I'm using Ubuntu 14.04 from external hard-drive. Sometimes, when I run ubuntu "the disk drive for /tmp is not ready" error message appears and OS cannot be started. In this case, I restart several times to open ubuntu. Is there way to eliminate this problem?
The solution for this on a normal machine would be to add
/etc/fstab like this:
tmpfs /tmp tmpfs defaults 0 0
But there was a fix for mountall for 13.04. If you do have this it could be the external disk is just too slow.