step 1 : SD card format and partition

  • In this program, you are going to learn

  • How to find the SD card device name ?

  • How to delete existing partitions ?

  • How to add two partitions ?

  • How to format the partitons ?

  • How to mount the partitons ?

Topics in this section,

  • Clear the dmesg

$ sudo dmesg -c

  • After inserting the SD card reader to the Linux desktop machine, find its device name by dmesg.

$ dmesg | tail
[20194.951893] usb 1-3: Manufacturer: Prolific Technology Inc.
[20194.953283] pl2303 1-3:1.0: pl2303 converter detected
[20194.953986] usb 1-3: pl2303 converter now attached to ttyUSB0
[20195.422420] pl2303 ttyUSB0: pl2303_get_line_request - failed: -32
[20195.422975] pl2303 ttyUSB0: pl2303_get_line_request - failed: -32
[20213.618087] mmc0: cannot verify signal voltage switch
[20213.743845] mmc0: new ultra high speed SDR104 SDHC card at address aaaa
[20213.744562] mmcblk0: mmc0:aaaa SC16G 14.8 GiB

$ ls /dev/mmcblk0
/dev/mmcblk0

  • Remove and Add SD card and check the dmesg, do ls /dev/, check output and confirm your device ID

  • Startup fdisk in the administrative mode with the command sudo fdisk /dev/mmcblk0

$ sudo fdisk /dev/mmcblk0

Welcome to fdisk (util-linux 2.31.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help):

  • Enter d to delete any given partition name from the system.

Command (m for help): d
Partition number (1,2, default 2):

  • The next prompt will ask for the Partition number. Just press Enter to accept the default value.

Partition number (1,2, default 2):

Partition 2 has been deleted.

Command (m for help):

  • Enter d to delete any given partition name from the system.

Command (m for help): d
Selected partition 1
Partition 1 has been deleted.

Command (m for help):

  • Now, use the p command to print the partitions to verify.

Command (m for help): p
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: 0x5452574f

Command (m for help):

  • Finally, enter the w command to write the partitions out.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

  • Startup fdisk in the administrative mode with the command sudo fdisk /dev/mmcblk0

$ sudo fdisk /dev/mmcblk0

Welcome to fdisk (util-linux 2.34).
Changes will remain in memory only, until you decide to write them.
Be careful before using t1he write command.


Command (m for help):

  • Within fdisk, use the n command to create a new partition.

Command (m for help): n
Partition type
p   primary (0 primary, 0 extended, 4 free)
e   extended (container for logical partitions)
Select (default p):

  • Then we enter p to specify that the new partition will be a primary partition.

Select (default p):

Using default response p.
Partition number (1-4, default 1):

  • Next we select 1 to specify the partition number.

Partition number (1-4, default 1):
First sector (2048-31116287, default 2048):

  • The next prompt will ask for the first sector. Just press Enter to accept the default value.

First sector (2048-31116287, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-31116287, default 31116287):

  • After that it will ask for the last sector. Give the value as 512M

Last sector, +sectors or +size{K,M,G,T,P} (2048-31116287, default 31116287): +512M

Created a new partition 1 of type Linux and of size 512 MiB.
Partition #1 contains a vfat signature.

Do you want to remove the signature? [Y]es/[N]o: Y

The signature will be removed by a write command.


Command (m for help):

  • Now you have to type n to create new partition.

Command (m for help): n
Partition type
p   primary (1 primary, 0 extended, 3 free)
e   extended (container for logical partitions)
Select (default p):

  • Then type p for making a primary partition

Select (default p):

Using default response p.
Partition number (2-4, default 2):

  • Next we select 2 to specify the partition number.

Partition number (2-4, default 2):
First sector (1050624-31116287, default 1050624):

  • The next prompt will ask for the first sector. Just press Enter to accept the default value.

First sector (1050624-31116287, default 1050624):
Last sector, +sectors or +size{K,M,G,T,P} (1050624-31116287, default 31116287):

  • After that it will ask for the last sector. Give the value as 512M.

Last sector, +sectors or +size{K,M,G,T,P} (1050624-31116287, default 31116287): +512M

Created a new partition 2 of type 'Linux' and of size 512 MiB.
Partition #2 contains a ext4 signature.

Do you want to remove the signature? [Y]es/[N]o: Y

The signature will be removed by a write command.

Command (m for help):

  • Enter t to recognize specified partition table type.

Command (m for help): t
Partition number (1,2, default 2):

  • Next we select 1 to specify the partition number.

Partition number (1,2, default 2): 1
Hex code (type L to list all codes):

  • Enter b to change type of partition from Linux to FAT32.

Hex code (type L to list all codes): b

Changed type of partition 'Linux' to 'W95 FAT32'.

Command (m for help):

  • Now, use the p command to print the partitions to verify.

Command (m for help): p
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: 0x5452574f

Device         Boot   Start     End Sectors  Size Id Type
/dev/mmcblk0p1         2048 1050623 1048576  512M  b W95 FAT32
/dev/mmcblk0p2      1050624 2099199 1048576  512M 83 Linux

Filesystem/RAID signature on partition 1 will be wiped.
Filesystem/RAID signature on partition 2 will be wiped.

Command (m for help):

  • Finally, enter the w command to write the partitions out.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

  • FAT32 for boot partition

$ sudo mkfs.vfat -F 32 -n boot /dev/mmcblk0p1
mkfs.fat 4.1 (2017-01-24)
mkfs.fat: warning - lowercase labels might not work properly with DOS or Windows

  • ext4 for root partition

$ sudo mkfs.ext4 -L root /dev/mmcblk0p2
mke2fs 1.44.1 (24-Mar-2018)
Discarding device blocks: done
Creating filesystem with 131072 4k blocks and 32768 inodes
Filesystem UUID: a88d6d66-108a-40de-b740-7c55b4850db1
Superblock backups stored on blocks:
        32768, 98304

Allocating group tables: done
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

  • Mount both partitions so that we can write to them.

$ sudo mount /dev/mmcblk0p1 /mnt/boot
$ sudo mount /dev/mmcblk0p2 /mnt/root

Is fdisk the only command for managing partitions in Linux?

See Answer

  • ??

How do I start fdisk in Linux?

See Answer

  • ??

How to see the size of your Partition?

See Answer

  • ??

What are all file systems that is supported by u-boot?

See Answer

  • ??

Why we are using the FAT32 file system here?

See Answer

  • ??

Can we use any other file system instead of FAT32?

See Answer

  • ??

What is the purpose of mounting ?

See Answer

  • ??