Re: Hacking linux-utils for swap label

[Loiseleur Michel <mloiseleur@linagora.com>]

Erik Mouw a écrit :

>On Thu, Apr 13, 2006 at 11:00:45AM +0200, Loiseleur Michel wrote:
>  
>
>>Here is the problem :
>>   I need a way in shell script to get back the device name from the 
>>label name, in order to restore (ie: format) it correctly in a recovery 
>>solution (mondorescue).
>>   For instance, a call to "e2label" do the job for the ext2/3 kind of 
>>partition.
>>   But for swap partition, there is _no_ way to get it back. The name 
>>didn't appear in /proc/swaps or /proc/partitions.
>>    
>>
>
>That's because filesystem labels is a userland issue and not at all
>kernel related. It's also how mount label works: the userland program
>"mount" figures out which device contains the requested label and
>passes the correct device to the mount() syscall.
>
>  
>
>>Here is my current hacking:
>>   I have developped myself a small "addon" to swapon/swapoff program, 
>>named _swaplabel_, which display the list of device, uuid and name of 
>>all the partitions. It was really easy, this code is old but so damn cool !
>>
>>Here is the question :
>>   1) Is this possible to enhance linux-utils in order to do the job ?
>>   2) What's the better way to correct this :
>>       2.1) a new program as my "swaplabel" ?
>>    
>>
>
>Yes, but rather name it something like dumpswap, just like dumpe2fs,
>etc.
>  
>
This is not exactly what I need. I don't know how to dress the full map 
of a swap file/partition, and I don't need it. I just need to retrieve 
the link between 'device' and 'label' put in /etc/fstab. After reading 
the code in linux-utils package (mount/swapon.c & 
mount/get_label_uuid.c), I figured out how to implement it in C. But I 
need it in shell script >_<.
The program I want to add is nearer of e2label program (ext2/3 
equivalent). That's why I suggested the name "swaplabel", which would be 
functionally equivalent to e2label.

>  
>
>>       2.2) a new option to swapon ? (there is already a "-l" in it, 
>>but it does not display the label)
>>    
>>
>
>No, mount also doesn't display labels.
>  
>
ok

>  
>
>>       2.3) a patch to the "-l" option ?
>>       2.4) a patch to add a colum "label" in /proc/partitions ?
>>    
>>
>
>No, cause labels are a userland issue.
>  
>
Yes, you're right. I wanted to join linux-utils developers, and it's the 
mailing list which seems the good one for me.


Thanks for your advice, erik.



-- 
Michel Loiseleur

-
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html