <dest parent mailbox> <search query>
kick [-a <anvil socket path>] [-f] <user mask>[|]<ip/bits>
log find|reopen|test
mailbox create|delete|list|mutf7|rename|status|subscribe|unsubscribe
penalty [-a <anvil socket path>] [<ip/bits>]
purge [-u <user>|-A] [-S <socket_path>]
pw [-l] [-p plaintext] [-r rounds] [-s scheme] [-u user] [-V]
reload
search [-u <user>|-A] [-S <socket_path>] <search query>
sis deduplicate|find
stop
user [-a <userdb socket path>] [-x <auth info>] <user mask> [...]
who [-a <anvil socket path>] [-1] [<user mask>] [<ip/bits>]