Resizing mtd partition

Ricard Wanderlof ricard.wanderlof at
Mon Feb 23 00:14:02 PST 2015

On Sun, 22 Feb 2015, Alexander Aronsky wrote:

> Hi everyone,
> I have to resize an existing mtd partition on a NOR flash of an embedded
> device (PPC architecture) without losing the data on this partition.
> To be more specific, I have /dev/mtd0 and /dev/mtd1 devices on my flash,
> and I want to increase the size of the file system mounted on /dev/mtdblock0
> at the expense of the one on /dev/mtdblock1. For example, eliminate the
> /dev/mtd1 altogether and give the /dev/mtd0 all the available space on the
> flash.
> What is the proper way to do it?

I don't think there is a 'proper' way, i.e. a resize application.

However, if the file system on the partition is jffs2, then I believe one 
could do the following:

- Unmount /dev/mtd0 (and /dev/mtd1)
- Erase /dev/mtd1
- Rewrite the partitioning info so that /dev/mtd0 now includes both
- Mount /dev/mtd0 .

When /dev/mtd0 is mounted, jffs2 will now see that the size is 
larger. Since there is no global file system information within a jffs2 
file system, it will see the newly erased space as unused when scanning 
the partition during the mount operation.

If you can't unmount /dev/mtd0 because it is the root file system, 
you could do most operations with /dev/mtd0 mounted, and a reboot in 

- Unmount /dev/mtd1.
- Erase /dev/mtd1.
- Rewrite partitioning info so that /dev/mtd0 new includes both old 
- Reboot the system, when it starts it will use the new larger 
  /dev/mtd0 .

Ricard Wolf Wanderlöf                           ricardw(at)
Axis Communications AB, Lund, Sweden  
Phone +46 46 272 2016                           Fax +46 46 13 61 30

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