What is in this unmounted partition and what is it used for?

Max2Play Home 2016 (en) Forums General Questions on Hardware and Max2Play Versions What is in this unmounted partition and what is it used for?

This topic contains 2 replies, has 2 voices, and was last updated by  Heiner Moderator 1 week, 3 days ago.

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  • 10. August 2019 at 16:21 #46745

    I have just cloned my M2P image to a new card which is larger so I went to expand the partition but there’s an unexpected partition (Partition 3) there. What’s it for? It’s not swap, mounted, not recognised as EXT and won’t mount when manually attempted.

    # fdisk -l
    Device Boot Start End Sectors Size Id Type
    /dev/mmcblk0p1 8192 93813 85622 41.8M c W95 FAT32 (LBA)
    /dev/mmcblk0p2 94208 15123840 15029633 7.2G 83 Linux
    /dev/mmcblk0p3 15123841 15523839 399999 195.3M 83 Linux

    # lsblk
    NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
    mmcblk0 179:0 0 14.9G 0 disk
    ├─mmcblk0p1 179:1 0 41.8M 0 part /boot
    ├─mmcblk0p2 179:2 0 7.2G 0 part /
    └─mmcblk0p3 179:3 0 195.3M 0 part

    # mount /dev/mmcblk0p3 /mnt/test/
    mount: wrong fs type, bad option, bad superblock on /dev/mmcblk0p3,
    missing codepage or helper program, or other error

    In some cases useful info is found in syslog – try
    dmesg | tail or so.

    # fsck /dev/mmcblk0p3
    fsck from util-linux 2.29.2
    e2fsck 1.43.4 (31-Jan-2017)
    ext2fs_open2: Bad magic number in super-block
    fsck.ext2: Superblock invalid, trying backup blocks…
    fsck.ext2: Bad magic number in super-block while trying to open /dev/mmcblk0p3

    The superblock could not be read or does not describe a valid ext2/ext3/ext4
    filesystem. If the device is valid and it really contains an ext2/ext3/ext4
    filesystem (and not swap or ufs or something else), then the superblock
    is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>
    or
    e2fsck -b 32768 <device>

    # swapon -s
    Filename Type Size Used Priority
    /var/swap file 102396 0 -2

    12. August 2019 at 15:07 #46758

    So I scanned the partition and every single byte was blank. I guess that’s to be expected on an unmounted partition…
    So I deleted the partition and resized using the expand filesystem function from within M2P web UI which resized it AND created the mystery partition again. I wrote the image back to the card that I had saved, resized the partition using raspi-config and no extra partition.
    So this seems to be something that you have implemented that is either by design or has a bug. If it’s by design can you please elaborate what it is for? If it’s a bug, that’s in V2.48 so feel free to squash for future releases 🙂

    15. August 2019 at 10:44 #46778

    Hi justinj,

    Thanks for your detailed posts. I’ll go through it with our head developer.

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