Creating mkfs for my custom filesystem

[Sankar P]

Thank you everyone for the plenty of good pointers. I should be able
to proceed from here :-)

On Fri, Mar 29, 2013 at 7:31 PM, Tobias Boege <tobias at gambas-buch.de> wrote:
> On Fri, 29 Mar 2013, Sankar P wrote:
>> On Fri, Mar 29, 2013 at 3:28 PM, Tobias Boege <tobias at gambas-buch.de> wrote:
>> > On Fri, 29 Mar 2013, Sankar P wrote:
>> >> Hi,
>> >>
>> >> I am trying to write a simple filesystem to learn the basics of it.
>> >>
>> >> I have decided on a simple layout for my filesystem where the first
>> >> block will be the super block and   will contain the version
>> >> information etc. The second block will contain the list of inodes.
>> >> Third block onwards will be data blocks. Each file can grow only up to
>> >> a single block size. Thrid block will represent the first file, fourth
>> >> block for the second file and so on. Directories will not be
>> >> supported.
>> >>
>> >> Now I want to create a mkfs for my filesystem as mentioned above. But
>> >> I am not able to find out how to do the mkfs for my filesystem such
>> >> that the generic mkfs utility will understand my filesystem. What APIs
>> >> should I be using ?
>> >>
>> >> Any help is appreciated. Thanks.
>> >
>> > According to my copy of the mkfs sources, you just have to create a program
>> > named "mkfs.ID" where ID identifies your filesystem. Then put that program
>> > in a location that the generic mkfs can find, i.e. under $PATH (mkfs seems
>> > to make some additions to PATH but you should figure this out yourself).
>> >
>> > Finally, calling "mkfs -t ID" makes mkfs search for a program named
>> > "mkfs.ID" - simple concatenation.
>> >
>>
>> oh okay. But how do I create the superblock ? What are the APIs
>> available to do these block level operations from a user space
>> application (my mkfs program ) ?
>>
>
> Look at how other mkfs.* do it. In general, these programs seem to be fairly
> complex. To interface with block devices from userspace: use the standard
> system calls, open(), lseek(), write(), ...
>
> For an example, you can look at the e2fsprogs source code. If you get
> through the jungle of indirections you will eventually find just a plain
> write() call in lib/ext2fs/unix_io.c:raw_write_blk() which is used for data
> transfer.
>
> Regards,
> Tobi
>
>
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-- 
Sankar P
http://psankar.blogspot.com