Linux: Finding the serial number of a hard drive

Finding the serial number of a hard drive on a Linux console (as root) is simple with the right tool.
The right tool in this case is hdparm (using the -i option).
-i will query the device directly for the details.


themachine:/proc# hdparm -i /dev/sda
 Model=ST31500341AS                            , FwRev=CC1H    , SerialNo=            9VS21ZXM
 Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs RotSpdTol>.5% }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4
 BuffType=unknown, BuffSize=0kB, MaxMultSect=16, MultSect=?16?
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=18446744072344861488
 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes:  pio0 pio1 pio2 pio3 pio4 
 DMA modes:  mdma0 mdma1 mdma2 
 UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6 
 AdvancedPM=no WriteCache=enabled
 Drive conforms to: unknown:  ATA/ATAPI-4,5,6,7
 * signifies the current active mode

Using the option -I instead gives even more information:

themachine:/proc# hdparm -I /dev/sda
ATA device, with non-removable media
        Model Number:       ST31500341AS                            
        Serial Number:      9VS21ZXM
        Firmware Revision:  CC1H    
        Transport:          Serial
        Used: unknown (minor revision code 0x0029) 
        Supported: 8 7 6 5 
        Likely used: 8
        Logical         max     current
        cylinders       16383   16383
        heads           16      16
        sectors/track   63      63
        CHS current addressable sectors:   16514064
        LBA    user addressable sectors:  268435455
        LBA48  user addressable sectors: 2930277168
        device size with M = 1024*1024:     1430799 MBytes
        device size with M = 1000*1000:     1500301 MBytes (1500 GB)
        LBA, IORDY(can be disabled)
        Queue depth: 32
        Standby timer values: spec'd by Standard, no device specific minimum
        R/W multiple sector transfer: Max = 16  Current = ?
        Recommended acoustic management value: 254, current value: 0
        DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 udma5 *udma6 
             Cycle time: min=120ns recommended=120ns
        PIO: pio0 pio1 pio2 pio3 pio4 
             Cycle time: no flow control=120ns  IORDY flow control=120ns
        Enabled Supported:
           *    SMART feature set
                Security Mode feature set
           *    Power Management feature set
           *    Write cache
           *    Look-ahead
           *    Host Protected Area feature set
           *    WRITE_BUFFER command
           *    READ_BUFFER command
           *    DOWNLOAD_MICROCODE
                SET_MAX security extension
           *    Automatic Acoustic Management feature set
           *    48-bit Address feature set
           *    Device Configuration Overlay feature set
           *    Mandatory FLUSH_CACHE
           *    FLUSH_CACHE_EXT
           *    SMART error logging
           *    SMART self-test
           *    General Purpose Logging feature set
           *    WRITE_{DMA|MULTIPLE}_FUA_EXT
           *    64-bit World wide name
                Write-Read-Verify feature set
           *    WRITE_UNCORRECTABLE_EXT command
           *    {READ,WRITE}_DMA_EXT_GPL commands
           *    Segmented DOWNLOAD_MICROCODE
           *    SATA-I signaling speed (1.5Gb/s)
           *    SATA-II signaling speed (3.0Gb/s)
           *    Native Command Queueing (NCQ)
           *    Phy event counters
                Device-initiated interface power management
           *    Software settings preservation
           *    SMART Command Transport (SCT) feature set
           *    SCT Long Sector Access (AC1)
           *    SCT LBA Segment Access (AC2)
           *    SCT Error Recovery Control (AC3)
           *    SCT Features Control (AC4)
           *    SCT Data Tables (AC5)
                unknown 206[12] (vendor specific)
        Master password revision code = 65534
        not     enabled
        not     locked
        not     frozen
        not     expired: security count
                supported: enhanced erase
Logical Unit WWN Device Identifier: 5000c50014ec1f60
        NAA             : 5
        IEEE OUI        : c50
        Unique ID       : 014ec1f60
Checksum: correct