If you have an existing partition layout, for instance an image, and want to transfer it to a larger disk / SD Card, you might want to resize the last partition after writing the image, for using all available space.
Please note that this tutorial probably needs to be adjusted for dealing with extended partitions (if you have more than 4 partitions it is very probable that you have extended partitions).
You can do this from Linux using the command line:
Listing available block devices
lsblk
Will show you the available block devices. If your device is not listed, you may need to trigger USB / device recognition before re-running the command.
udevadm trigger
Note which /dev/sdx your drive is located at. (lsblk will also list the available partitions)
Repartition the SD card
Let’s assume that your SD card is located at /dev/sdc.
fdisk -u=sectors -l /dev/sdc
This command will list the partitions currently on the drive and exit. Example output (16 GB card with 8 GB image, last partition to be resized):
Disk /dev/sdc: 15.8 GB, 15819866112 bytes
4 heads, 32 sectors/track, 241392 cylinders, total 30898176 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
Disk identifier: 0×00003638
Device Boot Start End Blocks Id System
/dev/sdc1 4096 147455 71680 c W95 FAT32 (LBA)
/dev/sdc2 151552 15353855 7601152 83 Linux
Note the number of available partitions, the start (151552 in this case) of the last partition, the Id of the partition (83).
Now run the following command, to enter interactive mode of fdisk:
fdisk -u=sectors /dev/sdc
Pressing “m” + Enter will show you the available options. “q” + Enter will exit the application. No changes to the actual partition table will be done, until you write it (in the last step).
We will now delete and recreate the last partition, in our case it is partition number 2.
Press “d” + Enter
Enter “2” + Enter
Press “p” + Enter to list the result (not written yet to the SD, don’t worry – if you deleted the wrong partition, press “q” + Enter)
To recreate the last partition press “n” + Enter.
It will ask you for the partition type. Here you should press “p” + Enter (needs to be adjusted for extended partitions!)
On the second question, you can simply press enter – it will use “2” by default (or a different number if you have more partitions).
Now it will ask you for the first sector. Here you have to enter the exactly same value as the one you obtained with the first command. In our case it is 151552 . Press Enter.
Now it will ask you for the last sector. To resize to the maximum available space, simply press Enter to use the suggested default value.
Press “p” + Enter to check the result. It looks like this for us:
Command (m for help): p
Disk /dev/sdc: 15.8 GB, 15819866112 bytes
4 heads, 32 sectors/track, 241392 cylinders, total 30898176 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
Disk identifier: 0×00003638
Device Boot Start End Blocks Id System
/dev/sdc1 4096 147455 71680 c W95 FAT32 (LBA)
/dev/sdc2 151552 30898175 15373312 83 Linux
Check that the Id is the same as before, and that Start is also the same.
If you are satisfied with the result, press “w” and Enter to write the table. It will indicate the sucessful write by:
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
You can now exit the application by pressing “q” + Enter.
If you are NOT satisfied with the result, press “q” + Enter to exit the application without writing the new partition table.
At this point you can also use lsblk to see the success of the resize in human readable format.
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdc 8:32 1 14.8G 0 disk
├─sdc1 8:33 1 70M 0 part
└─sdc2 8:34 1 14.7G 0 part
Resizing File System
As the last step we need to resize the file system on the partition. For a Linux partition this is easily done in the following way:
resize2fs -p /dev/sdc2
will resize the partition to the maximum available space. It will acknowledge the success by:
resize2fs 1.42.5 (29-Jul-2012)
Resizing the filesystem on /dev/sdc2 to 3843328 (4k) blocks.
Begin pass 1 (max = 60)
Extending the inode table XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
The filesystem on /dev/sdc2 is now 3843328 blocks long.
That’s it.
Easy, once you know how to do it.
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