Beaglebone Black : Get More Space From Your SD Card

sandisk-micro-8While researching for my post, “Backing up your Beaglebone Black“, I came across an article that demonstrated how to expand the linux partition from the standard image size.  I use an 8GB card and after flashing my sd card with the Ubuntu image, I had roughly 4GB of unused space.  Since space is at a premium, I have added external USB drives to help with that but leaving 4GB on the table is just silly.  So I decided to fix that today.

Even though I’m doing this on an Ubuntu instance, this should work for Angstrom instances as well.  However, be forewarned that this is potentially dangerous for your file system.  Make backups, double-check your work, and test this out on an install you can afford to lose before doing it on one you can’t.  Warning over.  Let’s get back to throwing caution to the wind.

First, let’s take a look at what we’re working with.  As root, run:

fdisk -l

This will spit out a list of all the partitions on your BBB.  The one we are concerned with today is mmcblk0.

Now, using the fdisk utility, we can resize the card while in the BBB.  We’re going to delete the existing partition, then create a new one, expanding its size and then wrap it all up with a bow on top.

Let’s start with:

fdisk /dev/mmcblk0

You will get a prompt:

Command (m for help):

If you’re curious, enter ‘m‘.  You should be safe here, just don’t enter ‘w‘ which is write! If you’re unsure at any time, you can enter ‘q‘ to bail without committing.

Here’s the sequence to resize the card:

root@ubuntu-armhf:~# fdisk /dev/mmcblk0

Command (m for help): d
Partition number (1-4): 2

Command (m for help): n
Partition type:
 p primary (1 primary, 0 extended, 3 free)
 e extended
Select (default p): p
Partition number (1-4, default 2): 2
First sector (4096-15523839, default 4096): <enter>
Using default value 4096
Last sector, +sectors or +size{K,M,G} (4096-15523839, 
default 15523839): <enter>
Using default value 15523839
Command (m for help): w

The partition table has been altered!
Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: 
Device or resource busy. The kernel still uses the old table. 
The new table will be used at the next reboot or after you run 
partprobe(8) or kpartx(8)
Syncing disks.


Now, since the partition is currently in use, we won’t see any change until we reboot. Let’s do that now:

shutdown -r now

When the BBB comes back, you will have a 4GB partition in an 8GB partition.  We can fix that with a utility called resize2fs.  Here’s how to use it.  As root run this command:

resize2fs /dev/mmcblkp2

When this command completes, reboot again and then run ‘df -h‘.  Here’s what mine looks like:

dfrey@ubuntu-armhf:~$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mmcblk0p2 7.3G 1.4G 5.6G 20% /
none 4.0K 0 4.0K 0% /sys/fs/cgroup
devtmpfs 248M 4.0K 248M 1% /dev
none 50M 244K 50M 1% /run
none 5.0M 0 5.0M 0% /run/lock
none 248M 0 248M 0% /run/shm
none 100M 0 100M 0% /run/user
/dev/mmcblk0p1 1004K 472K 532K 48% /boot/uboot

Personally, I think this is a better solution than the USB drive but the USB drive works for backups and supporting content like MP3s, videos etc to host on my WordPress site. Space is still at a premium but at least now I have a little more breathing room.