How do I move a MySQL data directory to an external hard drive? I tried moving MySQL data directory to an external Hard disk (which has been formatted using NTFS).
I followed the steps given in the answer to the question How to change MySQL data directory?

Stop MySQL
Copy MySQL data directory to new location
Edit the MySQL configuration file (update datadir variable).
Update the new path in apparmor
Reload apparmor
Start MySQL (/etc/init.d/mysql restart)

But at the 6th step, when I restart MySQL it's failing. When I look into /var/log/mysql/error.log I get the following message:

2015-05-17 12:07:05 4317 [Warning] Can't create test file /media/prasanth/SeagateExpansionDrive/MWDatabase/mysql/    neo.lower-test
/usr/sbin/mysqld: Can't change dir to '/media/prasanth/SeagateExpansionDrive/MWDatabase/mysql/' (Errcode: 13 -     Permission denied)

What should I do to fix this problem?
I guessed that it is because the mysql user does not have permissions to write to the directory on the external hard drive. So I tried to change the ownership of the entire path (chown mysql:mysql -R /media/prasanth/SeagateExpansionDrive/MWDatabase/mysql/). But it didn't get reflected.
So I tried mounting that partition again with sudo mount -t ntfs -o rw,auto,user,fmask=0022,dmask=0000 /dev/sdb1 /media/prasanth/SeagateExpansionDrive/ with no luck.
Setup Details:
Host - Ubuntu 14.04
External Drive: NTFS FileSystem, 4TB single partition
MySQL: mysqld  Ver 5.6.19-0ubuntu0.14.04.1 for debian-linux-gnu on x86_64
The new directory must be accessible by mysqld.  In step 2, did you copy all ownership and permissions?
But probably you started mysqld as a user without permissions to the new directory?  Note that it can't even do a cd:  &quot;Can't change dir&quot;.
Check for SELinux or AppArmor being in the way.