mmcblk0p8 new partition for data

There is a 7.5G partition on my jetson tk1 called mmcblk0p8

Can I format that and use that for data without effecting installed ubuntu?

Use parted mmcblk0. Keep in mind that this will almost certainly be destroyed the next time you flash!

Once in “parted” you will want to “print” to get a list of the partitions.

Remove partition 8 with rm 8 inside of “parted”.

Then add a new partition 8 mkpartfs within “parted”. It will ask for the partition name, for filesystem type (default is ext2) and it will want Start and End to be specified. Cut and paste the Start and End data from when you listed the partitions with “print” within “parted”.

Once this is done, exit “parted” and you can FSCK and mount that partition.

Keep in mind: when you flash the system again, you are almost certain to lose this. So be prepared and back up everything you don’t want to lose!

also see
if you are like me, and don’t like to unnecessarily fragment disk space into partitions