Re: How do you wipe a UBI filesystem?

On 2025-02-05, Grant Edwards <invalid@invalid.invalid> wrote:

Pretend I've got an MTD partition attached as a UBI device.
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That UBI device contains a couple differen UBI volumes.
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In one of those volumes is a UBIFS filesystem that has a bunch of
files in it.
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I've done some googling, but all of the answers are "use
ubiformat". That will wipe the whole device. I just want to
re-initialize one ubifs filesytem in one volume -- not the whole
ubi device.
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How do I wipe that filesystem (set it back to empty).  Do I need to
create an empty ubifs "image" file using mkfs.ubifs and then use
ubiupdatevol to write that image to the volume?
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Isn't there a simpler way?

I've figured out two other ways to do it:

    ubiupdatevol -t /dev/ubiX_Y
    mount -t ubifs /dev/ubiX:volname /mnt/point

That works, but apparently that erases every block in the
volume. That's a lot of unecessary wear.  Surely you can "empty" the
filesystem without erasing every block in the volume (when probably
90% of the blocks have never been written).

Another option:

    ubirmvol /dev/ubiX -N volname
    umimkvol /dev/ubiX -N volname -m
    mount -t ubifs /dev/ubiX:volname /mnt/point

That too seems to work, but modifying the devices volume table/list
seems a bit risky compared to simply re-initializing the filesystem
inside an existing volume.