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On a Raspberry Pi with the raspbian distro i need to make an extra partition that can be read from both windows and linux.

So i use FDISK on /dev/mmcblk0 (the sd card) to create a new partition which is a FAT32 partition like so

Device         Boot   Start      End  Sectors   Size Id Type
/dev/mmcblk0p1           16   125055   125040  61.1M  b W95 FAT32
/dev/mmcblk0p2       125056  2000000  1874945 915.5M 83 Linux
/dev/mmcblk0p3 *    2000001 15523839 13523839   6.5G  c W95 FAT32 (LBA)

After i have written the above and rebooted the device there is no extra drive or anything listed like the above partition, which i determine by using the df -h command:

Filesystem      Size  Used Avail Use% Mounted on
/dev/root       885M  442M  384M  54% /
devtmpfs        483M     0  483M   0% /dev
tmpfs           487M     0  487M   0% /dev/shm
tmpfs           487M  6.5M  481M   2% /run
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           487M     0  487M   0% /sys/fs/cgroup
tmpfs           487M     0  487M   0% /tmp
/dev/mmcblk0p1   61M   35M   27M  57% /boot
tmpfs            98M     0   98M   0% /run/user/0

The partition needs to be visible inside the linux terminal (mounted) and also visible if i pull out the card and plug it into a windows pc

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  • df -h only prints mounted filesystems. What does file -s /dev/mmcblk* tell you? (you need to run that as root, you do not need to umount anything to be able to run that) – grochmal Jul 26 '16 at 21:53
  • it lists the all the partitions, including /dev/mmcblk0p3: data but nothing more about mmcblk0p3 – Daniel Jørgensen Jul 26 '16 at 22:16
  • That looks fine, it is a partition alright then. But did you actually create a filesystem on the partition? e.g. mkfs.vfat -F 32 /dev/mmcblk0p3 – grochmal Jul 26 '16 at 22:38
  • if i write mkfs vfat -F 32 /dev/mmcblk0p3 it returns this output mkfs.ext2: invalid blocks '/dev/mmcblk0p3' on device '32'. I cannot write mkfs.vfat as that gives me command not found – Daniel Jørgensen Jul 26 '16 at 22:47
  • Figured that the reason for the command not found was because i needed dosfstools. Got that and now the command worked it seems as i got no errors when i ran the command you mentioned. But i still dont see it in df -h . Do i need to do anything further? – Daniel Jørgensen Jul 26 '16 at 22:52
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As we discussed the issue was that fdisk does not create a filesystem, it only creates partitions.

To create a FAT32 filesystem on raspbian you need to install dosfstools and then use mkfs.vfat as follows:

mkfs.vfat -F 32 <device>

In this specific case

mkfs.vfat -F 32 /dev/mmcblk0p3

After this the device is mountable.

Note: FAT32 has no uid/gid or access permissions written to the files on the filesystem. Therefore you may want to use the -o option of mount to use the files as a normal user. For example

mount -o uid=myuser /dev/mmcblk0p3 /home/myuser/mymountpoint
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