[CentOS] Disappearing directory

Hi All and happy new year,

Via a cron job a USB disk is mounted on a Centos 6.4 machine for backup and dismounted after. I've noticed this failing. See below, the backup directory that was in /mnt had disappeared, so creating it again as follows...

# cd /mnt # mkdir backup # mount /dev/sdb1 /mnt/backup/ # ls backup # cd backup/ # ls boot.tar.gz etc etc.tar.gz home home.tar.gz ident.txt lost+found named.tar.gz root.tar.gz usr.tar.gz var var.tar.gz # cd .. # ls backup # umount /dev/sdb1 # ls

# cat /etc/redhat-release CentOS release 6.4 (Final)

After the umount the directory vanishes. What gives or have I lost the plot in 2014. (This works as I'd expect on an old fc14 system I have)

:-) Ken