How to check hard disk health in linux step by step

First check for I/O errors in /var/log/messages  if you found any error then there is something wrong with hard disk.

There is SMART utility for monitoring hard disks

SMART stands for Self-Monitoring, Analysis, and Reporting Technology

for using this SMART utilities first we should make sure that feature is enabled  in BIOS

 there are some tools that need to be installed for using this feature

to check weather SMART tools are installed and SMART commands work use this command

smartctl -i /dev/sda1 or sda2 etc...

In ubuntu we can install tools by

sudo apt-get install smartmontools

for checking health use

smartctl -a /dev/hda

example output

-------------------------------------------------------------------------------------

smartctl version 5.37 [i686-pc-linux-gnu] Copyright (C) 2002-6 Bruce Allen
Home page is http://smartmontools.sourceforge.net/

=== START OF INFORMATION SECTION ===
Model Family:     Western Digital Caviar SE family
Device Model:     WDC WD3200JB-00KFA0
Serial Number:    WD-WCAMR2493175
Firmware Version: 08.05J08
User Capacity:    320,072,933,376 bytes
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   6
ATA Standard is:  Exact ATA specification draft version not indicated
Local Time is:    Sat Apr 17 12:39:35 2010 CDT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

General SMART Values:
Offline data collection status:  (0x84) Offline data collection activity
                                        was suspended by an interrupting command                              from host.
                                        Auto Offline Data Collection: Enabled.
Self-test execution status:      (   0) The previous self-test routine completed
                                        without error or no self-test has ever
                                        been run.
Total time to complete Offline
data collection:                 (9600) seconds.
Offline data collection
capabilities:                    (0x7b) SMART execute Offline immediate.
                                        Auto Offline data collection on/off supp                             ort.
                                        Suspend Offline collection upon new
                                        command.
                                        Offline surface scan supported.
                                        Self-test supported.
                                        Conveyance Self-test supported.
                                        Selective Self-test supported.
SMART capabilities:            (0x0003) Saves SMART data before entering
                                        power-saving mode.
                                        Supports SMART auto save timer.
Error logging capability:        (0x01) Error logging supported.
                                        No General Purpose Logging support.
Short self-test routine
recommended polling time:        (   2) minutes.
Extended self-test routine
recommended polling time:        ( 116) minutes.
Conveyance self-test routine
recommended polling time:        (   6) minutes.

SMART Attributes Data Structure revision number: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_                             FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x000f   200   200   051    Pre-fail  Always       -                                    0
  3 Spin_Up_Time            0x0003   247   188   021    Pre-fail  Always       -                                    2633
  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -                                    949
  5 Reallocated_Sector_Ct   0x0033   186   186   140    Pre-fail  Always       -                                    105
  7 Seek_Error_Rate         0x000f   200   200   051    Pre-fail  Always       -                                    0
  9 Power_On_Hours          0x0032   074   074   000    Old_age   Always       -                                    19124
 10 Spin_Retry_Count        0x0013   100   100   051    Pre-fail  Always       -                                    0
 11 Calibration_Retry_Count 0x0012   100   100   051    Old_age   Always       -                                    0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -                                    876
194 Temperature_Celsius     0x0022   116   103   000    Old_age   Always       -                                    34
196 Reallocated_Event_Count 0x0032   180   180   000    Old_age   Always       -                                    20
197 Current_Pending_Sector  0x0012   200   200   000    Old_age   Always       -                                    0
198 Offline_Uncorrectable   0x0010   200   200   000    Old_age   Offline      -                                    0
199 UDMA_CRC_Error_Count    0x003e   200   200   000    Old_age   Always       -                                    0
200 Multi_Zone_Error_Rate   0x0009   200   200   051    Pre-fail  Offline      -                                    0

SMART Error Log Version: 1
No Errors Logged

SMART Self-test log structure revision number 1
No self-tests have been logged.  [To run self-tests, use: smartctl -t]


SMART Selective self-test log data structure revision number 1
 SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS
    1        0        0  Not_testing
    2        0        0  Not_testing
    3        0        0  Not_testing
    4        0        0  Not_testing
    5        0        0  Not_testing
Selective self-test flags (0x0):
  After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute delay.

--------------------------------------------------------------------------------------------------------------------------------

smartctl -d ata -a /dev/sda

or

smartctl -d ata -H /dev/sdb

smartctl -t long /dev/sda

example output

-----------------
smartctl version 5.37 [i686-pc-linux-gnu] Copyright (C) 2002-6 Bruce Allen
Home page is http://smartmontools.sourceforge.net/

=== START OF OFFLINE IMMEDIATE AND SELF-TEST SECTION ===
Sending command: "Execute SMART Extended self-test routine immediately in off-line mode".
Drive command "Execute SMART Extended self-test routine immediately in off-line mode" successful.
Testing has begun.
Please wait 116 minutes for test to complete.
Test will complete after Sat Apr 17 14:49:23 2010


Once the test is completed we can see the output by

sudo smartctl -d ata --attributes --log=selftest /dev/sda