I think I found the source of my problems:
Apparently, ext4 filesystem has unlimited scalability (up to 4 billion) for the number of inodes it can have. However, there is a default inode count for every file system when it is created.
so I ran a df -i and got this:
I did a little more reading and discovered that inode count cannot be altered after the filesystem has been created.
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/sda6 915712 195691 720021 22% /
none 506099 866 505233 1% /dev
none 507229 7 507222 1% /dev/shm
none 507229 47 507182 1% /var/run
none 507229 1 507228 1% /var/lock
none 507229 1 507228 1% /lib/init/rw
/dev/sda7 5152768 5152768 0 100% /home
So this means I will have to format /home and recreate it with the new inode count, right?
One question on backing up files:
I have a large external backup that uses NTFS filesystem. Can I back up my ext4 files to that drive and still get them back afterwards (i.e. In the transfer, will the files transform from ext4 to NTFS? and vice versa)?
My plan is to use rsync -av to copy the files over.