try this.
FOR USB-FLASH CARD:
sudo backup –b –w –d usb-flash:// -n 1 –x xln
FOR FTP:
sudo backup –b –w –d ftp://login

assword@ip-address –x xln
Below is the Help Info:
dadmin@pbx> backup -h | more
Usage: backup [-b|-r] [-d destination] [-n #datasets] [-x]
[-t [dataset]] [-p pathname] [-k phrase] [-l] [-i file]
[-w] [--verbose][-?] -- dataset [dataset2 dataset3 ...]
-?: usage (this)
-b: backup
-r: restore
NOTE: The user should verify that the patch level
of the backup image is compatible with the
patch level of the machine that the backup
image is being restore to. To determine
the patch level of the backup image the
backup command with the -i option should
be issued.
-d: destination must be one of the following:
pccard://dirname (not supported on S8300)
usb-flash://dirname (not supported on S8300)
ftp://username

assword@hostname/dirname
mailto://username@domain/mailserver
/local_dir
-n: number of datasets to retain on pccard (for backup only)
-x: perform save translation prior to backup
-t: display the log for all backups
-t destination: display the backupsets located at destination
-t dataset: display the log for backups of a specific dataset
where dataset can be: xln, os, security, log
-p: specify the pathname where the files should be restored
-k: specify a pass phrase for encryption
-l: display the list of authorized datasets
-i: display information on the backup file
-fs: forces restore of backup image even if Definity image is
of a different version than that of the destination machine
-f: forces saving of translation files for translation set if
'-x' option is specified and the machine is active
--force_local: forces the use of local for backup destination if
specified for the backup of an 'upgrade' set
--verbose: long technical output
-- dataset: can be one or more of the following:
xln - Avaya Call Processing Translations
os - Server and System Files
security - Security Files
log - Log Files
NOTE: Listing of additional backupsets that may
be unique to your system configuration
can be obtained by specifying 'backup -l'.