Run script before and after backup to mount temporary disk

Several of our site backups fail since there isn't enough diskspace on the local disk for the zipfile to be created before beeing copied to external storage.

If there was a possibility to run a script before and after the backup starts I can mount a temporary disk and create the zipfile on that. The temporary disk are then unmounted again after the backup.

Example

mount temporary disk
create zipfile on temporary disk
upload zipfile to external storage
delete zipfile from temporary disk
unmount temporary disk