I used this script for years on my VPS. And it\'s still working.
DBLIST=`mysql -uroot -pROOT_PASSWORD -ANe\"SELECT GROUP_CONCAT(schema_name) FROM information
Faced with the same problem. I do not know why exactly, but if you add the utility PV concluded that all works. Maybe it depends on your shell bash/sh.
sudo apt-get install pv
PipeViewer it a very usefull utility, it allows you to visualize processes of writing to disk, for example.
Script for example
mysqldump ${MYSQLDUMP_OPTIONS} ${DB} | gzip | pv > ${BACKUP_DEST}/${DB}.sql.gz