MKFS.JFFS2 util

MKFS.JFFS2 util

[Nikhil]

hi all,

I am a bit confused whether i need to use mkfs.jffs2 when i need to save
data files on flash in jffs2 format, or is it fine to just mount flash
partition as jffs2 and simply copy the file from another storage(e.g. hard
disk)

i had a txt file on /home/mydir/test.txt which i need to have it on flash
in JFFS2 format. 

i followed the following steps.
1) mount the partition as JFFS2 (mount -t jffs2 /dev/mtdblock0 /mnt/cf)
and 
2) then copy the file (cp /home/mydir/test.txt /mnt/cf/) or 

1) i can MKFS.JFFS2 on the dir (mkfs.jffs2 -d /home/mydir/ -o myimage) 
2) then dd it to flash (dd if=myimage of=/dev/mtdblock0)
3) and then mount it (mount -t jffs2 /dev/mtdblock0 /mnt/cf/)

is the first method the correct way of implementation, as i am getting the
same results either way but i need not use mkfs.jffs2. if yes, then when
shud i use mkfs.jffs2 utility 




-- 
Thanks & Regards

Nikhil Shirodkar
Project Engineer
NISG, CDAC

Re: MKFS.JFFS2 util

[Ferenc Havasi]

Hi Nikhil,

> i followed the following steps.
> 1) mount the partition as JFFS2 (mount -t jffs2 /dev/mtdblock0 /mnt/cf)
> and 
> 2) then copy the file (cp /home/mydir/test.txt /mnt/cf/) or 
> 
> 1) i can MKFS.JFFS2 on the dir (mkfs.jffs2 -d /home/mydir/ -o myimage) 
> 2) then dd it to flash (dd if=myimage of=/dev/mtdblock0)
> 3) and then mount it (mount -t jffs2 /dev/mtdblock0 /mnt/cf/)
> 
> is the first method the correct way of implementation, as i am getting the
> same results either way but i need not use mkfs.jffs2. if yes, then when
> shud i use mkfs.jffs2 utility 

If before the first method the flash was empty (for example erased with 
flash_eraseall -j /dev/mtd/0) then the result will be the same in 
practice. Not exactly the same, but in practice it is the same.

When can be mkfs.jffs2 very usefull? For example:
- when the machine is very slow. With mkfs.jffs2 you can build the file 
system on a host machine which can be much faster.
- when there is no other possibility: in some cases it is impossible to 
simply copy files from somewhere, because there is no other storage 
devices. For example at HP iPAQ there is only a bootloader communicating 
via serial port. You can upload file system image (created by 
mkfs.jffs2), and the bootloader will simply write to the flash.

Ferenc