To install smartctl (and smartd with it):
sudo apt-get install smartmontools
Why would you want SmartMonTools?
The smartmontools package contains two utility programs (smartctl and smartd) to control and monitor storage systems using the Self-Monitoring, Analysis and Reporting Technology System (S.M.A.R.T.) built into most modern ATA and SCSI hard disks. It is derived from the smartsuite package, and includes support for ATA/ATAPI-5 disks. It should run on any modern Linux system.
Very handy; especially as the OS drive just died in the RAID5 box 🙁 I’m now taking extra precautions!