No incremental backup per cron schedule after specifying alternate backup location

Hi,

On my network edition, Release 6.0.4_GA_2038.UBUNTU8 UBUNTU8 NETWORK, I changed the default backup location using: -

zmprov mcf zimbraBackupTarget /alternate/directory/

This is the section from the crontab relevant to backup: -

0 1 * * 6 /opt/zimbra/bin/zmbackup -f -a all --mail-report
0 1 * * 0-5 /opt/zimbra/bin/zmbackup -i --mail-report
0 0 * * * /opt/zimbra/bin/zmbackup -del 1m --mail-report

The system created a full backup in the /alternate/directory the first night. But has not created any backups subsequently.

I am ok with the default backup schedule (as shown above). I just need to have the system take backups in my /alternate/directory per the above schedule.

Any pointers greatly appreciated.

Thanks!