resize2fs: Device or resource busy while trying to open /dev/mmcblk0p3

Question

I need to duplicate SD for RPI, but if I use 32G SD than it might not fit on other 32G SD, so I'm forced to use 16G SD, but than I loose half of the SD size.

I followed the instruction in How can I resize my / (root) partition?

I was able to resize the partition to the full disk size but when I do

sudo resize2fs /dev/mmcblk0p3

I get:

resize2fs 1.43.3 (04-Sep-2016)
resize2fs: Device or resource busy while trying to open /dev/mmcblk0p3
Couldn't find valid filesystem superblock.

I wasn't able to continue from there, or to find any info about this issue.

I'm confused about how is it possible to change a fs while you are using it, I guess the answer is that you cannot, but the answer in How can I resize my / (root) partition? claim it should work.

The other thing I don't understand is how could it be so difficult to find info about resizing an img to fit the SD? it seems like a very basic actioned, as in my case for example.

This is the result of sudo fdisk /dev/mmcblk0 (before extending the partition):

Disk /dev/mmcblk0: 14.9 GiB, 15931539456 bytes, 31116288 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00013bb5

Device         Boot   Start      End  Sectors  Size Id Type
/dev/mmcblk0p1 *          1   125000   125000   61M  c W95 FAT32 (LBA)
/dev/mmcblk0p2       125001  4882812  4757812  2.3G 83 Linux
/dev/mmcblk0p3      4884480 31116287 26231808 12.5G 83 Linux

This is the result of df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/mmcblk0p2  2.2G  592M  1.5G  29% /imgpart
/dev/loop0      260M  260M     0 100% /static
overlay          13G  3.3G  8.3G  29% /
devtmpfs        475M     0  475M   0% /dev
tmpfs           486M     0  486M   0% /dev/shm
tmpfs           486M  8.6M  477M   2% /run
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           486M     0  486M   0% /sys/fs/cgroup
tmpfs           486M   32K  486M   1% /tmp
tmpfs           486M     0  486M   0% /var/spool/cups
tmpfs            20M  524K   20M   3% /var/log
tmpfs           486M     0  486M   0% /var/spool/cups/tmp
/dev/mmcblk0p1   61M   35M   26M  58% /boot
tmpfs            98M     0   98M   0% /run/user/1000

NOTE: I'm running Volumio, and the / is mounted to partition 3 (I'm not sure why it show up as overlay)

Answer 1

There are two problems with your attempt. You try to expand

rpi3 ~$ sudo resize2fs /dev/mmcblk0p3

This is partition 3 on your SD Card. A default up to date Raspbian image only has two partitions:

/dev/mmcblk0p1   vfat32   boot partition
/dev/mmcblk0p2   ext4     root partition

There is no swap partition anymore. You should double check your partition numbers.

The accepted answer in How can I resize my / (root) partition? advises you to recreate the root partition. This was OK in 2012 but since that time it has changed something in addressing partitions in /boot/cmdline.txt and in /etc/fstab. If you use a disk partitioner like fdisk or parted it is possible that PARTUUID has changed and your SD Card will not boot. Maybe you have to edit /boot/cmdline.txt and /etc/fstab and change the partition names to /dev/mmcblk0p1 and /dev/mmcblk0p2. Further information about this issue you can find at Is it possible to use partition UUID for root-parameter in cmdline.txt?.

Answer 2

@guest's suggestion above worked for me. I'm running Xbian (which uses btrfs) and needed to modify the command for xbian's file structure. Here's what I used:

sudo btrfs filesystem resize max /home/xbian

Worked like a charm.

Answer 3

in answer to your second question:

You can use piclone to copy an (expanded or not-expanded) filesystem on a 32GB sd card onto another 32GB sd card. just install it with

sudo apt-get install piclone

then run it by typing piclone.(you have to have a GUI(desktop) running.)

Hope this answers your second question, I'm not positive this was the answer your looking for...