Trying to take a full backup before doing a update. (Zimbra NE Pro)

The Admin UI says i have to take a zmbackup -f as zimbra user, but this give me:

[zimbra@epost root]$ zmbackup -f
Error parsing command line arguments: Account email addresses are required
usage: zmbackup {-f | -i | -del} <options>
-a,--account <arg> Account email addresses seperated by white space
or "all" for backing up all accounts. Required.
-d,--debug Display diagnostics for debugging purposes.
-del,--delete <arg> Deletes backups including and prior to the
specified label, date (YYYY/MM/DD[-hh:mm:ss]) or period (nn{d|m|y}).
-f,--fullBackup Starts full backup.
-h,--help Displays this help message.
-i,--incrementalBackup Starts incremental backup.
-s,--server <arg> Mail server hostname. Default is localhost.
-sync,--sync Runs full backup synchronously.
-t,--target <arg> Backup target location (default
<zimbra_home>/backup).
-z,--zip Zips email blobs in backup.

Exactly one of -f, -i, or -del must be specified.

also tried with zmbackup -f all