question about fsck failing during startup

[Werner Schram]

scar wrote:
> hi, many thanks for your help.  but, a couple things...
>
> Werner Schram @ 12/09/2009 04:29 AM:
>   
>> You can check the status of your hard disk with palimpsets, which is 
>> available under System->administration->Disk Utility. 
>>     
>
> i can't find that. must not be installed. i checked add/remove programs
> and there is no 'disk utility'.  i also tried apt-get install
> palimpsets, but it cannot find the package.  is it available only for
> 9.10? (i am still on 9.04)
>   
Hey, you're right. I ran into this application on the mailing list, and 
thought: why havent I seen this application before? It didn't really 
occur to me that that was because it hasn't been available before :) And 
looking at Leonard's reply I could also have been clearer about the name 
of the application.

Right, an alternative is smartmontools (which is available in Jaunty). 
Its output a bit harder to read though. If you run the command you can 
see the current known status of the disk:

smartctl --all /dev/sda

To force a test (to update the current known status) you can use:

sudo smartctl --test=short /dev/sda
or
sudo smartctl --test=long /dev/sda

>> The fsck tool checks your filesystem consistency (do the files actually 
>> exists? Are the reported filesizes correct?), but with the -c option, it 
>> calls the badblocks tool to do a surface check on the entire partition 
>> (not the entire disk though) by trying to read every block and see if 
>> that works. You can do a read/write test with 'fsck -cc', altough I 
>> don't think that should be necessary.
>>     
>
> all right, so it sounds like fsck is just checking for data consistency.
>  then if it failed and there were read errors, then that means i am
> missing some data somewhere.  as i take daily backups of the system, is
> it possible to find out which data has become inaccessible and restore
> it? thanks
>   
If corrupted files have been detected, fsck should have notified you of 
that while or after the repairs. If it didn't you shouldn't worry about 
it much, your hard disk uses error detecting and correcting algorithms 
(see: 
http://en.wikipedia.org/wiki/Error_detection_and_correction#Data_storage) 
while storing data. So when errors are detected in time, they mostly can 
be corrected without damaging your data. You could check if you have a 
lost+found directory in the root of the mounted partition, and if that 
contains data. If fsck find files and doesn't know where they belong, it 
puts them there.

Werner