Re: Possible bug in mkfs.ext3

jd1008 <[email protected]> Sat, 20 Sep 2014 12:38:18 -0600
Newsgroups gmane.comp.file-systems.ext3.user
Message-ID <[email protected]>
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The -S was advised by a member of the Fedora Users Mailing List,
and I thought I would try it.
I still have the original disk, so no permanent harm.
I keep trying what is suggested on a copy of the partition.

Only drag is the copying :)
It is a 400GiB partition (400 * 1024^3).

I am currently scanning the parition for a superblock, starting at -b 0,
and keep incrementing by 512, until I find what"might be" a superblock;
i.e. fsck does not say "Bad magic number". Of course, that's no guarantee
it is a superblock, but it gives me an opportunity to examine the superblock
at that offset.

Regards,

JD


On 09/20/2014 12:14 PM, Theodore Ts'o wrote:
> On Fri, Sep 19, 2014 at 07:56:37PM -0600, jd1008 wrote:
>> I am reporting this on the advice of the Fedora Users Mailing List Member.
>>
>> This the mailing list exchange outlining the problem with specifying -S to
>> mkfs,
>> and it's subsequent consequences when fsck is run.
> If none of the possible superblocks are valid when using mke2fs -b
> <NNN>, there's a good chance that your partition table (or LVM
> metadata) has gotten corrupted.  You should definitely check to make
> sure the partition setup is sane before trying to use mke2fs -S.
>
> It's also true, as Andreas has stated, that with the large number of
> new file system options and layouts with ext4, mke2fs -S is much more
> hazardous unless you __really__ know what you are doing.  It would
> probably be a good idea to have some warning messages to that effect
> in the man page.
>
> 						- Ted
>


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    <font size="+1"><font face="Times New Roman, Times, serif">The -S
        was advised by a member of the Fedora Users Mailing List,<br>
        and I thought I would try it.<br>
        I still have the original disk, so no permanent harm.<br>
        I keep trying what is suggested on a copy of the partition.<br>
        <br>
        Only drag is the copying :)<br>
        It is a 400GiB partition (400 * 1024^3).<br>
        <br>
        I am currently scanning the parition for a superblock, starting
        at -b 0,<br>
        and keep incrementing by 512, until I find what"might be" a
        superblock;<br>
        i.e. fsck does not say "Bad magic number". Of course, that's no
        guarantee<br>
        it is a superblock, but it gives me an opportunity to examine
        the superblock<br>
        at that offset.<br>
        <br>
        Regards,<br>
        <br>
        JD<br>
        <br>
        <br>
      </font></font>
    <div class="moz-cite-prefix">On 09/20/2014 12:14 PM, Theodore Ts'o
      wrote:<br>
    </div>
    <blockquote cite="mid:[email protected]" type="cite">
      <pre wrap="">On Fri, Sep 19, 2014 at 07:56:37PM -0600, jd1008 wrote:
</pre>
      <blockquote type="cite">
        <pre wrap="">I am reporting this on the advice of the Fedora Users Mailing List Member.

This the mailing list exchange outlining the problem with specifying -S to
mkfs,
and it's subsequent consequences when fsck is run.
</pre>
      </blockquote>
      <pre wrap="">
If none of the possible superblocks are valid when using mke2fs -b
&lt;NNN&gt;, there's a good chance that your partition table (or LVM
metadata) has gotten corrupted.  You should definitely check to make
sure the partition setup is sane before trying to use mke2fs -S.

It's also true, as Andreas has stated, that with the large number of
new file system options and layouts with ext4, mke2fs -S is much more
hazardous unless you __really__ know what you are doing.  It would
probably be a good idea to have some warning messages to that effect
in the man page.

						- Ted

</pre>
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    <br>
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